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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..dead687 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #65173 (https://www.gutenberg.org/ebooks/65173) diff --git a/old/65173-0.txt b/old/65173-0.txt deleted file mode 100644 index 2a5ec05..0000000 --- a/old/65173-0.txt +++ /dev/null @@ -1,4627 +0,0 @@ -The Project Gutenberg eBook of USFWS Circular 16: Migration of Birds -(1950), by Frederick C. Lincoln - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: USFWS Circular 16: Migration of Birds (1950) - -Author: Frederick C. Lincoln - -Release Date: May 01, 2021 [eBook #65173] - -Language: English - -Character set encoding: UTF-8 - -Produced by: Tom Cosmas from materials made available on The Internet - Archive. - -*** START OF THE PROJECT GUTENBERG EBOOK USFWS CIRCULAR 16: MIGRATION OF -BIRDS (1950) *** - - - - -Transcriber's Note - -Emphasized text is denoted by _Italics_ and =Bold=. - - - - -[Illustration] - -MIGRATION of BIRDS - -[Illustration] - - -CIRCULAR 16 - -FISH AND WILDLIFE SERVICE - -UNITED STATES DEPARTMENT OF THE INTERIOR - - - - -MIGRATION of BIRDS - -[Illustration] - - -By FREDERICK C. LINCOLN - -_Biologist_ - -Illustrated by BOB MINES - - - -CIRCULAR 16 - - - UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, _Secretary_ - - FISH AND WILDLIFE SERVICE, Albert M. Day, _Director_ - -[Illustration] - - -UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1950 - -For sale by the Superintendent of Documents, Washington 25, D. C. -Price 30 cents - - - - -Contents - - - Page - - The mystery of migration 4 - - Advantages of migration 6 - - The origin of migration 7 - Northern ancestral home theory 8 - Southern ancestral home theory 8 - Theory of photoperiodism 9 - Theory of continental drift 11 - - When birds migrate 11 - Movements of species and groups 12 - Nocturnal and diurnal migration 15 - - How birds migrate 18 - Speed of flight and speed of migration 18 - Altitude at which birds travel 26 - Orientation 28 - Segregation during migration 31 - - Where birds migrate 34 - Short and undetermined migrations 34 - Variable migrations within species 35 - Fall flights not far south of breeding ranges 37 - Long-distance migrations 38 - - Routes of migration 41 - Wide and narrow migration lanes 42 - The fly ways 46 - Atlantic oceanic route 48 - Atlantic coast route and tributaries 53 - Mackenzie Valley--Great Lakes--Mississippi Valley Route and - tributaries 60 - Great Plains--Rocky Mountain routes 62 - Pacific coast route 63 - Pacific oceanic route 66 - Arctic routes 68 - - Evolution of migration routes 70 - - Vertical migration 72 - - Vagrant migration 73 - - Perils of migration 75 - Storms 75 - Aerial obstructions 76 - Exhaustion 78 - - Influence of the weather on migration 80 - - Problems of migration 81 - Banding studies 81 - Movements of residents 82 - Migration of the white-throated sparrow 84 - Migration of the yellow-billed loon 84 - - Conclusions 85 - - Appendix I--List of birds mentioned in the text 87 - - Appendix II--Bird banding 92 - - Bibliography 94 - - Index 99 - - - - -MIGRATION of BIRDS - - -When the birds that have nested in our dooryards and those that have -frequented the neighboring woods, hills, and marshes leave us in the -fall, the question naturally comes to mind: Where do they go? This, -however, is only one small part of the question as we also wonder: -Will the same ones return next spring to their former haunts? What -dangers will they face on their round-trip flight and while in their -winter homes? These and other questions on the migratory habits -of most species of Northern Hemisphere birds puzzle all who are -interested in them, whether it be the farmer who profits by their -tireless warfare against the weed and insect pests of his crops, -the bird student who enjoys an abundance and variety of feathered -inhabitants about him, or the hunter who wants a continuation from -year to year of the sport of wildfowling. Lack of information on the -subject may mean the loss of an important resource by unconsciously -letting it slip from us, as ignorance might be responsible for -inadequate legal protection for such species as might urgently -need it. More general knowledge on the subject will aid in the -perpetuation of the various migrants, the seasonal habitats of some -of which are in grave danger from man's utilization, sometimes -unwisely, of the marsh, water and other areas that were formerly -homes for birds. - -The migrations of birds were probably among the first natural -phenomena to attract the attention and intrigue the imagination of -man. Recorded observations on the subject date back nearly 3,000 -years, to the times of Hesiod, Homer, Herodotus, Aristotle, and -others. In the Bible there are several references to the periodic -movements of birds, as in the Book of Job (39:26), where the inquiry -is made: "Doth the hawk fly by Thy wisdom and stretch her wings -toward the south?" Jeremiah (8:7), wrote: "The stork in the heavens -knoweth her appointed time; and the turtle [dove], and the crane, and -the swallow, observe the time of their coming." And the flight of -quail that saved the Israelites from starvation in their wanderings -in the wilderness of Sinai is now recognized as a vast movement of -migratory quail between their breeding grounds and their winter home -in Africa. - -Throughout the ages the return flights of migratory birds have -been important as a source of food after a lean winter and as the -harbinger of a change in season. The arrival of certain species -has been heralded with appropriate ceremonies in many lands, and -among the Eskimos and other tribes the phenomenon to this day is -the accepted sign of the imminence of spring and of warmer weather. -The pioneer fur traders in Alaska and Canada offered rewards to the -Indian or Eskimo who saw the first goose of the spring, and all -joined in jubilant welcome to the newcomer. - -As the North American Continent became more thickly settled, the -large flocks of ducks and geese that always had been hunted for food -became objects of the enthusiastic attention of an increasing army -of sportsmen. Most of the nongame species were found to be valuable -also as allies of the farmer in his never-ending warfare against weed -and insect pests. The need for laws protecting the valuable game -and nongame birds and for regulating the hunting of the diminishing -game species followed as a natural course. In the management of this -wildlife resource it has become obvious that continuous studies -must be made of the food habits of the various species, their -environmental needs, and their travels. Hence bird investigations are -made by the Fish and Wildlife Service, the bureau charged by Congress -under the Migratory Bird Treaty Act with the duty of protecting those -species that in their yearly journeys pass back and forth between the -United States and Canada, and between the United States and Mexico. - -For more than half a century the Fish and Wildlife Service and -its predecessor, the Biological Survey, have been collecting data -on the interesting and important phenomenon of the migration of -North American birds. The field men of the Service have gathered -information concerning the distribution and seasonal movements of -the different species in many extended areas, from the Arctic coast -south to the pampas of Argentina. Supplementing these investigations -is the work of hundreds of volunteer ornithologists and bird students -throughout the United States and Canada, who each year, spring and -fall, forward to the Service reports on the migrations as observed in -their respective localities. Added to the mass of data thus assembled -is a rapidly growing recovery file of marked individuals. These -data, together with other carded records gleaned by the Fish and -Wildlife Service from a vast literature, constitute a series of files -that now contain well over 3,000,000 entries, easily the greatest -existing accumulation of information pertaining to the distribution -and movements of North American birds. Not only do the facts thus -assembled form the basis of regulatory action for the protection -of the birds, but they also make it possible to publish scientific -accounts of the ranges and migrations of the different species. They -furnish the basis of this bulletin. - -The several important bird-protective measures adopted by State and -Federal Governments, particularly those having as their objectives -the conservation of the migratory song, insectivorous, and game -species, can be effective only if they have intelligent public -support. To increase such support, information must be more generally -available on that little understood but universally fascinating -subject of bird migration. A brief presentation of facts on the -migratory habits of the birds scientifically gathered by the Fish -and Wildlife Service over many years, will be helpful to bird-study -classes, to conservation organizations, and to farmers and others -individually interested in the welfare of the birds. - -In addition to his original investigations in the field and in the -files of the Fish and Wildlife Service, the author has made free use -of the writings of many other students of the subject. To all of -these grateful acknowledgment is made. - - - - -_The Mystery of Migration_ - - -Of observers whose writings are extant, Aristotle, naturalist and -philosopher of ancient Greece, was one of the first to discuss the -subject of bird migration. He noted that cranes traveled from the -steppes of Scythia to the marshes at the headwaters of the Nile, -and that pelicans, geese, swans, rails, doves, and many other -birds likewise passed to warmer regions to spend the winter. In -the earliest years of the Christian era, the elder Pliny, Roman -naturalist, in his Historia Naturalis, repeated much of what -Aristotle had said on migration and added comments of his own -concerning the movements of the European blackbird, the starling, and -the thrushes. - -In spite of the keen perception shown in some of his statements -Aristotle also must be credited with the origin of some superstitious -beliefs that persisted for several centuries. One of these, that -of hibernation, became so firmly rooted that Dr. Elliott Coues -(1878),[1] one of America's greatest ornithologists, listed the -titles of no less than 182 papers dealing with the hibernation -of swallows. The hibernation theory accounted for the autumnal -disappearance of certain species of birds by having them pass into -a torpid state and so remain during the cold season, hidden in -hollow trees, caves, or in the mud of marshes. Aristotle ascribed -hibernation not only to swallows, but also to storks, kites, doves, -and others. Some early naturalists wrote fantastic accounts of the -flocks of swallows that allegedly were seen congregating in the -marshes until their accumulated weight bent into the water the -reeds on which they clung and thus submerged the birds. It was even -recorded that when fishermen in northern waters drew up their nets -they sometimes had a mixed "catch" of fish and hibernating swallows. -Clarke (1912) quotes Olaus Magnus, Archbishop of Upsala, who in 1555 -published a work entitled "Historia de Gentibus Septentrionalis et -Natura," wherein he observed that if swallows so caught were taken -into a warm room they would soon begin to fly about but would live -only a short time. - - [1] Publications referred to parenthetically by date are listed - in the Bibliography, p. 94. - -The hibernation theory survived for more than 2,000 years and, until -the winter home of the chimney swift was discovered in 1944 through -the recovery of banded individuals, it was occasionally repeated -by credulous persons to account for the sudden disappearance of -the immense flocks that each autumn gather in southern Georgia and -northern Florida. Although the winter range is still unknown in -fullest detail, Lincoln (1944b) has shown that some of these birds -spend the winter season in northeastern Peru. - -Although the idea that hibernation is a regular feature of the life -cycle of birds is no longer accepted for any species, recognition -must be accorded the observations of Edmund C. Jaeger of Riverside -College, Riverside, Calif. (1949). Earlier (1948), he had given a -brief account of the behavior of a poor-will found during the winter -of 1946-47 in the Chukawalla Mountains of the Colorado Desert, -Calif., and which was in a state of profound torpidity. - -What was presumably the same individual was found in the same rock -niche in a comatose condition on November 26, 1947. Beginning on -December 30, 1947, rectal temperatures were taken every 2 weeks, the -last on February 14, 1948. The temperature dropped from 67.6° on the -first date to 64.4° on January 18 and February 1, recovering to 65.8° -on the late date of record. The weight decreased from 45.61 grams on -January 4 to 44.56 grams on February 14. An attempt to detect heart -beat by the use of a medical stethoscope was negative. No movement of -the chest walls could be detected and no moisture could be collected -on a cold mirror placed in front of the nostrils. Strong light aimed -directly into the pupil resulted in no response, not even an attempt -to close the eyelid. No waste matter was passed during the entire -period of observation and all evidence indicated that the bird was in -an exceedingly low state of metabolism. - -This bird was banded on January 5, 1948, with a Service band and -was back in the same rock niche on November 24, 1948, certainly -the second and probably the third season of return to this exact -point. It was there on December 5, 1948, but 2 weeks later it had -disappeared, probably the victim of some predator or an inquisitive -human. Professor Jaeger reports that the Hopi Indians call the -poor-will "Holchko," the sleeping one. - -Aristotle also was the originator of the theory of transmutation, -basing it upon the fact that frequently one species will arrive -from the north just as another species departs for more southerly -latitudes. From this he reasoned that although it was commonly -believed that such birds were of two different species, there really -was only one, and that this one assumed the different plumages to -correspond with the summer and winter seasons. - -Probably the most remarkable theory that has been advanced to account -for migration is contained in a pamphlet mentioned by Clarke (1912: -V. I, 9-11) as published in 1703 under the title: "An Essay Toward -the Probable Solution of this Question: Whence come the Stork and -the Turtle, the Crane, and the Swallow, when they Know and Observe -the Appointed Time of their Coming." It was written "By a Person of -Learning and Piety," whose "probable solution" was that migratory -birds flew to the moon and there spent the winter. - -Some peoples, who easily accepted the migratory travels of the larger -birds, were unable to understand how the smaller species, some of -them notoriously poor fliers, could make similar journeys. They -accordingly conceived the idea that the larger species, as the storks -and cranes, carried their smaller companions as living freight. In -some of the Mediterranean countries, it is still believed that these -broad-pinioned birds serve as aerial transports for the hosts of -small birds that congregate upon the shores awaiting opportunity for -this kind of passage to their winter homes in Africa. Similar beliefs -have been found among some tribes of North American Indians. - - - - -_Advantages of Migration_ - - -Before presenting some of the present theories concerning the origin -of bird migration, it seems well to consider briefly the ends that -are served by this annual round trip between breeding grounds and -winter quarters. It is apparent that the migratory habit enables a -species to enjoy the summers of northern latitudes while avoiding the -severity of the winters. In other words, migration makes it possible -for some species to inhabit two different areas during the seasons -when each presents favorable conditions. In the performance of its -reproductive duties, every pair of birds requires a certain amount of -territory, the extent of which varies greatly in different species. -Generally, however, this territory must be large enough to provide -adequate food, not only for the parent birds, but also for the lusty -appetites that come into being with the hatching of the eggs. Thus, -if all birds were to remain constantly either in tropical or in -temperate regions, there would be intolerable overcrowding during the -breeding season. By the spring withdrawal to regions uninhabitable -earlier in the year, the migrants are assured of adequate space and -ample food upon their arrival in the winter-freed North, and it may -be assumed that the nonmigratory species that are resident in the -South are also benefited by the departure of the migrants. - -Nevertheless, it cannot be said that the winter or summer area of -every species is entirely unsuited to its requirements at other -seasons, for some individuals pass the winter season in areas that -are frequented only in summer by other individuals of their species. -Such species have extensive breeding ranges, presenting wide climatic -variations, so that some individuals may actually be resident in a -region where others of their kind are present only in winter. - -The tendency of some birds to move southward at the approach of -winter is not always due to the seasonal low temperatures, since -experiments have demonstrated that many of our summer insect feeders, -when confined in outdoor aviaries, comfortably withstand temperatures -far below zero. The main consideration is the depletion of the food -supply, caused either by the disappearance or the hibernation of -insects, or by the mantle of snow or ice that prevents access to the -seeds and other forms of food found on or close to the ground or -submerged in water. Possibly also the shortened hours of daylight -materially restrict the ability of the birds to obtain sufficient -food at a time when the cold requires an increased supply to maintain -body heat. It is noteworthy that some of our smaller birds, such -as the chickadees, have no fear of Arctic weather, as their food -supplies are entirely arboreal and so are always available. Also, -when there is a good supply of food in the form of pine and spruce -seeds, nuthatches and crossbills will remain through the winter in -Canadian woods. When these birds appear abundantly in winter at -points in southern latitudes, it may be concluded that there is a -shortage of their food in the North. - - - - -_The Origin of Migration_ - - -Migration has long since become a definite hereditary habit that -recurs in annual cycles, probably because of physiological stimulus -associated with the reproductive period. Its origin is locked in the -ages of geologic time, but by study of the history of how birds came -to occupy their present ranges, information becomes available from -which reasonable theories may be developed and explored. The two that -are most commonly accepted are diametrically opposed to each other. - - -=Northern ancestral home theory= - -According to one of these hypotheses, in earlier ages nonmigratory -birds swarmed over the entire Northern Hemisphere. At that time the -conditions of food and habitat were such as to permit them to remain -in their haunts throughout the year, that is, the entire northern -area then afforded the two important avian requirements--suitable -breeding conditions, and year-long food supply. This is the condition -today in the Tropics, and it is noteworthy that, as a rule, tropical -birds do not perform migrations. Gradually, however, in the Northern -Hemisphere the glacial ice fields advanced southward, forcing the -birds before them, until finally all bird life was concentrated -in southern latitudes. As the ages passed the ice cap gradually -retreated, and each spring the birds whose ancestral home had been in -the North endeavored to return, only to be driven south again at the -approach of winter. As the size of the ice-covered area diminished -the journeys made became ever longer until eventually the climatic -conditions of the present age became established and with them the -habit of migration. - -Thus, this theory supposes that today migratory birds follow the path -of a great racial movement that took place in a distant past and was -associated with the advances and recessions of the ice. The actions -of the birds themselves lend some support to this theory, as every -bird student has noted the feverish impatience with which certain -species push northward in spring, sometimes advancing so rapidly upon -the heels of winter that they perish in great numbers when overtaken -by late storms. It is probable that at this season the reproductive -impulse is a determining factor in driving the birds to their -northern breeding grounds. - - -=Southern ancestral home theory= - -The opposing theory is simpler in some respects and supposes that the -ancestral home of all birds was in the Tropics and that, as all bird -life tends to overpopulation, there was a constant effort to seek -breeding grounds where the competition would be less keen. Species -that strove for more northern latitudes were kept in check by the ice -and were forced to return southward with the recurrence of winter -conditions. Gradually, as the ice retreated, vast areas of virgin -country became successively suitable for summer occupancy, but the -winter habitat remained the home to which the birds returned after -the nesting season. It is a fact that some species spend very little -time on their breeding grounds; the orchard oriole, for example, -spends only 2½ months in its summer home, arriving in southern -Pennsylvania about the first week in May and leaving by the middle of -July. - -Both of these theories assume that migration is an ingrained habit, -but both have been criticized on biological and geological grounds, -so neither should be accepted without qualification as definitely -accounting for the origin of bird migration. It is apparent, however, -that whether the ancestral home of any species was at the northern or -southern limits of its present range, or even in some intermediate -region, the search for favorable conditions under which to breed in -summer and to feed in winter has been the principal factor underlying -the origin of migration. - - -=Theory of photoperiodism= - -A modern view based on studies of living behavior, suggests also that -there is good reason for believing that migration is an annually -induced movement. If such be true then the theory of photoperiodism -as propounded by some recent investigators should receive some -consideration. - -This theory holds as its major premise that quantity of light and -length of day are the stimulating causes of migration. Its proponents -urge that migration is a phenomenon far too regular to be created -anew each season merely under stress of circumstances, such as need -for food; and that it begins before the necessity for a change in -latitude becomes at all pressing. Swallows, nighthawks, shore birds, -and others may start their southward movement while the summer food -supply in the North is at peak abundance; while robins, bluebirds, -and others may leave an abundant food in the South in spring and -press toward northern points when food supplies there are almost -entirely lacking and when severe cold and storms are likely to cause -their wholesale destruction. The regularity of arrival and departure -is one of the most impressive features of migration, and since birds -travel in almost strict accordance with the calendar, the proponents -of the theory ask: "What phenomenon to which we may attribute the -stimulating impulse occurs with such precise regularity as the -constantly increasing amount of light in spring?" - -Experimental work has abundantly demonstrated the effect of increased -light upon the growth, flowering, and fruiting of plants. Similarly, -experiments with the common junco or snowbird reported by Rowan (1931: -121), resulted in increased development of the sexual organs by -the end of December, although the birds were confined in outdoor -aviaries in Canada, and had been exposed to temperatures as low as --44° F. From the first of November until early in January, the juncos -were subjected to ever-increasing light, supplied in the aviaries by -electric bulbs. As regards illumination, they were thus artificially -provided with conditions approximating those of spring. At the close -of this period, it was found that the sexual organs of the birds had -attained the maximum development normally associated with spring. -With gradual reduction of the lighting over a period of little more -than 1 month, the organs returned to their normal winter condition. - -After a consideration of all evidence, including the fact that no -ultra-violet rays were used, it was concluded that the explanation -lay in the increased exercise taken during the periods of increased -light. A simple test whereby certain birds were forced by mechanical -means to take more exercise, the light being so reduced that there -was merely sufficient glow for them to see the advancing mechanism -that forced them into movement, showed that the rate of development -of the sexual organs exactly paralleled that in the birds that were -exposed to extended periods of illumination in the outdoor aviaries. -Other features in this experiment--such as the behavior of the birds -themselves--also indicated that more activity due to increased light -is the governing cause of the spring development of the sexual -organs. If this development be accepted as a controlling cause of -migration, then this experiment must be recognized as of great -importance. - -Upon closer analysis, however, it is found that this theory, like -those before discussed, is open to serious objections. First, some of -our summer residents that migrate south for the winter do not stop -in equatorial regions, where they might find the periods of day and -night about equally divided, but push on beyond, some penetrating as -far south as Patagonia. Also it might be asked: "If the lengthening -day is the stimulating factor, why should our summer birds wintering -in the Tropics ever start northward, as in their winter quarters -the variation in the length of day from winter to summer is -imperceptible?" Like all the other theories advanced, this also, as -at present understood, is subject to unanswered criticism. - - -=Theory of continental drift= - -The theory of continental drift postulates an original northern land -mass, called Laurasia, and a southern one, called Gondwana. According -to this concept, each eventually broke into several segments which -eventually became the present continents. It is further assumed that -occasionally Laurasia and Gondwana drifted close to one another or -were at times in actual contact. On the basis of this geological -theory, Wolfson (1940) has attempted to explain the migrations of -some species of birds from one hemisphere to the other, as, for -example, the Greenland wheatear, Arctic tern, and several shore -birds (turnstone, sanderling, knot, golden plover, and others). -Acceptance of this hypothesis requires abandonment of the belief that -the development of migration was the result of useful ends that were -served thereby, and in its place, to give approval to the idea that -migration was merely "the natural consequence of an inherent behavior -pattern responding to the drifting of continental masses." - -It is a strange fact that although almost all professional -paleontologists are agreed that existing data oppose the theory of -continental drift, those who support it contend that their case is -strengthened by these same data. If, in the geologic history of the -earth, there was any such thing as continental drift, it appears -from the evidence available that it was before the Cretaceous -period, estimated to have been about 70,000,000 years ago. Birds had -then evolved but those known from fossil remains were of extremely -primitive types such as Hesperornis and Ichthyornis. There is no -evidence of the existence in that period of any birds that were -even closely related to any of those now living. Accordingly, it is -difficult to believe that the migratory patterns of existing species -have been determined by events that, if they did take place, were at -least 70,000,000 or more years ago. - - - - -_When Birds Migrate_ - - -It is known that at any given point many species leave in the fall -and return in the spring. Since banding has had such wide application -as a method of study, it is known also that in some species one of -the parent birds (rarely both) frequently returns and nests in the -tree, bush, or box that held its nest in the previous season. One -ordinarily thinks of the world of birds as quiescent during two -periods each year, at nesting time, and in winter. For individuals -this is obviously the case, but when the entire avifauna of the -continent is considered it is found that there are at almost all -periods some latitudinal movements. - - -=Movements of species and groups= - -Some species begin their fall migrations early in July and in some -parts of the country distinct southward movements can be detected -from then until the beginning or middle of winter. For example, -many shore birds start south in the early part of July, while the -goshawks, snowy owls, redpolls, Bohemian waxwings, and many others -do not leave the North until forced to do so by the advent of severe -winter weather, or by lack of the customary food. Thus an observer in -the northern part of the United States may record an almost unbroken -southward procession of birds from midsummer to winter, and note -some of the returning migrants as early as the middle of February. -While on their way north, purple martins have been known to arrive -in Florida late in January and, among late arrivals, the northern -movement may continue into the first week of June. In some species -the migration is so prolonged that the first arrivals in the southern -part of the breeding range will have performed their parental duties -while others of that species are still on their way north. - -A study of these facts indicates that sometimes there exists a very -definite relationship between what we may term northern and southern -groups of individuals of the same species. A supposition is that -for a species with an extensive latitudinal breeding range, and -which has a normal migration, those individuals that nest farthest -south migrate first and proceed to the southern part of the winter -range; those that occupy the central parts of the breeding range -migrate next and travel to regions in the winter range north of -those occupied by the first group; and finally the individuals -breeding farthest north are the last to start their autumn migration -and they remain farthest north during the winter. In other words, -this theory supposes that the southward movement of the species is -such that the different groups maintain their relative latitudinal -position with each other. The black and white warbler furnishes -an example. The breeding range of this bird extends west and -northwest from northern Georgia and South Carolina to New Brunswick, -extending also in a western and northwestern direction as far as -Great Bear Lake in northwestern Canada (fig. 1). It spends the -winter in southern Florida, the West Indies, central Mexico, Central -America, and northwestern South America. In the southern part of -its breeding range it is nesting in April, but those that summer in -New Brunswick do not reach their nesting grounds before the middle -of May. Therefore, about 50 days are required for these northbound -birds to cross the breeding range, and if 60 days be allowed for -nest building, egg laying, incubation, care of young, and molt, they -would not be ready to start southward before the middle of July -(fig. 2.). Then another 50-day trip south, and the earliest migrants -from the northern areas would reach the Gulf Coast in September. -But both adults and young have been observed at Key West, Fla., by -the middle of July, and on the northern coast of South America by -August 21. Since the birds at Key West were fully 500 miles south of -the breeding range, it is evident that they must have come from the -southern part of the nesting area. - -[Illustration: _Figure 1._--Summer and winter homes of the black -and white warbler, a very slow migrant as the birds nesting in the -northern part of the country take 50 days to cross the breeding -range. The speed of migration is shown in figure 2. (See p. 14.)] - -[Illustration: _Figure 2._--Isochronal migration lines of the black -and white warbler, showing a very slow and uniform migration. These -birds apparently advance only about 20 miles a day in crossing the -United States. (See p. 13.)] - -Many similar cases might be mentioned, such as the black-throated -blue warblers, which are still observed in the mountains of Haiti in -the middle of May, when others of this species are en route through -North Carolina to breeding territory in New England or have even -reached that region. Redstarts and yellow warblers, evidently the -more southern breeders, are seen returning southward on the northern -coast of South America just about the time that the earliest of -those breeding in the North reach Florida on their way to winter -quarters. - - -=Nocturnal and diurnal migration= - -When one recalls that most birds appear to be more or less helpless -in the dark, it seems remarkable that many should select the night -hours for extended travel. Among those that do, however, are the -great hosts of shore birds, rails, flycatchers, orioles, most of -the great family of sparrows, the warblers, vireos, and thrushes, -and in fact, the majority of small birds. That it is common to find -woods and fields on one day almost barren of bird life, and on the -following day filled with sparrows, warblers, and thrushes, would -indicate the arrival of migrants during the night. Sportsmen sitting -in their "blinds" frequently observe the passage of flocks of ducks -and geese, but great numbers of these birds also pass through at -night, the clarion call of the Canada goose, or the conversational -gabbling of a flock of ducks being common night sounds in spring and -fall in many parts of the country. The sibilant, nocturnal calls of -the upland plover or Bartramian sandpiper and of other shore birds -during their spring and fall flights form vivid memories in the minds -of many students of migration. Observations made with telescopes -focused on the full moon have shown processions of birds, one -observer estimating that birds passed his point of observation at the -rate of 9,000 an hour, which gives some indication of the numbers of -birds that are in the air during some of the nights when migration -is at its height. While the steady night-long passage of migratory -birds has been recorded, the bulk of the flocks pass during the -earlier hours of the evening and toward daylight in the morning, the -periods from 8 o'clock to midnight and from 4 to 6 a. m. seeming to -be favorite times for nocturnal flight. - -It has been claimed, with some reason, that small birds migrate -by night the better to avoid their enemies, and that most of the -nocturnal travelers are those that are naturally timid, sedentary, -or feeble-winged. To a certain extent this may be true as included -in this group are not only such weak fliers as the rails but also -the small song and insectivorous birds such as the wrens, the small -woodland flycatchers, and other species which, living habitually more -or less in concealment, are probably much safer making their flights -under the protecting cloak of darkness. Nevertheless, it must be -remembered that night migrants include also the snipe, sandpipers, -and plovers, birds that are always found in the open, and are among -the more powerful fliers, some of them making flights of more than -2,000 miles across the ocean. - -Night travel is probably best for the majority of birds chiefly -from the standpoint of feeding. Digestion is very rapid in birds -and yet the stomach of one killed during the day almost always -contains food. To replace the energy required for long flight, it is -essential that food be obtained at comparatively short intervals, the -longest of which in most species is during the hours of darkness. -If the smaller migrants were to make protracted flights by day they -would be likely to arrive at their destination at nightfall almost -exhausted, but since they are entirely daylight feeders, they would -be unable to obtain food until the following morning. This would -delay further flights and result in great exhaustion or possibly -even death were they so unfortunate as to have their evening arrival -coincident with unusually cold or stormy weather. Traveling at night, -they pause at daybreak and devote the entire period of daylight to -alternate feeding and resting. This permits complete recuperation and -resumption of the journey at nightfall. - -Many species of wading and swimming birds migrate either by day or -night, as they are able to feed at all hours, and are not accustomed -to seek safety in concealment. Some diving birds, including ducks -that submerge when in danger, sometimes travel over water by day and -over land at night. The day migrants include, in addition to some -of the ducks and geese, the loons, cranes, gulls, pelicans, hawks, -swallows, nighthawks, and the swifts. All of these are strong-winged -birds. The swifts, swallows, and nighthawks (sometimes called -bullbats) feed entirely on flying insects, and use their short, -weak feet and legs only for grasping a perch during periods of rest -or sleep. Thus they feed as they travel, the circling flocks being -frequently seen in late summer working gradually southward. Years ago -before birds of prey were so thoughtlessly slaughtered, great flocks -of red-tailed. Swainson's, and rough-legged hawks might be seen -wheeling majestically across the sky in the Plains States, and in the -East the flights of broad-winged. Cooper's, and sharp-skinned hawks -are still occasionally seen. To the birds of prey and possibly to the -gulls also, a day's fasting now and then is no hardship, particularly -since they frequently gorge themselves to repletion when opportunity -is afforded. - -[Illustration: _Figure 3._--Migration of the cliff swallow, a day -migrant that instead of flying across the Caribbean Sea as does the -blackpolled warbler (see fig. 6), follows around the coast of Central -America, where food is readily obtained. (See p. 25.)] - -An interesting comparison of the flights of day and night migrants -may be made through a consideration of the spring migrations of the -blackpolled warbler and the cliff swallow. Both spend the winter -in South America, at which season they are neighbors. But when the -impulse comes to start northward toward their respective breeding -grounds, the warblers strike straight across the Caribbean Sea -to Florida (fig. 6), while the swallows begin their journey by a -westward flight of several hundred miles to Panama (fig. 3.). Thence -they move leisurely along the western shore of the Caribbean Sea -to Mexico, and continuing to avoid a long trip over water, they -go completely around the western end of the Gulf of Mexico. This -circuitous route adds more than 2,000 miles to the journey of the -swallows that nest in Nova Scotia. The question may be asked: "Why -should the swallow select a route so much longer and more roundabout -than that taken by the blackpolled warbler?" The simple explanation -is that the swallow is a day migrant while the warbler travels at -night. The migration of the warbler is made up of a series of long, -nocturnal flights, alternated with days of rest and feeding in -favorable localities. The swallow, on the other hand, starts its -migration several weeks earlier and catches each day's ration of -flying insects during a few hours of aerial evolutions, which at the -same time carry it slowly in the proper direction. Flying along the -insect-teeming shores of the Gulf of Mexico, the 2,000 extra miles -that are added to the migration route are but a fraction of the -distance that these birds cover in pursuit of their daily food. - -Although most of our smaller birds make their longest flights at -night, close observation will show that travel is continued to some -extent by day. This is particularly true during the latter half of -a migratory season when the birds show evidence of an overpowering -desire to hasten to their breeding grounds. At this time flocks of -birds while feeding maintain a movement in the general direction of -the seasonal journey. Sometimes they travel hurriedly, and while -their flights may be short, they must cover an appreciable distance -in the course of a day. - - - - -_How Birds Migrate_ - - -=Speed of flight and speed of migration= - -There is a widespread misconception concerning the speed at which -birds normally fly, and even regarding the speed they can attain when -occasion demands, as when closely pursued by an enemy. It is not -unusual to hear accounts of birds flying "a mile a minute." While -undoubtedly some birds can and do attain a speed even greater than -this, such cases are exceptional, and it is safe to say that even -when pressed, few can develop an air speed of 60 miles an hour. They -do, however, have two speeds, one being the normal rate for everyday -purposes and also for migration, and an accelerated speed for escape -or pursuit; this in some cases may be nearly double the normal rate -of movement. Nevertheless, it is doubtful if the effort required for -the high speeds could be long sustained, and certainly not for the -long-distance migratory journeys that are regularly made by most -birds. The theory that migrating birds attain high speeds received -encouragement from the German ornithologist Gätke (1895), who for -many years made observations on birds at the island of Heligoland. -He postulated that the blue-throat, a species of thrush smaller than -the American hermit thrush, would leave African winter quarters at -dusk and reach Heligoland at dawn, which would mean a sustained speed -of 200 miles an hour, and that the American golden plover flew from -the coast of Labrador to Brazil in 15 hours, or at the tremendous -speed of 250 miles an hour. Most ornithologists now consider these -conclusions to be unwarranted. - -Sportsmen also often greatly overestimate the speed at which ducks -and geese fly and sometimes attempt to substantiate their estimates -by mathematical calculation, based upon the known velocity of a -charge of shot, the estimated distance and the estimated "lead" that -was necessary to hit the bird. If all three elements of the equation -were known with certainty, the speed of the bird could be determined -with a fair degree of accuracy. The majority of the ducks that are -reported as killed at 40, 50, or even 60 yards, however, actually -are shot at distances much less than estimated. To sight along a gun -barrel and estimate correctly the distance of a moving object against -the sky is so nearly impossible for the average gunner as to make -such calculations of little value. - -During the past few years reliable data on the speed of birds have -accumulated slowly. It has been found that a common flying speed -of ducks and geese is between 40 and 50 miles an hour, and that it -is much less among the smaller birds. Herons, hawks, horned larks, -ravens, and shrikes, timed with the speedometer of an automobile, -have been found to fly 22 to 28 miles an hour, while some of the -flycatchers are such slow fliers that they attain only 10 to 17 miles -an hour. Even such fast-flying birds as the mourning dove rarely -exceed 35 miles an hour. All these birds can fly faster, but it is to -be remembered that at training camps during World War I, airplanes -having a maximum speed of about 80 miles an hour easily overtook -flocks of ducks that, it may be supposed, were making every effort -to escape. Aviators have claimed that at 65 miles an hour they can -overtake the fastest ducks, though cases are on record of ducks -passing airplanes that were making 55 miles an hour. - -The greatest bird speeds that have been reliably recorded are of the -swifts and the duck hawk, or peregrine falcon. An observer in an -airplane in Mesopotamia reported that swifts easily circled his ship -when it was traveling at 68 miles an hour. To do this, the birds -certainly were flying at a speed as high as 100 miles an hour. Once -a hunting duck hawk, timed with a stop watch, was calculated to have -attained a speed between 165 and 180 miles an hour. - -The speed of migration, however, is quite different from that -attained in forced flights for short distances. A sustained flight of -10 hours a day would carry herons, hawks, crows, and smaller birds -from 100 to 250 miles, while ducks and geese might travel as much as -400 to 500 miles in the same period. Measured as air-line distances, -these journeys are impressive and indicate that birds could cover the -ordinary migration route from the northern United States or even from -northern Canada to winter quarters in the West Indies or in Central -America or South America in a relatively short time. It is probable -that individual birds do make flights of the length indicated and -that barn swallows seen in May on Beata Island, off the southern -coast of the Dominican Republic, may have reached that point after a -nonstop flight of 350 miles across the Caribbean Sea from the coast -of Venezuela. Nevertheless, whether they continue such journeys day -after day is doubtful. - -It seems more likely that migrations are performed in a leisurely -manner, and that after a flight of a few hours the birds pause to -feed and rest for one or several days, particularly if they find -themselves in congenial surroundings. Some indication of this is -found in the records of banded birds, particularly waterfowl. -Considering only the shortest intervals that have elapsed between -banding in the North and recovery in southern regions, it is found -that usually a month or more is taken to cover an air-line distance -of a thousand miles. For example, a black duck banded at Lake Scugog, -Ontario, was killed 12 days later at Vicksburg, Miss. If the bird was -taken shortly after its arrival, the record would indicate an average -daily flight of only 83 miles, a distance that could have been -covered in about 2 hours' flying time. Among the thousands of banding -records obtained in recent years, evidences of such rapid flight are -decidedly scarce, for with few exceptions all thousand-mile flights -have required 2 to 4 weeks or more. Among sportsmen, the blue-winged -teal is well known as a fast-flying duck and quite a few of these -banded on Canadian breeding grounds have covered 2,300 to 3,000 miles -in a 30-day period. Nevertheless, the majority of those that have -traveled to South America were not recovered in that region until -2 or 3 months after they were banded. Probably the fastest flight -over a long distance for one of these little ducks was one made by a -young male which traveled 3,800 miles from the delta of the Athabaska -River, in northern Alberta, Canada, to Maracaibo, Venezuela, in -exactly 1 month. This flight was at an average speed of 125 miles per -day. The greatest migration speed thus far recorded for any banded -bird is that of a lesser yellowlegs banded at North Eastham, Cape -Cod, Mass., on August 28, 1935, and killed 6 days later, 1,900 miles -away, at Lamentin, Martinique, French West Indies. This bird traveled -an average daily distance of more than 316 miles. - -It seems certain that migratory journeys are performed at the normal -rate of flight, as this would best conserve the strength of the birds -and eliminate the fatigue that would result from effort required for -great speed. Migrating birds passing lightships and lighthouses, or -crossing the face of the moon, have been observed to fly without -hurry or evidence of straining to attain high speed. - -The speed of migration also is demonstrated by the dates of arrival, -particularly during the spring movement. The Canada goose affords a -typical example of regular, but slow migration. Its advance northward -at this season is at the same rate as the advance of the season (fig. -4). In fact, the isotherm of 35° F. appears to be a governing factor -in the speed at which these geese move north, and over their entire -trip the vanguard follows closely the advance of this isotherm. - -Few species perform such regular migrations, many waiting in their -winter homes until spring is well advanced and then moving rapidly -to their breeding grounds. Sometimes this advance is so rapid that -the later migrants actually catch up with species that for a month or -more may have been pressing slowly but steadily northward. - -One of the best examples of rapid migration is found in the -gray-cheeked thrush. This bird winters in Colombia, Ecuador, Peru, -Venezuela, and British Guiana and does not start its northward -journey until many other species are well on their way. It does not -appear in the United States until the last of April--April 25 near -the mouth of the Mississippi, and April 30 in northern Florida (fig. -5). A month later, or by the last week in May, the bird is seen in -northwestern Alaska, the 4,000-mile trip from Louisiana having been -made at an average speed of about 130 miles a day. - -[Illustration: _Figure 4._--Migration of the Canada goose. The -northward movement keeps pace with the advance of spring, in this -case the advance of the isotherm of 35° F. agreeing with that of the -birds.] - -Another example of rapid migration is furnished by the yellow, or -summer, warbler. Coming from the Tropics, the birds reach New Orleans -about April 5, when the average temperature is 65° F. Traveling north -much faster than does the season, they reach their breeding grounds -in Manitoba the latter part of May, when the average temperature is -only 47°. Encountering progressively colder weather over their entire -route, they cross a strip of country in the 15 days from May 11 to 25 -that spring temperatures take 35 days to cross. This "catching up" -with spring is habitual in species that winter south of the United -States and in most of the northern species that winter in the Gulf -States. To this rule there appear to be only six exceptions--the -Canada goose, the mallard, the pintail, the crow, the red-winged -blackbird, and the robin. - -[Illustration: _Figure 5._--Isochronal migration lines of the -gray-cheeked thrush, an example of rapid migration. The distance -from Louisiana to Alaska is about 4,000 miles and is covered at -an average speed of about 130 miles a day. The last part of the -journey is covered at a speed that is several times what it is in the -Mississippi Valley.] - -The blue goose presents a striking example of a late but very rapid -spring migration. Practically all members of the species winter in -the great coastal marshes of Louisiana, where 50,000 or more may -be seen grazing in the "pastures" or flying overhead in flocks of -various sizes. Their breeding grounds are chiefly on Baffin Island -and on Southampton Island in the northern part of Hudson Bay, in a -region where conditions of severe cold prevail except for a few weeks -each year. The birds seem to realize that even though the season in -their winter quarters is advancing rapidly, their nesting grounds -are still covered with a heavy blanket of ice and snow. Accordingly -they remain in the coastal marshes until the last of March or the -first of April, when the local birds are already busily engaged with -the duties of reproduction. The flight northward is rapid, almost -nonstop, so far as the United States is concerned, for although the -birds are sometimes recorded in large numbers in the Mississippi -Valley, including eastern South Dakota, and in southeastern Manitoba, -there are few records anywhere along the route of such great flocks -as are known to winter in Louisiana. When the birds arrive in the -James Bay region of Canada they apparently enjoy a prolonged period -of rest, as they are not noted in the vicinity of their breeding -grounds until the first of June. During the first 2 weeks of that -month they pour into the tundra country by the thousands, and each -pair immediately sets about the business of rearing a brood. - -The robin has been mentioned as a slow migrant, and as a species it -takes 78 days to make the 3,000-mile trip from Iowa to Alaska, a -stretch of country that is crossed by advancing spring in 68 days. -In this case, however, it does not mean that individual robins are -necessarily slow, for probably the northward movement of the species -depends upon the continual advance of birds from the rear, the first -individuals arriving in a suitable locality remaining to nest, while -the northward movement of the species is continued by those still to -come. - -Special interest attaches to the great variation in the speed -at which birds travel in different sections of the broad flyway -extending from the Gulf of Mexico to the Arctic Ocean, by way of -the Mississippi and Mackenzie Valleys. The blackpolled warbler -furnishes an excellent example (fig. 6). This species winters in -north-central South America and migrates in April across the West -Indies to Florida. From this point some individuals fly northwest to -the Mississippi Valley, north to Manitoba, northwest to the Mackenzie -River, and thence almost due west to western Alaska. In tracing -the long route of these birds it is found that a fairly uniform -average speed of 30 to 35 miles a day is maintained from the Gulf to -Minnesota. Then comes a spurt, for a week later the blackpolls have -reached the central part of the Mackenzie Valley and by the following -week they are observed in northwestern Alaska. During the latter -part of the journey, therefore, many individuals must average more -than 200 miles a day. They use 30 days in traveling from Florida to -southern Minnesota, a distance of about 1,000 miles, and scarcely -half that time to cover the remaining 2,500 miles to Alaska. It -should be noted that the increased speed is directly associated -with the change in direction, the north-and-south course in the -Mississippi Valley being accomplished slowly while the northwesterly -course across Canada is made at a much greater speed. Increased -speed across western Canada to Alaska is also shown by many other -birds. A study of all species traveling up the Mississippi Valley -indicates an average speed of about 23 miles a day. From southern -Minnesota to southern Manitoba 16 species maintain an average speed -of about 40 miles a day. From that point to Lake Athabaska, 12 -species travel at an average speed of 72 miles a day; while 5 others -travel to Great Slave Lake at 116 miles a day; and another 5 species -cover 150 miles a day to reach Alaska. This change is in correlation -with a corresponding variation in the isothermal lines, which turn -northwestward west of the Great Lakes. - -[Illustration: _Figure 6._--Migration of the blackpolled warbler. The -solid isochronal lines show the places at which these birds arrive at -the same time. As the birds move northward these lines become farther -apart, showing that the warblers move faster with the advance of -spring. From April 30 to May 10 the average speed is about 30 miles -a day, while from May 25 to May 30 it is increased to more than 200 -miles.] - -As has been previously indicated, the advance of spring in the -northern interior is much more rapid than in the Mississippi Valley -and on the Gulf coast. In other words, in the North spring comes with -a rush and during the height of the migration season in Saskatchewan -the temperature in the southern part of the Mackenzie Valley just -about equals that in the Lake Superior area, which is 700 miles -farther south. Such conditions, coupled with the diagonal course of -the birds across this region of fast-moving spring, exert a great -influence on migration and are the chief factors in the acceleration -of speed of travel. - -Variations in speed of migration in different parts of the country -are illustrated also by the movements of the cliff swallow (fig. -3), which breeds from Mexico to Alaska and winters in Brazil and -Argentina. It would be expected in spring to appear in the United -States first in Florida and Texas then in the southern Rocky -Mountain region, and finally on the Pacific coast. As a matter of -fact, however, the earliest spring records come from north-central -California, where the bird usually is common before the first -arrivals are observed in Texas or Florida. The route taken, for many -years a migration problem, was solved when it was found that these -swallows went around the Gulf of Mexico rather than across it. The -isochronal lines on the map show the more rapid advance along the -Pacific coast. By March 20, when the vanguard has not quite reached -the lower Rio Grande in Texas, the species is already north of San -Francisco in California. - - -=Altitude at which birds travel= - -At one time students of bird migration held firmly to the theory -that normal migration takes place at heights above 15,000 feet, -reasoning (somewhat uncertainly) that flying becomes easier as -altitude is gained. Since the development of the airplane, however, -and with it man's exploration of the upper regions of the air, it -has become common knowledge that rarified atmosphere adds greatly to -the difficulties of flight. This is due not only to the reduction in -oxygen (whether for gasoline engine or the lungs of a bird) but also -to the lack of buoyancy of the rarified air. Such birds as vultures, -pelicans, cranes, and some of the hawks feel this the least, since -compared with body weight the supporting surface of their wings is -very great, but for the smaller and shorter-winged birds lack of -buoyancy at high altitudes presents a difficult obstacle in flight. -Even when flying close to the earth, small birds have to keep their -wings in rapid motion. - -Another postulate favoring the high-altitude flying theory was -that the wonderful vision of birds was their sole guidance during -migratory flights; and to keep landmarks in view the birds were -obliged to fly high, particularly when crossing wide areas of water. -This will be considered in greater detail under Orientation (p. 28), -so here it will be sufficient to say that birds rely only in part -upon vision to guide them on migration. Also, it is to be remembered -that there are definite physical limitations to the range of -visibility even under perfect atmospheric conditions. Chief of these -is the curvature of the earth's surface. Thus, if birds crossing the -Gulf of Mexico to Louisiana and Florida flew at a height of 5 miles, -they would still be unable to see a third of the way across. And yet -this trip is made twice each year by thousands of thrushes, warblers, -and others. - -Actual knowledge of the altitude of migratory flight is scanty, -though estimates obtained by means of the telescope, and still more -accurate data resulting from altimeter observation from airplanes, -are slowly accumulating. It is, of course, obvious that some birds -that cross mountain ranges during migration must attain a great -altitude. Observers at an altitude of 14,000 feet in the Himalayas -have recorded storks and cranes flying so high that they could be -seen only through field glasses. Being beyond the range of unaided -vision they must have been at least 6,000 feet above the observers, -or at an actual altitude of 20,000 feet above sea level. Such cases, -however, are exceptional as aviators have reported that they rarely -meet birds above an altitude of 5,000 feet. - -It is now known that migration in general is performed below a -height of 3,000 feet above the earth. Some proof of this statement -is available. Observations made from lighthouses and other points -of vantage indicate that migrants commonly travel at altitudes of a -very few feet to a few hundred feet above sea or land. Sandpipers, -sanderlings, and northern phalaropes, observed in migration on the -Pacific oceanic route, have been noted to fly so low that they -were visible only as they topped a wave. Observers stationed at -lighthouses and lightships off the English coast have similarly -recorded the passage of land birds, which sometimes flew just above -the surface of the water, and rarely above 200 feet. During the -World Wars broad areas in the air were under constant surveillance -and among the airplane pilots and observers many took more than a -casual interest in birds. Of the several hundred records resulting -from their observations only 36 were of birds flying above 5,000 -feet, and only 7 above 8,500 feet. Cranes were once recorded at -an altitude of 15,000 feet, while the lapwing was the bird most -frequently seen at high levels, 8,500 feet being its greatest -recorded altitude. - -These observations naturally relate only to daytime travelers, but -there is no reason to believe that nocturnal migration is performed -at higher altitudes. The fact that many birds are killed each year by -striking the lanterns at lighthouses, or other man-made obstructions, -does not, however, furnish conclusive proof that low altitudes are -generally used during nocturnal flight, for it should be recalled -that these accidents occur chiefly in foggy or unsettled weather, and -also that powerful lights have a great attraction for many species -of birds. The altitude at which birds travel is affected by other -weather conditions also. For example, flight at the higher elevations -is facilitated on clear, warm days by the currents of warm air that -ascend from broad areas. - - -=Orientation= - -There probably is no single aspect of the entire subject of bird -migration that challenges our admiration so much as the unerring -certainty with which birds cover thousands of miles of land and -water to come to rest in exactly the same spot where they spent -the previous summer or winter. The records from birds marked with -numbered bands offer abundant proof that the same individuals of many -species will return again and again to their identical nesting sites. -These data show also that many individuals migrate in fall over -the same route, year after year, making the same stops and finally -arriving at the precise thicket that served them in previous winters. - -The faculty that enables these birds to point their course accurately -over vast expanses of land and water may, for want of a better -term, be called a "sense of direction." Man recognizes this sense -in himself, though usually it is imperfect and frequently at fault. -Nevertheless the facility with which experienced hunters and woodsmen -locate tiny camps or other points in forested or mountainous country, -frequently cloaked by darkness or fog, with all recognizable -landmarks obliterated seems due to this faculty. Ability to travel -with precision over unmarked trails is not limited either to birds or -to man. It is likewise possessed by many other mammals as well as by -some insects and fishes, the well-known migrations of the salmon and -the eel being notable examples. - -Ability to follow a more or less definite course to a definite goal -is evidently part of an inherited faculty. Both the path and the goal -must have been determined either when the habit originated or in the -course of its subsequent evolution. The theory is sometimes advanced -that the older and more experienced birds lead the way, showing the -route to their younger companions. This explanation may be acceptable -for some species, but not for those in which adults and the young -migrate at different times. The young cowbird that is reared by -foster parents flocks with others of its kind when grown and in many -cases can hardly be said to have adult guidance in migration. An -inherited migratory instinct with a definite sense of the goal to -be reached and the route to be followed must be attributed to these -birds. - -It is well known that birds possess wonderful vision. If they also -have retentive memories subsequent trips over the route may well be -steered in part by recognizable landmarks. The arguments against the -theory of vision and memory are chiefly that much migration takes -place by night and that great stretches of the open sea are crossed -without hesitation. Nevertheless, the nights are rarely so dark that -all terrestrial objects are totally obscured, and such features as -coastlines and rivers are just those that are most likely to be -seen in the faintest light, particularly by the acute vision of the -bird and from its aerial points of observation. But some birds fly -unerringly through the densest fog. Members of the Biological Survey, -proceeding by steamer from the island of Unalaska to Bogoslof Island -in Bering Sea, through a fog that was so heavy as to make invisible -every object beyond a hundred yards, recorded the fact that flocks of -murres, returning to Bogoslof, after quests for food, broke through -the wall of fog astern, flew by the vessel, and disappeared into the -mists ahead. The ship was heading direct for the island by the use of -compass and chart, but its course was no more sure than that of the -birds. - -Some investigators have asserted that the sense of direction has its -seat in the ears or nasal passages and thus that the bird is enabled -to identify air currents and other phenomena. It has been found that -disturbance of the columella or the semicircular canals of the inner -ear will destroy the homing instinct of the racing pigeon, but -experiments in the form of delicate operations, or closing the ears -with wax, prove such a serious shock to the sensitive nervous system -of the bird that they cannot be considered as affording conclusive -evidence. Several years ago careful studies were made of the homing -instinct of the sooty and noddy terns, tropical species that in the -Atlantic region reach their most northern breeding point on the Dry -Tortugas Islands, off the southwest coast of Florida. They are not -known to wander regularly any appreciable distance farther north. -It was found that some were able to return to their nests on the -Tortugas after they had been taken on board ship, confined in cages -below decks, and carried northward to distances varying from 400 to -800 miles before being released. Landmarks of all kinds were entirely -lacking, and the birds certainly were liberated in a region in which -they had had no previous experience. - -Possibly the "homing instinct" as shown by these terns, by the -man-o'-war birds that are trained and used as message carriers in the -Tuamotu, Gilbert, and Marshall Islands, and by the homing pigeon, is -not identical with the sense of perceptive orientation that figures -in the flights of migratory birds. Nevertheless, it seems closely -akin and is probably caused by the same impulses, whatever they -may be and however they may be received. It should be remembered, -however, that while homing may involve flight from a point that -the bird has never before visited, the flight is always to a known -point--that is, the bird's nest--while, on the other hand, the first -migratory flight is always from the region of the bird's birth to a -region it has never before visited. The spring migration might, of -course, be more nearly considered as true "homing." - -Some students have leaned strongly toward the possible existence -of a "magnetic sense" as being the important factor in the power -of geographical orientation. The theory that migratory birds might -be responsive to the magnetic field of the earth was conceived as -early as 1855, when some experimental work was done in Russia, and -nearly 60 years later in France. Recently investigations in this -field have been conducted by Yeagley (1947) and by Gordon (1948) -with diametrically opposite results. The idea carries with it the -implication that contained in the bird's body is an organ that is -sensitive to the effect of its motion through the vertical component -of the magnetic field and to other related factors. In the tests by -Dr. Yeagley, 20 young homing pigeons were given training flights to -their home loft from distances up to 100 miles. Permanent magnets -were then affixed to the under side of the manus part of the wings -of half of the birds while copper plates of equivalent weight were -attached to the wings of the other half. All birds were released -singly at an air-line distance of about 65 miles from the loft. The -results were most suggestive, as only two of the birds carrying -magnets returned to the loft, whereas eight of the controls returned. - -With certain minor modifications, this experiment was repeated by -Gordon. In this case 60 pigeons were used and releases were made from -points up to 58 miles, where the direction of flight was such that -the birds had to navigate across the gradient of the magnetic field. -Every bird returned to its loft on the day of release regardless of -whether it carried magnets or unmagnetized bars of the same weight. - -Attempts to demonstrate the effect of radio waves on the navigational -ability of birds also have produced contradictory results. In some of -these tests, homing pigeons released near broadcasting stations have -appeared to be hopelessly confused, whereas in others, apparently -conducted in the same manner, no effects could be discerned. It is -obvious that before the electromagnetic theory can be accepted or -rejected, much additional experimental work is necessary. - -In concluding this discussion of orientation it is pertinent to -point out that the migratory instinct appears to be more or less -transitory, that it is not persistent over an extended period. -Migratory birds may be arrested en route, either by natural -conditions, such as unusual food supplies, or forcibly by the act of -man, and detained until the end or nearly the end of the migratory -season, and then may not attempt to finish the journey, apparently -having lost the migratory impulse. In the fall and early winter of -1929, abundant food and an open season caused an unusual number of -mallard ducks to arrest their migration and remain in western Montana -and northern Idaho. Later, however, a heavy snowfall with subzero -temperatures suddenly cut off the food supply, with the result that -great numbers of the birds starved to death, when a flight of a few -hours would have carried them to a region of open water and abundant -food. - - -=Segregation during migration= - -During the height of the northward movement in spring the woods -and thickets may be suddenly filled with several species of wood -warblers, thrushes, sparrows, flycatchers, and others, which -it is natural to conclude have traveled together and arrived -simultaneously. Probably they did, but such combined migration is by -no means the rule for all species. - -As a group the wood warblers (_Compsothlypidae_) probably travel more -in mixed companies than do any other single family of North American -birds. The flocks are likely to be made up of several species in -spring and fall with both adults and young. Sometimes swallows, -sparrows, blackbirds, and some of the shore birds also migrate in -mixed flocks. In fall, great flocks of blackbirds frequently sweep -south across the Plains States, and occasionally one flock will -contain bronzed grackles, red-winged blackbirds, yellow-headed -blackbirds, and Brewer's blackbirds. - -On the other hand many species keep strictly to themselves. It would -be difficult for any other kind of bird to keep in company with -one of such rapid movements as the chimney swift, which is rarely -found associated with any other species at any season. Nighthawks -or bullbats also fly in separate companies, as do usually crows, -waxwings, crossbills, bobolinks, and kingbirds. Occasionally, a flock -of ducks will be observed to contain several species, but generally -when they are actually on migration the individuals of each species -separate and travel with others of their own kind. The flocks of -blue geese, previously mentioned in connection with speed of flight -(p. 22), frequently have with them a few of the closely related snow -geese, particularly in the eastern part of their winter range. The -portion here is usually about 10 to 1, but farther west the numbers -of snow geese increase until they outnumber their blue relatives. - -The adults of most perching birds drive the young away when they are -grown, probably to be relieved of the necessity of providing for -them, and also in order that the parents may have opportunity to rest -and renew their plumage before starting for winter quarters. The -young birds are therefore likely to drift together and, having no -further responsibility, may start south ahead of their parents. In -contrast with this indifference on the part of the adults of perching -birds, Canada geese and some others remain in family groups, the -parent birds undergoing the wing molt that renders them flightless -during the period of growth of their young, so that old and young -acquire their full plumage at the same time and are able to start -south together. The large flocks, therefore, are composed of many -families that band together, and when they separate into =V=-shaped -units it is probably correct to assume that it is an old bird that -leads the group. Where there is segregation of the sexes, the young -birds usually accompany their mothers, as is the case with some of -the ducks. After the females start to incubate their eggs, the males -of most species of ducks flock by themselves and remain together -until fall. - -The males and females of some species may migrate either -simultaneously or separately. In the latter case it is usually the -males that arrive first, sometimes great flocks of male birds, as in -the red-winged blackbird, reaching a locality several days before any -of the females. This is particularly the rule in spring: The first -robins are usually found to be males, as are also the first song -sparrows, rose-breasted grosbeaks, and scarlet tanagers. This early -arrival of the males has been explained on the theory of territorial -possession, under which the male selects the area where it elects to -breed, each individual attempting to protect a definite territory -from trespass by other males of his own kind, at the same time -singing or otherwise announcing his presence and inviting the later -arriving female to examine the territory that he has selected for -nesting. The long-billed marsh wren is a noteworthy example, and the -males of this species may enthusiastically build several dummy nests -before the females arrive. - -In a few species the males and females apparently arrive at the -breeding grounds together and proceed at once to nest building. In -fact among the shore birds, ducks, and geese, courtship and mating -may take place in whole or in part while the birds are in the South -or on their way north, so that when they arrive at the northern -nesting grounds they are paired and ready to proceed at once with -the raising of their families. Mallards and black ducks may be -observed in pairs as early as January, the female leading and the -male following when they take flight. Naturally these mated pairs -migrate north in company, and it was largely to protect such species -that duck shooting in spring was abolished by Federal law a number of -years ago. - -Many shore birds nest well within the Arctic Circle, and it is the -opinion of ornithologists that most of these birds share, at least -in part, the habits of the phalaropes, a family in which the male -assumes the entire care of the eggs and young. If this be true, it -explains why in southern latitudes so many of the earliest fall -arrivals are females that may have deserted the breeding grounds -after the eggs were laid. - -Migratory flights are frequently accomplished in close flock -formation, as with the shore birds, blackbirds, and waxwings, and -especially some of the sparrows--the snow buntings, longspurs, -juncos, and tree sparrows. Other species, however, though they travel -in flocks, maintain a very loose formation; examples are the turkey -vultures, the hawks, swifts, blue jays, swallows, warblers, and -bluebirds. Still others, the grebes, great horned owls, winter wrens, -shrikes, and belted kingfishers for example, ordinarily travel alone -and when several are found in close proximity it is an indication -that they have been drawn together by unusual conditions, such as -abundant food. - - - - -_Where Birds Migrate_ - - -Definite evidence shows that both the length and the duration of the -migratory journey vary greatly. The bobwhite and the western quails, -the cardinal, the Carolina wren, and probably some of the titmice and -woodpeckers, which are apparently almost or quite nonmigratory, may -round out their full period of existence without at any time going -more than 10 miles from the nest where they were hatched. - - -=Short and undetermined migrations= - -Song sparrows, meadow larks, blue jays, and some other species make -such short migrations that the movement is difficult to detect, as -individuals may be found in one area throughout the year. Thus, at -the southern part of the range there is merely a concentration in -winter, the summer individuals being entirely sedentary. Speculation -is useless on the distances of individual migration without definite -evidence concerning the precise winter quarters of birds that summer -in a particular part of the breeding range of the species, but from -the records of banded birds important evidence is becoming available. -Eventually it may be possible to say definitely just how far the song -sparrows that nest in northern New England and the Maritime Provinces -of Canada travel to their winter quarters, and whether the blue jays -of New York and the upper Mississippi Valley remain throughout the -winter in their breeding areas, or move farther south and relinquish -their places to individuals from southern Canada. - -An illustration of what is now known on this subject is found in the -case of the robin. This bird occurs in the Middle Atlantic States -throughout the year, in Canada only in summer, and along the Gulf -coast only as a winter resident. On the Atlantic coast its movements -are readily ascertained, since, for example, in the section about -Washington, D. C., the breeding robin is the southern variety -(_Turdus migratorius archrusterus_) which is found there from the -first of April to the last of October, when its place is taken -(in smaller numbers) by the northern robin (_Turdus migratorius -migratorius_), which arrives about the middle of October and remains -until the following April. It is probable that a similar interchange -of individual robins occurs throughout a large part of the balance of -its range, the hardy birds from the north being the winter tenants in -the abandoned summer homes of the southern birds. - -The red-winged blackbirds that nest in northern Texas are almost -sedentary, but in winter they are joined by representatives of other -subspecies that nest as far north as the Mackenzie Valley. - - -=Variable migrations within species= - -The difference in characters between subspecies has been used by -students of migration to discover other interesting facts concerning -variations of the migratory flight between closely related birds -that breed in different latitudes. The familiar eastern fox sparrow -(_Passerella iliaca iliaca_) breeds from northwestern Alaska to -Labrador, and in winter is found concentrated in the southeastern -part of the United States. It thus travels a long distance each year. -On the west coast of the continent, however, six subspecies of this -bird breed in rather sharply delimited ranges, extending from the -region of Puget Sound and Vancouver Island to Unimak Island, at the -end of the Alaskan Peninsula. One of these, known as the sooty fox -sparrow (_P. i. fuliginosa_) breeds in the Puget Sound area and makes -practically no migration at all, while the other races, nesting on -the coast of British Columbia and Alaska, are found in winter chiefly -in California. The races that breed farthest north are in winter -found farthest south, illustrating a tendency for those birds that -are forced to migrate to pass over those so favorably located that -they have no need to leave their breeding areas, while the northern -birds settle for the winter in the unoccupied areas farther south -(fig, 7). - -Another example of the same kind is the Maryland yellowthroat of -the Atlantic coast. Birds occupying the most southern part of the -general range are almost nonmigratory, residing throughout the year -in Florida, while those breeding as far north as Newfoundland go to -the West Indies for the winter, thus passing directly over the home -of their southern relatives. - -[Illustration: _Figure 7._--Migration of Pacific-coast forms of the -fox sparrow. The breeding ranges of the different races are encircled -by solid lines, while the winter ranges are dotted. The numbers -indicate the areas used by the different subspecies, as follows: 1. -Shumagin fox sparrow; 2. Kodiak fox sparrow; 3. Valdez fox sparrow; -4. Yakutat fox sparrow; 5. Townsend fox sparrow; 6. Sooty fox -sparrow (After Swarth, courtesy of the Museum of Vertebrate Zoology, -University of California).] - -The palm warbler (_Dendroica palmarum_) which breeds from Nova -Scotia and Maine west and northwest to southern Mackenzie, has been -separated into two subspecies. Those breeding in the interior of -Canada (_D. p. palmarum_) make a 3,000-mile journey from Great Slave -Lake to Cuba, passing through the Gulf States early in October. After -the bulk have passed, the palm warblers from the Northeastern States -and Provinces (_D. p. hypochrysea_) drift slowly into the Gulf Coast -region, where they remain for the winter. Their migratory journey is -about half as long as that of the northwestern subspecies. - -There is no invariable law governing the distance of migration, -although in general it is found that where a species has an extensive -range, the subspecies that breed farthest north go farthest south to -spend the winter. - - -=Fall flights not far south of breeding ranges= - -Some other species that have extensive summer ranges, for instance -the pine warbler, rock wren, field sparrow, loggerhead shrike, and -black-headed grosbeak, are found to concentrate during the winter -season in the southern part of the breeding range, or to occupy -additional territory that is only a short distance farther south. -The entire species may thus be confined within a restricted area for -the period of winter, and then, with the return of warmer weather, -spreads out to reoccupy the full range. - -There are many species, including the tree sparrow, slate-colored -junco, and Lapland longspur, that nest in Canada and winter in the -United States; while others, including the vesper sparrow, chipping -sparrow, grackles, red-winged blackbirds, bluebirds, the woodcock, -and several species of ducks, nest in the northern United States and -move south for the winter to areas along the Gulf of Mexico. This -list includes the more hardy species, some individuals of which may -linger in protected places well within the reach of severe cold, as, -for example, Wilson's snipe or jacksnipe, which frequently is found -during subzero weather in parts of the Rocky Mountain region where -warm springs assure a food supply. More than 100 of our summer birds -leave the United States entirely and spend the winter in the West -Indies, or in Central America or South America. For example, the -Cape May warbler, which breeds from northern New England, northern -Michigan, and northern Minnesota, north to New Brunswick, Nova -Scotia, and nearly to Great Slave Lake, is concentrated in winter -chiefly in the West Indies, its metropolis at this season being the -island of Hispaniola. - - -=Long-distance migrations= - -Some of the common summer residents are not content with a trip to -northern South America, but push on across the Equator and finally -come to rest for the winter in the pampas of Argentina, or even -in Patagonia. Thus some species that are more or less associated -with each other in summer, as nighthawks, barn swallows, cliff -swallows, and some of the thrushes, may also occupy the same general -winter quarters in Brazil. Some individual nighthawks and barn -swallows travel still farther, and of all North American land birds -these species probably have the longest migration route, as they -occur north in summer to Yukon and Alaska, and south in winter to -Argentina, 7,000 miles away. Such seasonal flights are exceeded in -length, however, by the journeys of several species of water birds, -chiefly members of the suborder of shore birds. In this group there -are 19 species that breed north of the Arctic Circle and winter in -South America, 6 of them going as far south as Patagonia, and thus -having a migration route more than 8,000 miles in length. - -The arctic tern is the champion "globe trotter" and long-distance -flier (fig. 8). Its name "arctic" is well earned, as its breeding -range is circumpolar and it nests as far north as it can find a -suitable place. The first nest to be found in this region was only -7½ degrees from the North Pole, and it contained a downy chick -surrounded by a wall of newly fallen snow that had been scooped -out by the parent. In North America the arctic tern breeds south -in the interior to Great Slave Lake, and on the Atlantic coast to -Massachusetts. After the young are grown the arctic terns disappear -from their North American breeding grounds, and a few months later -they may be found in the Antarctic region, 11,000 miles away. Until -very recently the route followed by these hardy fliers was a complete -mystery, for although a few scattered individuals have been noted -south as far as Long Island, the species is otherwise practically -unknown along the Atlantic coasts of North America and South America. -It is, however, known as a migrant on the west coast of Europe and -Africa. By means of numbered bands the picture is now developing of -what is apparently not only the longest but also one of the most -remarkable of all migratory journeys. - -[Illustration: _Figure 8._--Distribution and migration of the arctic -terns of eastern North America. The route indicated for this bird is -unique, as no other species is known to breed abundantly in North -America and to cross the Atlantic Ocean to and from the Old World. -The extreme summer and winter homes are 11,000 miles apart, and as -the route taken is circuitous, these terns probably fly at least -25,000 miles each year.] - -Judging by the evidence at present available it seems likely that -the arctic terns of eastern North America originally found their way -here from the Old World, probably by way of Iceland and Greenland. -Consequently when the time comes for them to migrate to winter -quarters they do not go directly south as do the common and Forster's -terns, but instead they fly back eastward along their ancestral route -across the Atlantic to the shores of Europe and then go south along -the African coast to their winter home. Those that breed in the -northwestern part of the continent, as in Alaska, probably migrate -chiefly down the western coast, as the species is not infrequently -reported on the coast of California and also on the western coast of -South America. - -The evidence yielded by banding consists of only six definite cases, -but their interpretation permits but one conclusion. All were banded -either as downy chicks or as nonflying immature birds. The details -of their banding and recovery are of sufficient interest to justify -citing in detail. The first was banded on July 3, 1913, at Eastern -Egg Rock, Maine,[2] and in August 1917 was found dead in the Niger -River delta, West Africa. The second was banded at the Red Islands, -Turnevik Bay, Labrador, on July 22, 1927, and was recovered near La -Rochelle, France, on October 1, 1927. The third, also banded on the -Red Islands, on July 23, 1928, was retaken at Margate, near Port -Shepstone, Natal, South Africa, on November 14, 1928. The fourth, -banded at Machias Seal Island, New Brunswick, on July 20, 1935, was -captured near St. Nazaire, France, October 8, 1935. The fifth and -sixth were banded at Machias Seal Island also; the fifth, banded -July 5, 1947, was found on November 10, 1948, at Kingfisher Creek, -Sedgefield, near Wilderness, Eastern Cape Province, South Africa, -while the sixth, banded on July 18, 1948, was picked up dead during -the latter part of September 1948 on the hills near Kyle Strome, -Sutherland, Scotland. All that remained of the bird that provides -the last-named case was a mutilated foot and it appeared that it had -been the victim of some predator. It should be pointed out that the -flights indicated in the third and fifth cases detailed above, are -the longest known for any birds. Both are between 8,000 and 9,000 -miles, which in the case of No. 3 was accomplished in less than 3 -months. - - [2] Recorded at the time of banding as a common tern, a natural - error, as the downy young of common and arctic terns look almost - exactly alike. - -Probably no other animal in the world enjoys as many hours of -daylight as does the arctic tern, since for these birds the sun never -sets during the nesting season in the northern part of the range, -while during their sojourn in the south, daylight is continuous. -During several months of the year they have 24 hours of daylight and -during the other months considerably more daylight than darkness. - - - - - -_Routes of Migration_ - - -While it is beyond question that certain general directions of flight -are constantly followed by migratory birds, it is well to remember -that the term "migration route" is to some extent a theoretical -concept concerned entirely with the lines of general advance or -retreat of a species, rather than the exact course followed by -individual birds. Even the records of banded birds usually show -no more than the place of banding and recovery, and one must -have recourse to intermediate records and to reasoning based on -probabilities to fill in details of the route actually traversed -between the two points. - -There is also infinite variety in the routes covered during migration -by different species. In fact, the choice of migration highways is -so wide that it seems as if the routes of no two species coincide. -Differences in distance traveled, time of starting, speed of flight, -geographical position, latitudes of breeding and of wintering -grounds, and in other factors, all contribute to this great variation -of migration routes. Nevertheless, there are certain factors that -serve to guide the avian travelers along more or less definite lines, -and it is possible to define general lines of migration for the -majority of species. - -It has been frequently observed that migrating birds have a tendency -to follow major topographic lines on the earth's surface when their -trend is in the general direction of the birds' journey. Bird -migration is generally thought of as a north-and-south movement, with -the lanes of heavier concentration following the coasts, mountain -ranges, and principal river valleys. To a considerable extent this -is the case, particularly in North America, where the coast lines, -mountain chains, and larger rivers in general run north and south. -In cases where the migration is a long one, however, the notion must -be abandoned that the birds' flight is always restricted to narrow -routes that follow river valleys and the like, as many species seem -to disregard utterly such apparently good natural highways. For -example, the Arkansas River has a general east-and-west course for a -great part of its length, and while it does constitute a route for -many perching birds en route from the Mississippi Valley to the Rocky -Mountain region, some of the hawks and many ducks and shore birds -pay the valley scant attention. They may arrest the autumn journey -to feed among the cottonwoods or along sand bars, but when ready to -resume their flight they leave the river and fly directly south over -the more or less arid region that lies between the Arkansas and the -Rio Grande. - - -=Wide and narrow migration lanes= - -When birds start their southward migration the movement necessarily -involves the full width of the breeding range. Later there is a -convergence of the lines of flight taken by individual birds, owing -to the conformation of the land mass, and as the species proceeds -southward the width of the occupied region becomes less and less. An -example of this is provided by the common kingbird, which breeds from -Newfoundland to British Columbia, a summer range 2,800 miles wide. On -migration, however, its paths converge until in the southern part of -the United States the occupied area extends from Florida to the mouth -of the Rio Grande, a distance of only 900 miles, and still farther -south the migration path is further restricted. In the latitude of -Yucatan it is not more than 400 miles wide, and it is probable that -the great bulk of the species moves in a belt that is less than half -that width. - -A migration route, therefore, may be anything from a narrow path -that adheres closely to some definite geographical feature, such as -a river valley or a coast line, to a broad boulevard that leads in -the desired direction and which follows only the general trend of the -land mass. Also it is to be remembered that whatever main routes are -described, there remains a multitude of tributary and separate minor -routes. In fact, with the entire continent of North America crossed -by migratory birds, the different groups or species frequently follow -lines that may repeatedly intersect those taken by others of their -own kind or by other species. The arterial routes, therefore, must -be considered merely as indicating paths of migration on which the -tendency to concentrate is particularly noticeable. - -In considering the width of migration lanes it will be obvious that -certain species, as the knot and the purple sandpiper, which are -normally found only along the coasts, must have extremely narrow -routes of travel. They are limited on one side by the broad waters of -the ocean, and on the other by land and fresh water, both of which -are unsuited to furnish the food that is desired and necessary to the -well-being of these species. - -[Illustration: _Figure 9._--Breeding and wintering ranges and -migration of Harris's sparrow, an example of a narrow migration -route through the interior of the country. The heavy broken lines -enclose the region traversed by the majority of these finches; the -light broken line encloses the country where they occur with more or -less regularity; while the spots indicate records of accidental or -sporadic occurrence.] - -Among land birds that have a definite migration, the Ipswich sparrow -has what is probably the most restricted migration range of any -species. It is known to breed only on Sable Island, Nova Scotia, -and it winters along the Atlantic coast south to Georgia. Living -constantly within sound of the surf, it is rarely more than a quarter -of a mile from the outer beach, and is entirely at home among the -sand dunes and their sparse covering of coarse grass. - -[Illustration: _Figure 10._--Distribution and migration of the -scarlet tanager. During the breeding season individual scarlet -tanagers may be 1,900 miles apart in an east-and-west line across the -breeding range. In migration, however, the lines converge until in -southern Central America they are not more than 100 miles apart. For -migration paths of other widths see figures 9, 11, and 12.] - -Harris's sparrow supplies an interesting example of a narrow -migration route in the interior of the country (fig. 9.) This fine, -large finch is known to breed only in the region from Churchill, on -the west shore of Hudson Bay, northwest to the shores of Great Bear -Lake. Very few actual breeding records of the species are available, -but these are sufficient to indicate that the breeding range is in -the strip of country characterized by more or less stunted timber -just south of the limit of trees. When it begins its fall migration, -this species necessarily covers the full width of its breeding area. -Then it proceeds almost directly south, or slightly southeasterly, -the area covered by the majority of the birds becoming gradually -constricted, so that by the time it reaches the United States it is -most numerous in a belt about 500 miles wide, extending across North -Dakota to central Minnesota. Harris's sparrows are noted on migration -with fair regularity east to the western shore of Lake Michigan, and -west to the foothills of the Rocky Mountains, but the great bulk of -the species moves north and south through a relatively narrow path in -the central part of the continent. Present knowledge suggests that -the reason for this narrow migration range is the close association -that Harris's sparrow maintains with a certain type of habitat' -including brushy places, thickets, edges of groves, and weed patches. -While these environmental conditions are found in other parts of -the country, the region crossed by this sparrow presents almost a -continuous succession of habitat of this type. Its winter range -extends from southeastern Nebraska and northwestern Missouri, across -eastern Kansas and Oklahoma and through a narrow section of central -Texas, at places hardly more than 150 miles wide. - -The scarlet tanager presents another extreme case of narrowness of -migration route (fig. 10), its breeding range extending in greatest -width from New Brunswick to Saskatchewan, a distance of about 1,900 -miles. As the birds move southward in fall their path of migration -becomes more and more constricted, until at the time they leave the -United States all are included in the 600-mile belt from eastern -Texas to the Florida peninsula. Continuing to converge through -Honduras and Costa Rica, the boundaries there are not more than 100 -miles apart. The species winters in northwestern South America, where -it spreads out over most of Colombia, Ecuador, and Peru. - -The rose-breasted grosbeak also leaves the United States through -the 600-mile stretch from eastern Texas to Apalachicola Bay, but -thereafter the lines do not further converge, as this grosbeak enters -the northern part of its winter quarters in Central America and South -America through a door of about the same width (fig. 11). - -Although the cases cited represent extremes of convergence, a -narrowing of the migratory path is the rule to a greater or less -degree for the majority of North American birds. The shape of the -continent tends to effect this, and so the width of the migration -route in the latitude of the Gulf of Mexico is usually much less than -in the breeding territory. - -The redstart represents a notable case of a wide migration route, -although even in the southern United States this is much narrower -than the breeding range (fig. 12). These birds, however, cross all -parts of the Gulf of Mexico and pass from Florida to Cuba and Haiti -by way of the Bahamas, so that here their route has a width of about -2,500 miles. - -[Illustration: _Figure 11._--Distribution and migration of the -rose-breasted grosbeak. Though the width of the breeding range is -about 2,500 miles, the migratory lines converge until the boundaries -are only about 700 miles apart when the birds leave the United -States. For migration paths of other widths see figures 9, 10, and -12.] - - -=The flyways= - -In 1935, as a result of studies of banding data, the author -discovered the existence of the four great flyway systems. This -discovery, based upon analyses of the several thousand records of -the recovery of migratory waterfowl then available, was announced by -the Biological Survey (Lincoln, 1935c) and, beginning in 1948, it -has served as the basis for administrative action by the Fish and -Wildlife Service in the annual hunting regulations. - -[Illustration: _Figure 12._--Distribution and migration of the -redstart. An example of a wide migration route, since birds of this -species cross all parts of the Gulf of Mexico, or may travel from -Florida to Cuba and through the Bahamas. Their route thus has an -east-and-west width of more than 2,000 miles. For migration paths of -greater or less extent see figures 9, 10, and 11.] - -Although this study was confined to this one family of birds there -is a growing mass of evidence in support of the belief that all -populations of migratory birds adhere with more or less fidelity to -their respective flyways. The terms "flyway" and "migration route" -have in the past been used more or less as synonyms but the modern -concept of a flyway is that it is a vast geographic region with -extensive breeding grounds and wintering grounds connected with each -other by a more or less complicated system of migration routes. Each -flyway has its own populations of birds, even of those species that -may have a continental distribution. The breeding grounds of one or -more flyways may (and usually do) overlap broadly, so that during the -nesting season extensive areas may be occupied by birds of the same -species but which belong to different flyways. - -The maps (figs. 13, 14, 15, and 16) show the flyways as they are now -understood. It should be pointed out, however, that in the other maps -used in this bulletin, the entire range of a species is shown without -any attempt to distinguish by flyways the different populations. As -banding data accumulate for the nongame species, this distinction -will ultimately be possible, but for the time being, consideration of -their migrations must be chiefly by routes. - -The following discussion of the principal routes of North American -birds relates chiefly to the fall migration, for, except as otherwise -noted, the spring flight generally retraces the same course. The -routes indicated on the map (fig. 17) must not be considered as -representing paths with clearly defined borders, but rather as -convenient subdivisions of the four great flyways that, as indicated -above, cover practically the entire width of the North American -Continent and extend from the Arctic coast to South America. - -[Illustration: _Figure 13._--The Atlantic flyway.] - - -=Atlantic oceanic route= - -By reference to figure 17 it will be noted that route No. 1 is almost -entirely oceanic, passing directly over the Atlantic Ocean from -Labrador and Nova Scotia to the Lesser Antilles, and then through -this group of small islands to the mainland of South America. This -is not a popular route and its chief claim to fame is that it is the -fall route used by most of the adult eastern golden plovers, and -probably by some other shore birds. Since it lies entirely over the -sea, this route is definitely known only at its terminals and from -occasional observations made on Bermuda and other islands in its -course. Some of the shore birds that breed on the Arctic tundra of -Mackenzie and Alaska fly southeastward across Canada to the Atlantic -coast and finally follow this oceanic route to the mainland of South -America. The golden plover may accomplish the whole 2,400 miles -without pause or rest, in fair weather the flocks passing Bermuda and -sometimes even the islands of the Antilles without stopping. Although -most birds make their migratory flights either by day or by night, -the golden plover in this remarkable journey flies both day and -night. As it swims lightly and easily it may make a few short stops -along the way, and it has been seen actually resting on the ocean. -Other shore birds have been observed busily feeding in the great area -of ocean known as the Sargasso Sea, where thousands of square miles -of floating seaweed teem with marine life. - -[Illustration: _Figure 14._--The Mississippi flyway.] - -[Illustration: _Figure 15._--The Central flyway.] - -[Illustration: _Figure 16._--The Pacific flyway.] - -The annual flight of the adult eastern golden plover is so wonderful -that it may be given in some detail, particularly since it is one of -the exceptions to the general rule that spring and fall movements are -over the same routes (fig. 18). After reaching the South American -coast the birds make a short stop and then continue overland to the -pampas of Argentina, where they remain from September to March. -Leaving their winter quarters, they cross northwestern South America -and the Gulf of Mexico, reaching the North American mainland on the -coasts of Texas and Louisiana. Thence they proceed slowly up the -Mississippi Valley, and by the early part of June are again on their -breeding grounds, having performed a round-trip journey in the form -of an enormous ellipse with the minor axis about 2,000 miles and -the major axis 8,000 miles, reaching from the Arctic tundra to the -pampas of Argentina. The older birds are probably accompanied by -some of the young, perhaps those from early nestings, but most of -the immature birds leave their natal grounds late in summer and move -southward through the interior of the country, returning in spring -over essentially the same course. The elliptical route is therefore -used chiefly by fully adult birds. - -[Illustration: _Figure 17._--Principal migration routes used by birds -in passing from North America to winter quarters in the West Indies, -Central America, and South America. Route No. 4 is the one used most -extensively; only a few species make the 2,400-mile flight from Nova -Scotia to South America.] - -[Illustration: _Figure 18._--Distribution and migration of the golden -plover. Adults of the eastern form migrate across northeastern -Canada and then by a nonstop flight reach South America. In spring -they return by way of the Mississippi Valley. Their entire route is -therefore in the form of a great ellipse with a major axis of 8,000 -miles and a minor axis of about 2,000 miles. The Pacific golden -plover, which breeds in Alaska, apparently makes a nonstop flight -across the ocean to Hawaii, the Marquesas Islands, and the Low -Archipelago, returning in spring over the same route.] - - -=Atlantic coast route and tributaries= - -The Atlantic coast is a regular avenue of travel, and along it are -many famous points for observing both land and water birds. About 50 -different kinds of land birds that breed in New England follow the -coast southward to Florida and travel thence by island and mainland -to South America (fig. 17, route 2). As will be seen from the map, a -seemingly natural and convenient highway extends through the Bahamas, -Cuba, Hispaniola, Puerto Rico, and the Lesser Antilles to the South -American coast. Resting places are afforded at convenient intervals, -and at no time need the aerial travelers be out of sight of land. It -is not, however, the favored highway, and only about 25 species of -birds go beyond Cuba to Puerto Rico along this route to their winter -quarters, while only 6 species are known to reach South America by -way of the Lesser Antilles. The obvious draw-back is lack of adequate -food. The total area of all the West Indies east of Puerto Rico is -less than that of Rhode Island, so that if only a small part of -the birds of the eastern United States were to travel this way, it -is doubtful whether even the luxuriant flora and fauna of tropical -habitats would provide food sufficient for their needs. Nevertheless, -many thousands of coots, widgeons, pintails, blue-winged teal, and -other waterfowl and shorebirds regularly spend the winter season -in the coastal marshes and the inland lakes and ponds of Cuba, -Hispaniola, and Puerto Rico. - -The map (fig. 17) also will show that route No. 3 presents a direct -line of travel for Atlantic coast migrants en route to South America, -although it involves much longer flights. It is used almost entirely -by land birds. After taking off from the coast of Florida there are -only two intermediate land masses where the migrants may pause for -rest and food. Nevertheless, tens of thousands of birds of some 60 -species cross the 150 miles from Florida to Cuba where about half -this number elect to remain for the winter months. The others do not -hesitate to fly the 90 miles between Cuba and Jamaica, but from that -point to the South American coast there is a stretch of islandless -ocean fully 500 miles across. Scarcely a third of the North American -migrants leave the forested mountains of Jamaica to risk the perils -of this ocean trip. Chief among these is the bobolink, which so far -outnumbers all other birds using this route that it may be well -called the "bobolink route" (fig. 19). As traveling companions -along this route, the bobolink may meet a vireo, a kingbird, and a -nighthawk from Florida; the chuck-wills-widow of the Southeastern -States; the black-billed and the yellow-billed cuckoos from New -England; the gray-cheeked thrush from Quebec; bank swallows from -Labrador; and the blackpolled warbler from Alaska. Sometimes this -scattered assemblage will be joined by a tanager or a wood thrush -but the "bobolink route" is not popular with the greater number of -migrants, and although many individuals traverse it, they are only a -small fraction of the multitudes of North American birds that spend -the winter in South America. - -[Illustration: _Figure 19._--Distribution and migration of the -bobolink. In crossing to South America most of the bobolinks use -route 3 (fig. 17), showing no hesitation in making the flight from -Jamaica across an islandless stretch of ocean. It will be noted that -colonies of these birds have established themselves in western areas, -but in migration they adhere to the ancestral flyways and show no -tendency to take the short cut across Arizona, New Mexico, and Texas. -(See p. 55.)] - -Formerly it was thought that most of the North American land birds -that migrate to Central America made a leisurely trip along the -Florida coast, crossed to Cuba, and thence made the short flight -from the western tip of Cuba to Yucatan. A glance at the map would -suggest this as a most natural route, but as a matter of fact it is -practically deserted except for a few swallows and shorebirds, or an -occasional land bird storm-driven from its accustomed course. What -actually happens is that in the fall many of the birds that breed -east of the Allegheny Mountains travel parallel to the seacoast in -a more or less southwesterly direction and, apparently maintaining -this same general course from northwestern Florida, cross the Gulf of -Mexico to the coastal regions of eastern Mexico. - -The routes used by the Atlantic brant merit some detail for the -reason that these were long misunderstood. These birds winter on -the Atlantic coast, chiefly at Barnegat Bay, N. J., but (depending -upon the severity of the season and the food available) south also -to North Carolina. Their breeding grounds are in the Canadian arctic -archipelago and on the coasts of Greenland. According to the careful -studies of Lewis (1937), the main body travels northward in spring -along the coast to the Bay of Fundy, hence overland to Northumberland -Strait, which separates Prince Edward Island from the mainland of New -Brunswick and Nova Scotia. A minor route appears to lead northward -from Long Island Sound by way of such valleys as those of the -Housatonic and Connecticut Rivers, and on across southern Quebec to -the St. Lawrence River. - -After spending the entire month of May feeding and resting in various -parts of the Gulf of St. Lawrence, the eastern segment of the brant -population suddenly resumes its journey by crossing to the north -shore of the St. Lawrence estuary. The Bay of Seven Islands, in this -general region, is the point of departure for long overland flights -that are made by the two segments of the population. The eastern -and larger of these appears to fly almost due north to Ungava Bay -and from there to nesting grounds, probably in Baffin Island and -Greenland. The smaller segment travels a route that is but slightly -north of west to the southeastern shores of James Bay, although -somewhere to the east of that area some of the flocks take a more -northwesterly course, descending the Fort George River to reach the -eastern shore of James Bay about two-thirds of the distance north of -its southern extremity. Upon their arrival at either of these two -points on James Bay, the brant of this western segment turn northward -and proceed through the eastern part of Hudson Bay to their breeding -grounds, probably in western Baffin Island, Southampton Island, and -other islands in the Canadian Arctic. - -In general, the fall migration of the brant follows the routes -utilized in the spring. At this season, when gathering for the -flight of 570 miles to the St. Lawrence River, they appear only on -the western and southern shores of Ungava Bay. Also, it appears that -most of the birds of the western segment, instead of following the -eastern shores of Hudson and James Bays, turn southwestward across -the former, by way of the Belcher Islands, to Cape Henrietta Maria -and from there south along the western shores of James Bay by way of -Akimiski and Charlton Islands. At the southern end of James Bay they -are joined by those that have taken the more direct route along the -east coasts of the bays and all then fly overland 570 miles to the -estuary of the St. Lawrence River. - -The Atlantic flyway receives accretions of waterfowl from three or -four interior migration paths, one of which is of first importance, -as it includes great flocks of canvasbacks, redheads, scaup ducks, -Canada geese, and many of the black ducks that winter in the waters -and marshes of the coastal region south of Delaware Bay. The -canvasbacks, redheads, and scaups come from their breeding grounds -on the great northern plains of central Canada, follow the general -southeasterly trend of the Great Lakes, cross Pennsylvania over -the mountains, and reach the Atlantic coast in the vicinity of -Delaware and Chesapeake Bays. Black ducks, mallards, and blue-winged -teals that have gathered in southern Ontario during the fall leave -these feeding grounds and proceed southwest over a course that is -apparently headed for the Mississippi Valley. Many do continue this -route down the Ohio Valley, but others, upon reaching the vicinity -of the St. Clair Flats, between Michigan and Ontario, swing abruptly -to the southeast and, crossing the mountains in a single flight, -reach the Atlantic coast south of New Jersey. This route, with -its Mississippi Valley branch, has been fully demonstrated by the -recovery records of ducks banded at Lake Scugog, Ontario. - -The white-winged scoter, which also breeds in the interior of the -continent from northern North Dakota north to the Arctic coast, was -at one time credited with an elliptical migration route, at least -insofar as those wintering on the Atlantic coast are concerned. -This sea duck nests only near fresh water but spends the winters on -the ocean along both the Atlantic and Pacific coasts of the United -States. It migrates over land surfaces mainly at night and it is now -believed that after working northward to the waters of Long Island -Sound it starts up the valleys of the Hudson and Connecticut Rivers -and flies overland to the Great Lakes, from which region it continues -west and northwest to the breeding grounds, returning to its winter -quarters over the same route. Early ideas alleging an elliptical -route probably arose from the fact that great numbers of first-year -nonbreeding birds regularly pass up the New England coast, cross the -Gulf of St. Lawrence and spend the summer loafing off the coast of -Labrador. In the fall these birds form into large flocks and retrace -their flight, chiefly during daylight hours, to winter quarters from -southeastern Maine south at least to Chesapeake Bay. As it was not -known that the white-winged scoter does not usually breed until it is -2 years old, and since the southward movement of yearling birds was -conspicuous while the travels of those from the nesting grounds were -chiefly at night, the theory was advanced that the latter flew 1,500 -miles due east from the region west of Hudson Bay to the coast of -Labrador, thence southward to the known winter quarters. - -A study of the Canada geese that winter abundantly in the waters of -Back Bay, Va., and Currituck Sound, N. C., reveals another important -tributary to the Atlantic coast route. Banding has shown that the -principal breeding grounds of these birds are among the islands -and on the eastern shore of Hudson Bay. From this region they move -south in autumn to the point of Lower Ontario between Lakes Erie -and Huron. Occasionally one of these geese will be recovered in the -Mississippi Valley but the great majority are retaken either on their -breeding grounds or on the Atlantic coast south of Delaware Bay, -showing another instance of a long cross-country flight by waterfowl. -Although the Canada goose is abundant in migration on the coast of -New England, the birds taken there rarely include any of those banded -in southern Ontario. The northeastern population of these geese comes -from breeding areas in New England, the Maritime Provinces of Canada, -Newfoundland, and the desolate coast of Labrador, their migration -being entirely coastwise. Still another cross-country route between -the Mississippi Valley and the Atlantic coast remains to be briefly -described. It is not yet well understood, but the banding of ducks -such as the blue-winged teal on the coastal saw-grass marshes of -South Carolina has revealed that there is a migration route across -the Appalachians to the Mississippi Valley. Birds marked in these -marshes have been retaken in Tennessee and Kentucky, as well as in -other States farther north in the Mississippi Flyway. - - -=Mackenzie Valley--Great Lakes--Mississippi Valley route and -tributaries= - -Easily the longest route of any in the Western Hemisphere is that -extending from the Mackenzie Valley past the Great Lakes and down the -Mississippi River, including its tributaries. Its northern terminus -is on the Arctic coast in the regions of Kotzebue Sound, Alaska, -and the mouth of the Mackenzie River, while its southern end lies -in Patagonia. During the spring migration some of the shore birds -traverse the full extent of this great path, and it seems likely -that the nighthawk, the barn swallow, the blackpolled warbler, and -individuals of several other species that breed north to Yukon and -Alaska must twice each year cover the larger part of it. - -For more than 3,000 miles--from the mouth of the Mackenzie to the -delta of the Mississippi--this route is uninterrupted by mountains. -In fact, there is not even a ridge of hills high enough to interfere -with the movements of the feathered travelers, and the greatest -elevation above sea level is less than 2,000 feet. Well timbered and -watered, the entire region affords ideal conditions for the support -of its great hosts of migrating birds. It is followed by such vast -numbers of ducks, geese, shore birds, blackbirds, sparrows, warblers, -and thrushes, that observers stationed at favorable points in the -Mississippi Valley daring the height of migration can see a greater -number of species and individuals than can be noted anywhere else in -the world. - -Starting in the region of Kotzebue Sound, Alaska, the route extends -eastward across northern Alaska and joins another that has its origin -at the mouth of the Mackenzie River. The line of flight then trends a -little east of south through the great lake system of central Canada, -where it is joined by two or three other routes from the northeast -that have their origin on the central Arctic coast. Continuing -southward the migrating flocks are constantly augmented by additions -to their numbers as they pass over the great breeding grounds of -central and southern Canada. Upon reaching the headwaters of the -Missouri and Mississippi Rivers the route follows these streams to -the Gulf coast, Arriving in this latitude many species, including -the ducks and geese, the robin, the myrtle warbler, and some others -spread out east and west for their winter sojourn. Others, despite -the perils of a trip involving a flight of several hundred miles -across the Gulf of Mexico, strike out boldly for Central America -and South America. This part of the route is a broad "boulevard" -extending from northwestern Florida to eastern Texas and reaching -southward across the Gulf of Mexico to Yucatan and the Isthmus of -Tehuantepec (fig. 17, route 4). In other words, when most of the -birds (chiefly shore birds and land birds) that have come south -directly through the Mississippi Valley have reached the coastal -plains of Mississippi and Louisiana, they continue directly across -the Gulf of Mexico. This route appears to have preference over the -safer but more circuitous land or island routes by way of Texas and -Florida. During the height of migration some of the islands off the -coast of Louisiana are wonderful observation points for the student -of birds, as the feathered travelers literally swarm over them. - -Present detailed knowledge of the chief tributaries to the -Mackenzie--Great Lakes--Mississippi Valley highway relates chiefly -to waterfowl. Reference already has been made to the flight of the -black ducks (p. 58) that reach the Mississippi Valley from southern -Ontario. Some individuals of this species banded at Lake Scugog, -Ontario, have been recaptured in succeeding seasons in Wisconsin -and Manitoba, but the majority have been retaken at points south -of the junction of the Ohio River with the Mississippi, definitely -indicating their route of travel from southern Ontario. - -A second route that joins the main artery on its eastern side is -the one used by the blue goose, the migration route of which is -probably more nearly due north and south than that of any other -North American bird. The breeding grounds, which only in recent -years have been discovered, are mainly in the Fox Basin region of -Baffin Island and on Southampton Island. In fall these geese work -southward, chiefly along the eastern shore of Hudson Bay, and upon -reaching the southern extremity of James Bay they take off for what -is practically a nonstop flight to the great coastal marshes of -Louisiana west of the delta of the Mississippi River. In some seasons -the flocks make intermediate stops among the islands and sand bars -of the Mississippi, as they are occasionally common in the general -vicinity of Memphis, Tenn. Most of the birds push on, however, and -during the period from the first of November to the last of March -fully 90 percent of the species are concentrated in the area between -the Sabine and the Mississippi Rivers. On the return trip northward -there is sometimes a tendency for some of the blue geese to veer off -toward the northwest, as they are occasionally abundant in eastern -South Dakota and southeastern Manitoba. It is of particular interest -to note that while some other geese and many ducks start their -northward journey at the first sign of awakening spring, the blue -goose remains in its winter quarters until the season there is far -advanced, seemingly aware that its own breeding grounds in the Arctic -are still in the grip of winter. - - -=Great Plains--Rocky Mountain routes= - -A great western highway also has its origin in the Mackenzie River -delta area and in Alaska. This is used chiefly by the pintail and the -American widgeon or baldpate, which fly southward through eastern -Alberta to western Montana. Some localities in this area, as for -example, the National Bison Range at Moiese, Mont., normally furnish -food in such abundance as to induce these birds to pause in their -migratory movement. Upon resuming travel, some flocks move almost -directly west across Idaho to the valley of the Columbia River, from -which they turn abruptly south to the interior valleys of California. -Others leave the Montana feeding and resting areas and turn -southeastward across Wyoming and Colorado to join the flocks that are -moving southward through the Great Plains (fig. 15). - -Many redheads that breed in the Bear River marshes in Utah take a -westerly route across Nevada to California, but some leave these -breeding grounds and fly northeastward across North Dakota and -Minnesota to join the flocks of these ducks that come out of the -prairie regions of Canada. A few of them even travel southeastward to -the Atlantic coast. This route can be traced by the records of ducks -banded in summer in the Bear River marshes and retaken the following -fall at points in eastern Montana, Wyoming, South Dakota, North -Dakota, Minnesota, Wisconsin, Michigan, Ohio, and Maryland. Great -numbers, however, follow another route from these marshes across the -mountains in an easterly direction, where it almost immediately turns -southward through Colorado and New Mexico, and continues to winter -quarters in the Laguna Madre off the coast of Texas or in the Valley -of Mexico (fig. 17, route 6). This route also represents the travels -of many of the land birds of the Rocky Mountain region. Such birds -perform comparatively short migrations, most of them being content -to stop when they reach the middle districts of Mexico, only a few -passing beyond the southern part of that country. - -Observations made in the vicinity of Corpus Christi, Tex., have -shown one of the short cuts (fig. 17, route 5) that is, in effect, -a part of the great artery of migration. Thousands of birds pass -along the coast to the northern part of the State of Vera Cruz. As -the coast of the State of Tamaulipas to the north is arid and so -entirely unsuited to the needs of birds that are frequenters of moist -woodlands, it is probable that much or all of this part of the route -is a short distance off shore. It is used by such woodland species as -the golden-winged warbler, the worm-eating warbler, and the Kentucky -warbler. - - -=Pacific coast route= - -Although it does present features of unusual interest, the Pacific -coast route is not of so great importance as some of the others -described. Because of the equable conditions that prevail, many -species of birds along the coast from the Northwestern States to -southeastern Alaska either do not migrate at all or else make -relatively short journeys. This route has its origin chiefly in -Alaska, the general region of the delta of the Yukon River marking -its northern terminus, although a few species join it after a flight -westward along the Alaskan Arctic coast. Some of the scoters and -other sea ducks of the north Pacific region, and the diminutive -cackling goose which breeds in the delta of the Yukon River, use the -coastal sea route for all or most of their southward flight. The -journey of the cackling goose, as shown by return records from birds -banded at Hooper Bay, Alaska, has been traced southward across the -Alaska Peninsula and apparently across the Gulf of Alaska to the -Queen Charlotte Islands, the birds following the coast line south -to near the mouth of the Columbia River. There the route swings -toward the interior for a short distance before continuing south -by way of the Willamette River Valley. The winter quarters of the -cackling goose are chiefly in the vicinity of Tule Lake, on the -Oregon-California line, and in the Sacramento Valley of California, -though a few push on to the San Joaquin Valley. - -[Illustration: _Figure 20._--The breeding range, winter range, and -migration route of Ross's goose. This is the only species of which -all members apparently breed in the Arctic regions, migrate south -through the Mackenzie Valley, and upon reaching the United States, -turn to the southwest rather than the southeast. The southern part -of this route, however, is followed by some mallards, pintails, -baldpates, and possibly by other ducks.] - -A tributary of this flyway is followed by Ross's goose which is now -known to breed only in the Perry River district south of the Queen -Maud Gulf on the central Arctic coast of Canada (fig. 20). Its fall -migration appears to be southwest and south across the barren grounds -to Great Slave and Athabaska Lakes, where it joins thousands of other -waterfowl bound for their winter homes along the eastern coast of the -United States and the Gulf of Mexico. But when the Ross's geese have -traveled south approximately to the northern boundary of Montana, -they separate from their companions, and turning to the southwest -cross the Rocky Mountains and settle for the winter in California. - -[Illustration: _Figure 21._--Breeding and wintering ranges of the -western tanager. See figure 22 for the spring route taken by the -birds breeding in the northern part of the range.] - -The route taken by the white-winged scoters that winter on the -Atlantic coast already has been indicated (p. 59). Some birds of this -species, however, winter on the Pacific coast from Puget Sound south -to southern California. Their passage by thousands up and down the -coast has been noted as far north as northwestern British Columbia. -The species is known to nest in Alaska, which may be the home of -some, at least, of the scoters that winter on the Pacific coast. If -such be the case, however, it must be admitted that a part of the -route taken by the birds when on migration is unknown, though very -few observations are available from the interior of northern British -Columbia, across which the route may lie. - -The southward route of those migratory land birds of the Pacific -coast that in winter leave the United States extends chiefly through -the interior of California to the mouth of the Colorado River and on -to winter quarters in western Mexico. - -The movements of the western tanager show a migration route that is -in some ways remarkable. The species breeds in the mountains from -the northern part of Baja California and western Texas north to -northeastern British Columbia and southwestern Mackenzie. Its winter -range is in two discontinuous areas--southern Baja California and -eastern Mexico south to Guatemala (fig. 21). On the spring migration -the birds enter the United States about April 20, appearing first in -western Texas and the southern parts of New Mexico and Arizona (fig. -22). By April 30 the vanguard has advanced evenly to an approximate -east-and-west line across central New Mexico, Arizona, and southern -California. But by May 10 the easternmost birds have advanced only to -southern Colorado, while those in the far west have reached northern -Washington. Ten days later the northward advance of the species is -shown as a great curve, extending northeastward from Vancouver Island -to central Albert and thence southeastward to northern Colorado. -Since these tanagers do not reach northern Colorado until May 20, -it is evident that those present in Alberta on that date, instead -of traveling northward through the Rocky Mountains, which from the -location of their summer and winter homes would seem to be the -natural route, reached there by the Pacific coast route to southern -British Columbia and thence across the mountains, despite the fact -that these are still partly covered with snow at that time. - - -=Pacific oceanic route= - -The route of the Pacific golden plover is fully as interesting and as -remarkable as the elliptical course followed by its eastern cousin -(fig. 18). The breeding range of the eastern golden plover extends -through Arctic America west to the northern coast of Alaska where, -in the vicinity of Point Barrow, it meets the nesting grounds of -the Pacific form, which is really an Asiatic subspecies. It breeds -chiefly in the Arctic coast region of Siberia and merely overflows -onto the Alaskan coast, some of the birds probably migrating south -along the coast of Asia to winter quarters in Japan, China, India, -Australia, New Zealand, and Oceania, including the Hawaiian Islands, -the Marquesas Islands, and the Low Archipelago. Golden plovers in -migration have been observed at sea on a line that apparently extends -from these islands to the Aleutians, and it therefore appears certain -that at least some of the Alaskan birds make a nonstop flight across -a landless sea from Alaska to Hawaii. While it would seem incredible -that any birds could lay a course so straight as to attain these -small oceanic islands, 2,000 miles south of the Aleutians, 2,000 -miles west of Baja California, and nearly 4,000 miles east of Japan, -the evidence admits only the conclusion that year after year this -transoceanic round-trip journey between Alaska and Hawaii is made by -considerable numbers of golden plovers. - -[Illustration: _Figure 22._--Migration of the western tanager. -The birds that arrive in eastern Alberta by May 20 do not travel -northward along the eastern base of the Rocky Mountains, as in that -region the van has then only reached northern Colorado. Instead the -isochronal lines indicate that they migrate north through California, -Oregon, and Washington, and then cross the mountains of British -Columbia.] - -The Pacific oceanic route probably is used also by the arctic terns -that breed in Alaska, and possibly by those from the more western -tern colonies of Canada. This species is of regular occurrence on -the western coasts of both the United States and South America, -indicating that the western representatives travel southward to the -Antarctic winter quarters without the spectacular migration features -that appear to characterize the flight of those from the eastern part -of the continent (fig. 8). - - -=Arctic routes= - -In the discussion of the migration of the Arctic tern (p. 38) it was -noted that this species makes a very distinct west-to-east movement -across northern Canada, continuing the flight eastward across the -Atlantic Ocean toward the western coast of Europe. It seems likely -that there are other species, including the parasitic jaeger, that -regularly breed in the northern part of the Western Hemisphere but -migrate back to the Old World for their winter sojourn. Some others, -as the red-legged kittiwake and Ross's gull, remain near the Arctic -region throughout the year, retreating southward in winter only a few -hundred miles. The emperor goose in winter is found only a relatively -short distance south of its breeding grounds, and eider ducks, -although wintering in latitudes well south of their nesting areas, -nevertheless remain farther north than do the majority of other -species of ducks. - -The routes followed by these birds are chiefly coastwise, and in the -final analysis may be considered as being tributary either to the -Atlantic or to the Pacific coast routes. The passage of gulls, ducks, -the black brant, and other water birds at Point Barrow, Alaska, -and at other points on the Arctic coast, has been noted by several -observers, and from present knowledge it may be said that the best -defined Arctic route in North America is the one that follows around -the coast of Alaska. - -[Illustration: _Figure 23._--Distribution and migration of the -red-eyed vireo. It is evident that the red-eyed vireo has only -recently invaded Washington by an extension of its breeding range -almost due west from the upper Missouri Valley. Like the bobolink, -however (fig. 19), the western breeders do not take the short cut -south or southeast from their nesting grounds, but migrate spring and -fall along the route traveled in making this extension.] - - - - -_Evolution of Migration Routes_ - - -From the foregoing descriptions of migration routes it will be -observed that the general trend of migration in most species of North -American birds is northwest and southeast. It is comparatively easy -to trace the probable steps in the evolution of the migrations of -some species, and some routes have developed so recently that they -still plainly show their origin. - -The tendency is for eastern species to extend their ranges by pushing -westward, particularly in the north. For example, in the Stikine -River Valley of northern British Columbia and southwestern Alaska the -eastern nighthawk, eastern chipping sparrow, rusty blackbird, eastern -yellow warbler, redstart, and others have established breeding -stations at points 20 to 100 miles from the Pacific Ocean. The robin, -flicker, slate-colored junco, blackpolled and myrtle warblers, -and ovenbird, all common eastern species, also are established as -breeding birds in western Alaska, the ovenbird having been detected -on the lower Yukon River. These birds are essentially Atlantic and -Mississippi Flyway species, however, and so do not migrate in fall -by any of the Pacific or Central routes, but instead retrace their -journey across the mountains and move southward along the broad -flyways of the East. - -The red-eyed vireo, a striking example of an abundant woodland bird, -is essentially an inhabitant of States east of the Great Plains, but -an arm of its breeding range extends northwest to the Pacific coast -in British Columbia (fig. 23). It seems evident that this is a range -extension that has taken place comparatively recently by a westward -movement from the upper Missouri Valley, and that the invaders -retrace in spring and fall the general route by which they originally -entered the country. - -In the case of the bobolink, a new extension of the breeding range, -and a consequent change in the migration of the species, has taken -place since the settlement of the country (fig. 19). A bird of damp -meadows, it was originally cut off from the Western States by the -intervening arid regions. But with the advent of irrigation and the -bringing of large areas under cultivation, small colonies of nesting -bobolinks have appeared at various western points, and now the -species is established as a regular breeder in the great mountain -parks and irrigated valleys of Colorado and elsewhere almost to the -Pacific coast. In retracing their course to reach the western edge -of the route followed by the bulk of the bobolinks that breed in the -northern United States and southern Canada, these western pioneers -must fly long distances along a line that runs almost due east and -west. - -Similarly it is possible to sketch what seems to be the logical -evolution of the remarkable routes of the golden plover (fig. 18). It -may be assumed that the eastern birds of this species first followed -an all-land route from the South American winter quarters through -Central America, Mexico, and Texas to the western parts of the -Mississippi Valley. As the migration route lengthened northward with -the retreat of the ice and the bird's powers of flight developed, -there would be a tendency to straighten the line and to shorten it -by cutting off some of the great curve through Mexico and Texas. -First a short flight across the western part of the Gulf of Mexico -was probably essayed. Proving successful, this was followed by flight -lines that moved farther east, until finally the roundabout curve -through Texas was entirely discarded and the flight made directly -across the Gulf to southern Louisiana. - -As the great areas in Canada were gradually added to the birds' -domain, other important factors arose, the chief being the -attractiveness of the vast stretches of coast and plain of the -Labrador Peninsula, which in fall offered a bountiful store of -berries. The fall route therefore worked eastward to the Gulf of -St. Lawrence, thence southwest along the coast to Florida and -across the Gulf of Mexico to the Central American mainland. A -series of shortening flights followed to take out the great curve -of the Atlantic coast. A relatively short ocean flight was probably -attempted, say from Cape Cod to the Bahama Islands, Cuba, and -Jamaica, followed eventually by the long direct oceanic route as it -is now known. - -As the Labrador Peninsula in spring is bound by frost and shrouded -in fog while the season advances rapidly through the interior, the -oceanic route proved useful only in fall, and the spring flight -continued through the Mississippi Valley. This outline, although -entirely hypothetical, gives a probable and fairly plausible -explanation of the origin of this wonderful route, particularly -when it is remembered that migration routes as now known are -evolutions--age-long modifications of other routes. - -The evolution of the migration route of the Pacific golden plover -may be explained in a similar fashion. At first the route probably -followed the Asiatic coast, through the Malay Peninsula and Oceania, -thence east in a great curve to the Low Archipelago, with individuals -and flocks dropping out to winter at many points along the way. The -Siberian birds probably continue to follow this ancient highway, but -those nesting in Alaska began a long evolutionary series of flights -that cut down the length of their journey by shortening the curve, -until finally the transoceanic route of the present day was developed. - -This theory of the evolution of migration routes has been questioned -by some ornithologists on the ground that it implies the possession -in some degree of reasoning powers such as would be used by human -beings. This opposition suggests that changes in migration routes -might develop suddenly following mass survival of birds that were -driven over the new route by a storm on some specific occasion. -In the language of genetics, the new route would be, in effect, a -mutation, rather than the result of an accumulation of infinitesimal -variations. There is some evidence in support of this opposing -theory. For example, information from the Hudson's Bay Co. post at -Great Whale River, on the southeastern coast of Hudson Bay, indicates -that in 1884 the snow geese suddenly changed their route from the -eastern to the western coasts of Hudson and James Bays. According to -one report, this change was caused by strong winds from the south -which caught the birds in their fall migration and caused them to -cross the entrance of James Bay from Cape Jones to the western -side; the route thus reportedly forced upon them was then used in -succeeding years. - - - - -_Vertical Migration_ - - -In the effort to find winter quarters furnishing satisfactory living -conditions, many North American birds fly hundreds of miles across -land and sea. Others, however, are able to attain their objective -merely by moving down the sides of a mountain. In such cases a few -hundred feet of altitude correspond to hundreds of miles of latitude. -Movements of this kind, known as "vertical migrations," are found -wherever there are large mountain ranges. In the Rocky Mountain -region they are particularly notable, as chickadees, rosy finches, -juncos, pine grosbeaks, and some other species that nest in the -Alpine Zone move down to the lower levels to spend the winter. It -has been noted that such species as Williamson's sapsucker and the -western wood pewee, which nest in the higher mountains, move down -to the lower regions in August following the breeding season. There -is a distinct tendency among the young of mountain-breeding birds to -work down to the lower levels as soon as the nesting season is over. -The sudden increases among birds in the edges of the foothills are -particularly noticeable when cold spells with snow or frost occur at -the higher altitudes. - -Some species that normally breed in the Hudsonian or Arctic Zones -find suitable breeding areas on the higher levels of the mountains, -as for example the pipit, or titlark, which breeds on the tundra of -Alaska and northern Canada and also south as far as Colorado on the -summits of many peaks in the Rocky Mountains. On the other hand, a -few species, as the Clark's crow, or nutcracker, nest at relatively -low altitudes in the mountains and as the summer advances move -higher up, thus performing a vertical migration that in a sense is -comparable with the post-breeding movements of herons on the Atlantic -coast. These illustrations show that the length of a migration route -may depend upon factors other than latitude. - - - - -_Vagrant Migration_ - - -The most striking feature of the migrations of some of the herons -is a northward movement after the nesting season. The young of some -species commonly wander late in the summer and in fall, sometimes -traveling several hundred miles north of the district in which they -were hatched. The little blue heron breeds commonly north to South -Carolina, and by the last of July the young birds begin to appear -along the Potomac, Patuxent, and Susquehanna Rivers, tributary to -Chesapeake Bay. Although almost all are immature individuals, as -shown by their white plumage, an occasional adult may be noted. With -them come egrets and snowy herons and on occasion all three species -will travel in the East as far north as New England, and in the -Mississippi Valley to southeastern Kansas and Illinois. In September -most of them disappear, probably returning south by the same route. - -The black-crowned night heron has similar wandering habits, and -young birds banded in a large colony at Barnstable, Mass., have -been recaptured the same season north to Maine and Quebec and west -to New York. This habit seems to be shared by some of the gulls -also, although here the evidence is not so conclusive. Herring gulls -banded as chicks at colonies in the Great Lakes have scattered in -all directions after the breeding season, some having been recovered -well north in Canada. - -These movements may be considered as migration governed only by -the availability of food, and they are counteracted in fall by a -directive migratory impulse that carries back to their normal winter -homes in the south those birds that after the nesting period attained -more northern latitudes. They are not to be compared with the great -invasions of certain birds from the North. Classic examples of the -latter in the eastern part of the country are the periodic flights of -crossbills. Sometimes these migrations will extend well south into -the Carolinian Zone. - -Snowy owls are noted for occasional invasions that have been -correlated with the periodic maximum of Arctic foxes and the lemming -cycle in the north. According to Gross (1947) 24 major invasions -occurred between 1833 and 1945. The interval between these varied -from 2 to 14 years, but nearly half (11) were at intervals of 4 -years. A great flight occurred in the winter of 1926-27 when more -than 1,000 records were received from New England alone, but the -largest on record was in 1945-46 when the "Snowy Owl Committee" -of the American Ornithologists' Union received reports of 13,502 -birds, of which 4,443 were reported as killed. It extended over the -entire width of the continent from Washington and British Columbia -to the Atlantic coast and south to Nebraska, Illinois, Indiana, -Pennsylvania, and Maryland. One was taken as far south as South -Carolina. - -In the Rocky Mountain region great flights of the beautiful Bohemian -waxwing are occasionally recorded. The greatest invasion in the -history of Colorado ornithology occurred in February 1917, at which -time the writer estimated that at least 10,000 were within the -corporate limits of the city of Denver. The last previous occurrence -of the species in large numbers in that section was in 1908. - -Evening grosbeaks likewise are given to performing more or less -wandering journeys, and curiously enough, in addition to occasional -trips south of their regular range, they travel east and west, -sometimes covering long distances. For example, grosbeaks banded at -Sault Ste. Marie, Mich., have been recaptured on Cape Cod, Mass., and -in the following season have been retrapped at the banding station. -Banding records demonstrate that this east-and-west trip across the -northeastern part of the country is sometimes made also by purple -finches. - - - - -_Perils of Migration_ - - -The period of migration is a season full of peril for birds. Untold -thousands of the smaller migrants are destroyed each year by storms -and through attacks of predatory birds, mammals, and reptiles. If -each pair of adult birds should succeed in raising two fledglings to -maturity, the population of migratory birds would have a potential -annual increase of 100 percent and the world would soon be heavily -overpopulated with them. Since there is no such increase it is -evident that the annual mortality from natural causes is heavy enough -to keep it in check. - - -=Storms= - -Of the various factors limiting the abundance of birds, particularly -the smaller species, storms are the most potent. Special sufferers -are those birds that in crossing broad stretches of water are forced -down by a storm within reach of the waves. Such a catastrophe was -once seen from the deck of a vessel in the Gulf of Mexico, 30 miles -off the mouth of the Mississippi River. Great numbers of migrating -birds, chiefly warblers, had accomplished nearly 95 percent of -their long flight and were nearing land, when, caught by a norther -against which they were unable to contend, hundreds were forced into -the waters of the Gulf and drowned. On another occasion, on Lake -Michigan, a severe storm came up at a time when large numbers of -migratory birds were crossing and forced numerous victims into the -waves. During the fall migration of 1906, when thousands of birds -were crossing Lake Huron, a sudden drop in temperature accompanied -by a heavy snowfall resulted in the death of incredible numbers. -Literally thousands were forced into the water and subsequently cast -up along the beaches, where in places their bodies were piled in -windrows. On one section of the beach the dead birds were estimated -at 1,000 per mile, and at another point at 5 times that number. Most -of them were species that rank among our most desirable birds as -destroyers of insects and weed seeds, including slate-colored juncos, -tree sparrows, white-throated sparrows, swamp sparrows, winter wrens, -and golden-crowned kinglets, together with many brown creepers, -hermit thrushes, warblers, vireos, and others. - -Of all species of North American birds, the Lapland longspur seems to -be the most frequent victim of mass destruction from storms. These -birds sometimes congregate in enormous numbers where grass or weed -seed is abundant. Almost every winter brings in reports of their -death by thousands somewhere in the Middle West. While migrating -northward at night they have encountered blinding storms of wet, -clinging snow, which have so bewildered them that they have flown -into various obstructions, or have sunk to the ground and perished -of exposure and exhaustion. In 1907 an experienced ornithologist -estimated that 750,000 longspurs were lying dead on the ice of 2 -lakes in Minnesota, each about 1 square mile in extent, and dead -birds were reported in greater or less abundance on this occasion -over an area of more than 1,500 square miles. The heaviest mortality -occurred in towns, where, bewildered by the darkness and the heavy -falling snow, some of the birds congregating in great numbers flew -against various obstacles and were killed or stunned, while many -others fell to the ground exhausted. Similar catastrophes have been -reported from eastern Colorado, Nebraska, and North Dakota. - -During the early part of June 1927, a hailstorm of exceptional -severity in and around Denver, Colo., killed large numbers of robins, -meadow larks, sparrows, and others. The lawns of parks were strewn -with the bodies of these birds, and many lay dead in their nests -where they were covering their eggs or young when the storm broke. - - -=Aerial obstructions= - -Lighthouses, lightships, tall bridges, piers, monuments, and -other aerial obstructions have been responsible for a tremendous -destruction of migratory birds. Beams of the lanterns at light -stations have a powerful attraction for nocturnal travelers of the -air that may be likened to the fascination for lights that also -is shown by many insects, particularly night-flying moths. The -attraction is not so potent in clear weather, but when the atmosphere -is moisture laden, as in a heavy fog, the rays have a dazzling effect -that lures the birds to their death. They may fly straight up the -beam and dash themselves headlong against the glass, or they may keep -fluttering around the source of the light until exhausted, and then -drop to the rocks or waves below. The fixed, white, stationary light -located 180 feet above sea level at Ponce de Leon Inlet (formerly -Mosquito Inlet), Fla., has caused great destruction of bird life -even though the lens is shielded by wire netting. On one occasion an -observer gathered up a bushel-basketful of warblers, sparrows, and -other small passerine birds that had struck during the night. The -birds apparently beat themselves to death against the wire or fell -exhausted to the concrete pavement below, frequently to be destroyed -there by cats or skunks. Two other lighthouses at the southern end -of Florida, Sombrero Key and Fowey Rocks, have been the cause of -a great number of bird tragedies, while heavy mortality has been -noted also at some of the lights on the Great Lakes and on the coast -of Quebec. It is the fixed white lights that cause such disasters -to birds, as the stations equipped with flashing or red lights do -not present such strong attractions. That it is not a mere case of -geographical location has been demonstrated, for it is observed that -when fixed white lights have been changed to red or flashing lights, -the migrating birds are no longer endangered. At some of the light -stations in England and elsewhere, shelves and perches have been -placed below the lanterns to afford places where birds can rest until -they have overcome their bewilderment. - -For many years at the National Capital, the Washington Monument, -although unilluminated, caused the destruction of large numbers of -small birds, due apparently to their inability to see this obstacle -in their path, towering more than 555 feet into the air. One morning -in the spring of 1902 the bodies of nearly 150 warblers, sparrows, -and other birds were found about its base. Then, as the illumination -of the city was improved and the Monument became more visible at -night, the loss became steadily less, until by 1920 only a few birds -would be killed during an entire migration. On November 11, 1931, -however, as part of the Armistice Day celebration, batteries of -brilliant floodlights grouped on all four sides about the base of the -Monument were added to the two searchlights already trained on the -apex, so that the lighted shaft probably corresponds in brilliancy -to a very low magnitude lighthouse lantern. Airplane pilots have -ventured opinions that on a clear night it could be seen for 40 -miles. It is certain that there is an extensive area of illumination, -and on dark nights, when there are gusty, northerly winds and the -nocturnal travelers seem to fly at lower altitudes, many of them are -attracted to the Monument as to a lighthouse beacon. As they approach -from the north a last-minute attempt to avoid it causes them to -veer off to the east or the west where they are literally sucked in -and dashed against the southern face of the shaft. During the fall -migration of 1932 more than 500 warblers, vireos, thrushes, kinglets, -sparrows, and others were killed. Since that year the mortality has -been less, but the Monument at times remains a serious menace to -birds during migration and some are killed nearly every fall. - -When the torch on the Statue of Liberty in New York Harbor was kept -lighted, it caused an enormous destruction of bird life, tabulations -showing as many as 700 birds killed in a single month. - -In September 1948, bird students were startled by news of the -wholesale destruction of Maryland yellowthroats, redstarts, -ovenbirds, and others that were dashed against the 1,250-foot -high Empire State Building in New York City, the 491-foot high -Philadelphia Saving Fund Society Building in Philadelphia, and the -450-foot high WBAL radio tower in Baltimore. In New York the birds -continued to crash into the Empire State Building over a 6-hour -period and their bodies were scattered over a four-block area. The -mortality was so heavy in Philadelphia that it was impossible to -use the sidewalk below the sky-scraper until the birds had been -gathered. A study of the weather conditions prevailing at this -time in the Atlantic coastal region suggests the probable cause -of this catastrophe. By early morning on September 11 a mass of -cold, southward-flowing air had just reached New York City where -it was forcing upward and was being overridden by a mass of warm, -northward-flowing air. Presumably the migrants were riding the upper -levels of the southbound current which, in the contact zone with the -northbound current, was being deflected earthward, thus causing the -birds to fly lower and lower until they were below the tower of the -Empire State Building. Clouds and gusty winds in the zone of contact -between the two air masses reduced visibility and disrupted avian -navigation with the result that the confused travelers crashed into -the stone and steel obstruction. As the cold air mass continued to -move southward, the situation was repeated at Philadelphia and at -Baltimore. - - -=Exhaustion= - -Although it would seem that the exertion incident to the long -flights of many species of migratory birds would result in their -arrival at their destination in a state bordering on exhaustion, -this is contrary to the truth. Both the soaring and the sailing of -birds show them to be proficient in the use of factors employed in -aerial transportation that only recently have become understood and -imitated by aeronautical engineers. The use of ascending currents -of air, employed by all soaring birds, and easily demonstrated by -observing the gulls that glide hour after hour along the windward -side of a ship, are now utilized by man in his operation of gliders. -Moreover, the whole structure of a bird renders it the most perfect -machine for extensive flight that the world has ever known. Hollow, -air-filled bones, making an ideal combination of strength and -lightness, and the lightest and toughest material possible for -flight in the form of feathers, combine to produce a perfect flying -machine. Mere consideration of a bird's economy of fuel or energy -also is enlightening. The golden plover, traveling over the oceanic -route, makes the entire distance of 2,400 miles from Nova Scotia to -South America without stop, probably requiring about 48 hours of -continuous flight. This is accomplished with the consumption of less -than 2 ounces of fuel in the form of body fat. To be as economical in -operation, a 1,000-pound airplane would consume in a 20-mile flight -not the gallon of fuel usually required, but only a single pint. - -The sora, or Carolina rail, which is such a notoriously weak flyer -that at least one writer was led to infer that most of its migration -was made on foot, has one of the longest migration routes of any -member of the family, and easily crosses the wide reaches of the -Caribbean Sea. The tiny ruby-throated hummingbird crosses the Gulf of -Mexico in a single flight of more than 500 miles. - -While birds that have recently arrived from a protracted flight -over land or sea sometimes show evidences of being tired--as, for -example, pintail ducks that have flown from the North American -mainland to the Hawaiian Islands--their condition is far from being -a state of exhaustion. With a few hours' rest and a crop well -filled with proper food, most birds exhibit eagerness to resume -their journey. The popular notion that birds find the long ocean -flights excessively wearisome and that they sink exhausted when -terra firma is reached, generally does not agree with the facts. -The truth lies in the opposite direction, as even small land birds -are so little averse to ocean voyages that they not only cross the -Gulf of Mexico at its widest point, but may even pass without pause -over the low, swampy coastal plain to the higher regions beyond. -Under favorable conditions birds can fly when, where, and how they -please. Consequently the distance covered in a single flight is -governed chiefly by the food supply. Exhaustion, except as the result -of unusual factors, cannot be said to be an important peril of -migration. - - - - -_Influence of the Weather on Migration_ - - -The state of the weather at any point has little if anything to do -with the time of arrival of migratory birds. This is contrary to the -belief of observers who have thought that they could foretell the -appearance of various species by a study of the weather conditions. -Though the insistent crescendo note of the ovenbird is ordinarily -associated with the full verdure of May woods, this bird has been -known to reach its breeding grounds in a snowstorm and the records -of its arrival in southern Minnesota show a temperature variation -from near freezing to full summer warmth. Temperatures at arrival of -several other common birds vary from 14 degrees between highest and -lowest temperatures to 37 degrees, the average variation being about -24 degrees. - -It should be remembered that North American species spending the -winter months in tropical latitudes experience no marked changes in -climatic conditions from November to March or April, yet frequently -they will start the northward movement in January or February. This -is in obedience to physiological promptings and has no relation to -the prevailing weather conditions. For migratory birds the winter -season is a period of rest, a time when they have no cares other -than those associated with the daily search for food or escape from -their natural enemies. Their migrations, however, are a vital part -of their life cycles, which have become so well adjusted that the -seasons of travel correspond in general with the major seasonal -changes on their breeding grounds. With the approach of spring, -therefore, the reproductive impulse awakens, and each individual bird -is irresistibly impelled to start the journey that ends in its summer -home. - -In other words, the evidence indicates that the urge to migrate -is so ingrained that each species moves north in spring when the -average weather that will be encountered is not unendurable. The -word "average" must be emphasized since it appears obvious that the -migrations of birds have so evolved that in general they synchronize -with average climatic conditions. The hardy species travel early, -fearless of the blasts of retreating winter, while the more delicate -kinds come later when there is less danger of encountering prolonged -periods of inclement weather. Some of the hardy birds pause in -favorable areas and allow the spring season to advance. Then, by -rapid travel they again overtake it, or, as sometimes happens, they -actually outstrip it. Occasionally this results in some hardship, -and rarely in the destruction of large numbers of individuals. Cases -are known where early migrating bluebirds have been overwhelmed by -late winter storms. Nevertheless, unless such climatic conditions are -prolonged, no serious effect on the species is noted. The soundness -of the bird's instincts is evidenced by the fact that natural -catastrophes, great though they may be, do not permanently diminish -the avian populations. - -As has been pointed out, the advance of average temperature lines, -known as isotherms, is found to correspond closely with the northward -movements of certain species. For example, the northward travels -of the Canada goose are found to coincide with the advance of the -isotherm of 35° F. (fig. 4). - -The spring flight of migrants, if interrupted for any reason, is -resumed when weather conditions again become favorable, and it is -probable that all instances of arrival of birds in stormy weather -can be explained on the theory that the flight was begun while the -weather was auspicious. The state of the weather when a flight starts -at any southern point, the relation of that place to the average -position of the bird under normal weather conditions on that date, -and the average rate of migratory flight, are data basic to any -reasonably accurate prediction of the time arrival may be expected in -northern areas. - -Head winds are as unfavorable to migration as is rain or snow, as -they greatly increase the labor of flight and cut down the speed of -cross-country travel. If such winds have a particularly high velocity -they may force down the weaker travelers, and when this happens over -water areas, large numbers of birds are lost. Even strong winds that -blow in the direction of aerial travel are unfavorable for the birds, -as they interfere with their balance and disarrange their feathers. -Moderate tail winds and cross or quartering breezes appear to offer -the best conditions for the passage of the migrants. - - - - -_Problems of Migration_ - - -=Banding studies= - -The study of living birds by the banding method, whereby great -numbers of individuals are marked with numbered aluminum leg rings, -has come to be recognized as a most accurate means of ornithological -research. Since 1920, banding work in North America has been under -the direction of the Fish and Wildlife Service in cooperation -with the Dominion Wildlife Service of Canada. Every year voluntary -cooperators, working under permit, place bands on thousands of birds, -game and nongame, large and small, migratory and nonmigratory, -each band carrying a serial number and the legend, NOTIFY FISH AND -WILDLIFE SERVICE, WASHINGTON, D. C., or on the smaller sizes an -abbreviation thereof. When a banded bird is reported from a second -locality, a definite fact relative to its movements becomes known, -and a study of many cases of this nature develops more and more -complete knowledge of the details of migration. - -The records of banded birds are also yielding other pertinent -information relative to their migrations, such as the exact dates -of arrival and departure of individuals, the length of time that -different birds pause on their migratory journeys to feed and rest, -the relation between weather conditions and the starting times for -migration, the rates of travel of individual birds, the degree of -regularity with which birds return to the exact summer or winter -quarters used in former years, and many other details that could -be learned in no other manner. Banding stations that are operated -systematically throughout the year, therefore, are supplying much -information concerning the movements of migratory birds that -heretofore could only be surmised. (See Appendix II, p. 92 for -instructions on reporting the recovery of banded birds.) - - -=Movements of residents= - -Typical migration consists of definite movements that are repeated -regularly year after year, and it is to these that the term is -generally restricted. It is desirable, however, if only for purposes -of comparison, that some account be taken of the movements of some -other birds, which, while not typical, do possess some of the -characteristics of true migration. Data on this subject are being -collected through bird banding. - -There are several species that are customarily grouped under the -heading "permanent residents," the term implying that these birds -do not travel but remain throughout the year in one locality. -Among these are the cardinal, the tufted titmouse, the wrentit, -the Carolina wren, the house finch, the bobwhite, the California -quail, and the ruffed grouse. Each species may be present constantly -throughout the year, although in the northern part of the range there -is probably a slight withdrawal of the breeding birds in winter. The -individuals to be seen at that season, therefore, may not always be -the same as those observed during the summer. It is certain, however, -that these species do not regularly perform extensive journeys. - -While the blue jay is disposed to be secretive, it is such a showy -and noisy bird that it is not likely to escape notice. In the -vicinity of Washington, D. C., as in many other places, it is present -the year round, but at the end of September or early in October -when the weather is becoming cooler, troops of jays are sometimes -seen working southward through the trees. A corresponding northward -movement occurs again in May. This is unquestionably a migration to -and from some winter range, but its extent or significance is not now -known. Some light is being shed on the matter, however, through the -records of banded birds, and these eventually will fill in a more -perfect picture of the movements of this species. One jay, banded on -September 14, 1923, at Waukegan, Ill., was killed at Peruque, Mo., -on November 15 of the same year; another, banded at Winnetka, Ill., -on June 16, 1925, was retaken at Sulphur Rock, Ark., the following -December 10; a third, banded on May 6, 1925, at Whitten, Iowa, was -recaptured at Decatur, Ark., on January 22, 1926. These three birds -unquestionably had made a flight that had every appearance of being a -true migration to winter quarters in Missouri and Arkansas. - -The black-capped chickadee is apparently resident in many places, but -occasionally in winter it invades the range of the southern Carolina -chickadee, and in northern Canada it is regularly a migrant. - -In the coastal plain between Washington, D. C., and the Atlantic -Ocean, the white-breasted nuthatch is usually absent during the -summer, nesting at that season in the higher, or piedmont, country. -Late in fall, however, it appears in fair abundance in the wooded -bottoms, remaining at the lower levels until the following March or -April. - -Some birds, including the screech owl, bobwhite, Carolina wren, -and mockingbird, seem to be actually sedentary, but even these are -sometimes given to post-breeding wanderings. Ordinarily bobwhites -that are marked with numbered bands are seldom retaken far from the -area where banded, but sometimes they will travel 10 miles or more. -A screech owl banded at Glenwood, Minn., in March, was recovered -the following December at Emmetsburg, Iowa, 180 miles south. Such -flights, however, are probably more in the nature of a search for -new feeding areas, or to escape from a winged enemy, than a true -migratory journey. - - -=Migration of the white-throated sparrow= - -The white-throated sparrow, one of the most abundant members of its -family, breeds from northern Mackenzie and the southern part of the -Ungava Peninsula south to southern Montana, northern Pennsylvania, -and Massachusetts. The winter range extends from the southern part -of the breeding range south to the Gulf coast and northeastern -Mexico. It is therefore a common migrant in many sections. Since it -is a ground-feeding bird and is readily attracted to the vicinity of -dwellings, it has been banded in large numbers, the total to November -14, 1949, being nearly 283,500. It would be expected that these would -yield a comparable number of return records that would furnish basic -data relative to the migrations of the species. Such, however, is -not the case. Banded white-throated sparrows are rarely recaptured -at stations between the breeding and wintering grounds. Operators of -stations in the winter area, as Thomasville, Ga., and Summerville, -S. C., have obtained return records showing that these birds do come -back to the exact winter quarters occupied in previous seasons. The -fact that they do not again visit banding stations on their migration -routes indicates some unusual aspects of their travels, which it is -hoped will eventually be discovered by banding studies. Problems -of this type constitute definite challenges to the student of bird -migration. - - -=Migration of the yellow-billed loon= - -The semiannual movements of the yellow-billed loon present an unusual -problem in migration. It breeds along the Arctic coast, probably -from Cape Prince of Wales eastward to Franklin Bay, and also in the -interior of northern Canada south to Clinton-Colden, Aylmer, and -Artillery Lakes, where it is rather common. It has been reported -as already present by May 25 at the mouth of the Liard River, in -southwestern Mackenzie. This coincides with the time that first -arrivals are noted fully 700 miles north, at Point Barrow, Alaska. -The problem has been to ascertain the route used by these birds to -their principal nesting grounds in the interior. - -For a long time it was believed that this big diver did not winter in -large numbers anywhere on the Pacific coast, and it had been supposed -that the spring route extended 2,000 miles northeastward from a -wintering ground somewhere in eastern Asia to Bering Strait, then 500 -miles still northeast to round Point Barrow, then 500 miles east to -the coast of Mackenzie, and finally 700 miles south--in spring--to -the region near the eastern end of Great Slave Lake. - -The yellow-billed loon is a powerful flier, and it is probable that -this suggested route is correct for those birds that breed in the -northern coastal regions. A reasonable doubt may be entertained, -however, whether the breeding birds of Great Slave Lake and -contiguous areas reach their breeding grounds by the 700-mile flight -south from the Arctic coast. Within recent years it has been found -that these birds are fairly common in the maze of channels and -islands off the coast of southeastern Alaska as late as the last of -October and in February. Possibly they are present there during the -period from November through January also, or they may at that time -move farther off shore and so escape detection. If this region is -an important wintering ground, as seems probable, then it is likely -that the breeding birds of the interior reach their nesting grounds -by a flight eastward across the mountains, a trip that is well within -their flying ability, rather than by a circuitous route around the -northern coast. The air-line distance from southeastern Alaska to the -mouth of the Liard River is in fact less than the distance to that -point from the mouth of the Mackenzie. - -Differing routes to various parts of a large breeding or wintering -ground, and used by large groups of individuals of other species, -are not unknown. For example, the redhead duck is one of the common -breeding ducks of the Bear River marshes of Utah, where a great many -have been banded each summer. The recovery records of banded redheads -show that while many travel westward to California, others start -their fall migration in the opposite direction and, flying eastward -across the Rocky Mountains, either turn southeast across the plains -to the Gulf of Mexico, or deliberately proceed in a northeasterly -direction to join the flocks of this species moving toward the -Atlantic coast from the prairie regions of southern Canada. - - - - -_Conclusions_ - - -The migration of birds as it is known today had its beginning in -times so remote that its origins have been entirely obscured, and -it can be interpreted now only in terms of present conditions. The -causes underlying migration are exceedingly complex. The mystery -that formerly cloaked the periodic travels of birds, however, has -been largely dispelled through the fairly complete information that -is now available concerning the extent and times of the seasonal -journeys of most of the species. Many gaps, however, still remain -in our knowledge of the subject. Much has been learned, and present -knowledge is being placed on record, but it must be left to future -study to clear away many of the uncertainties that continue to make -bird migration one of the most fascinating subjects in the science of -ornithology. - -Each kind of bird seems to have its own reaction to its environment, -so that the character of movement differs widely in the various -species, and seldom do any two present the same picture. In -fact, bird migration has been described as a phase of geographic -distribution wherein there is a more or less regular seasonal -shifting of the avian population caused by the same factors that -determine the ranges of the sedentary species. If this view is -correct, then it must be recognized that the far-reaching works of -man in altering the natural condition of the earth's surface can so -change the environment necessary for the well-being of the birds as -to bring about changes in their yearly travels. The nature and extent -of the changes wrought by man on the North American Continent are -easily apparent. Forests have been extensively cut away and their -places have been taken by second growth or cultivated land, and wide -stretches of prairie and plain have been broken up, irrigated, and -devoted to agriculture. These great changes are exerting a profound -effect upon the native bird populations, and the various species may -be either benefited or adversely affected thereby. - -The Federal Government has recognized its responsibility to the -migratory birds under changing conditions brought about by man, and -by enabling acts for carrying out treaty obligations, it is now -giving most species legal protection under regulations administered -by the Fish and Wildlife Service. Much is being done by legislation -for the welfare of the birds. The effectiveness of these conservation -laws, however, is increased in the same measure that the people of -the country become acquainted with the facts in the life histories of -the migrants and interest themselves personally in the well-being of -the various species. Long before the white man came to America the -birds had established their seasonal lanes of migration throughout -the Western Hemisphere. The economic, inspirational, and esthetic -values of these migratory species dictate that they be permitted -to continue their long-accustomed and still-mysterious habits of -migration from clime to clime. - - - - -Appendix I--_List of Birds Mentioned in the Text_ - - - Common name Scientific name - - American egret _Casmerodius albus egretta_ - Arctic tern _Sterna paradisaea_ - Atlantic brant _Branta bernicla hrota_ - Atlantic golden plover _Pluvialis dominica dominica_ - Bank swallow _Riparia riparia_ - Barn swallow _Hirundo rustica erythrogaster_ - Bartramian sandpiper or _Bartramia longicauda_ - upland plover - Belted kingfisher _Ceryle alcyon_ - Black-and-white warbler _Mniotilta varia_ - Black-billed cuckoo _Coccyzus erythropthalmus_ - Black brant _Branta bernicla nigricans_ - Black-capped chickadee _Parus atricapillus atricapillus_ - Black-crowned night heron _Nycticorax nycticorax hoactli_ - Black duck _Anas rubripes_ - Black-headed grosbeak _Pheucticus melanocephalus_ - Blackpolled warbler _Dendroica striata_ - Black-throated blue warbler _Dendroica caerulescens_ - Bluebird _Sialia sialis_ - Blue goose _Chen caerulescens_ - Blue jay _Cyanocitta cristata_ - Bluethroat _Cyanosylvia suecica_ - Blue-winged teal _Anas discors_ - Bobolink _Dolichonyx orizivorus_ - Bobwhite _Colinus virginianus_ - Bohemian [greater] waxwing _Bombycilla garrulus pallidiceps_ - Brewer's blackbird _Euphagus cyanocephalus_ - Broad-winged hawk _Bueto platypterus_ - Bronzed grackle _Quiscalus guiscula versicolor_ - Brown [tree] creeper _Certhia familiaris_ - Cackling [Canada] goose _Branta canadensis minima_ - California quail _Lophortyx californica_ - Canada goose _Branta canadensis_ - Canvasback _Aythya valisineria_ - Cape May warbler _Dendroica tigrina_ - Cardinal _Richmondena cardinalis_ - Carolina chickadee _Parus carolinensis_ - Carolina wren _Thryothorus ludovicianus_ - Chimney swift _Chaetura pelagica_ - Chipping sparrow _Spizella passerina_ - Chuck-wills-widow _Caprimulgus carolinensis_ - Clark's nutcracker _Nucifraga columbiana_ - Cliff swallow _Petrochelidon pyrrhonota_ - Common tern _Sterna hirundo_ - Cooper's hawk _Accipiter cooperi_ - Coot [American] _Fulica americana_ - Cowbird _Molothrus ater_ - Crossbill _Loxia curvirostra_ - Crow _Corvus brachyrhynchos_ - Duck hawk [peregrine falcon] _Falco peregrinus_ - Eastern fox sparrow _Passerella iliaca iliaca_ - Eider _Somateria mollissima_ - Emperor goose _Philacte canagica_ - Evening grosbeak _Hesperiphona vespertina_ - European blackbird _Turdus merula merula_ - Field sparrow _Spizella pusilla_ - Forster's tern _Sterna forsteri_ - Frigate [man-o'-war] bird _Fregata magnificens_ - Golden-crowned kinglet _Regulus satrapa_ - Golden plover _Pluvialis apricaria_ - Golden-winged warbler _Vermivora chrysoptera_ - Goshawk _Accipiter gentilis_ - Grackle _Quiscalus quiscula_ - Gray-cheeked thrush _Hylocichla minima_ - Greenland wheatear _Oenanthe oenanthe leucorhoa_ - Harris's sparrow _Zonotrichia querula_ - Hermit thrush _Hylocichla guttata_ - Herring gull _Larus argentatus_ - Horned lark _Eremophila alpestris_ - Horned owl _Bubo virginianus_ - House finch _Carpodacus mexicanus_ - Ipswich sparrow _Passerculus princeps_ - Jacksnipe [see Wilson's snipe] _Capella gallinago delicata_ - Junco _Junco hyemalis_ - Kentucky warbler _Oporonis formosus_ - Kingbird _Tyrannus tyrannus_ - Knot _Calidris canutus_ - Kodiak fox sparrow _Passerella iliaca hyperborea_ - Lapland longspur _Calcarius lapponicus_ - Lapwing _Vanellus vanellus_ - Lesser yellowlegs _Totanus flavipes_ - Little blue heron _Florida caerulea_ - Loggerhead shrike _Lanius ludovicianus_ - Long-billed marsh wren _Telmatodytes palustris_ - Mallard _Anas platyrhynchos_ - Maryland yellowthroat _Geothlypis trichas trichas_ - Meadowlark _Sturnella magna_ - Migratory quail _Coturnix coturnix_ - Mockingbird _Mimus polyglottos_ - Mourning dove _Zenaidura macroura_ - Myrtle warbler _Dendroica coronata_ - Nighthawk _Chordeilies minor_ - Noddy tern _Amous stolidus_ - Northern phalarope _Lobipes lobatus_ - Northern robin _Turdus migratorius migratorius_ - Orchard oriole _Icterus spurius_ - Ovenbird _Seiurus aurocapillus_ - Pacific [American] golden _Pluvialis dominica fulva_ - plover - Parasitic jaeger _Stercorarius parasiticus_ - Peregrine falcon [duck hawk] _Falco peregrinus_ - Pine Grosbeak _Pinicola enucleator_ - Pine warbler _Dendroica pinus_ - Pintail _Anas acuta tzitzihoa_ - Pipit _Anthus spinoletta_ - Poor-will _Phalaenoptilus nuttallii_ - Purple finch _Carpodacus purpureus_ - Purple martin _Progne subis_ - Purple sandpiper _Erolia maritima_ - Raven _Corvus corax_ - Red-eyed vireo _Vireo olivaceus_ - Redhead _Aythya americana_ - Red-legged kittiwake _Rissa brevirostris_ - Redpoll _Acanthis flammea_ - Redstart _Setophaga ruticilla_ - Red-tailed hawk _Buteo jamaicensis_ - Red-winged blackbird _Agelaius phoeniceus_ - Robin _Turdus migratorius_ - Rock wren _Salpinctes obsoletus_ - Rose-breasted grosbeak _Pheucticus ludovicianus_ - Ross's goose _Chen rossi_ - Ross's gull _Rhodostethia rosea_ - Rosy finch _Leucosticte tephrocotis_ - Rough-legged hawk _Buteo lagopus_ - Ruby-throated hummingbird _Archilochus colubris_ - Ruffed grouse _Bonasa umbellus_ - Rusty blackbird _Euphagus carolinus_ - Sanderling _Crocethia alba_ - Scarlet tanager _Piranga olivacea_ - Scaup _Aythya marila_ - Screech owl _Otus asio_ - Sharp-shinned hawk _Accipiter striatus_ - Shumagin fox sparrow _Passerella iliaca unalaschensis_ - Slate-colored junco _Junco hyemalis_ - Snow bunting _Plectrophenax nivalis_ - Snow goose _Chen hyperborea_ - Snowy heron _Leucophoyx thula_ - Snowy owl _Nyctea scandiaca_ - Song sparrow _Melospiza melodia_ - Sooty fox sparrow _Passerella iliaca fuliginosa_ - Sooty tern _Sterna fuscata_ - Sora or Carolina rail _Porzana Carolina_ - Southern robin _Turdus migratorius achrusterus_ - Starling _Sturnus vulgaris_ - Swainson's hawk _Buteo swainsoni_ - Swamp sparrow _Melospiza georgiana_ - Townsend's fox sparrow _Passerella iliaca townsendi_ - Tree sparrow _Spizella arborea_ - Tufted titmouse _Parus bicolor_ - Turkey vulture _Cathartes aura_ - Turnstone _Arenaria interpres_ - Upland plover [Bartramian _Bartramia longicauda_ - sandpiper] - Valdez fox sparrow _Passerella iliaca sinuosa_ - Vesper sparrow _Pooecetes gramineus_ - Western palm warbler _Dendroica palmarum palmarum_ - Western tanager _Piranga ludoviciana_ - Western wood pewee _Contopus richardsonii_ - White-breasted nuthatch _Sitta carolinensis_ - White-throated sparrow _Zonotrichia albicollis_ - White-winged scoter _Melanitta fusca_ - Widgeon _Mareca americana_ - Williamson's sapsucker _Sphyrapicus thyroideus_ - Wilson's [common] snipe _Capella gallinago delicata_ - Winter wren _Troglodytes troglodytes_ - Woodcock _Scolopax rusticola_ - Wood thrush _Hylocichla mustelina_ - Worm-eating warbler _Helmitheros vermivorus_ - Wrentit _Chamaea fasciata_ - Yakutat fox sparrow _Passerella iliaca annectens_ - Yellow-billed cuckoo _Coccyzus americanus_ - Yellow-billed loon _Gavia adamsii_ - Yellow-headed blackbird _Xanthocephalus xanthocephalus_ - Yellow palm warbler _Dendroica palmarum hypochrysea_ - Yellow warbler _Dendroica petechia_ - - - - -Appendix II--_Bird Banding_ - - -Frequent reference has been made in this bulletin to bird banding -as a means for obtaining information on the migrations and life -histories of birds. Since 1920 this work in North America has been -under the direction of the Fish and Wildlife Service in cooperation -with the Dominion Wildlife Service of Canada. Each year birds to the -number of a quarter of a million or more may be marked with numbered -bands. - -As anyone interested in birds, either game or nongame, may have a -marked individual come into his hands, there are several pertinent -details that should be remembered if the recovery record is to have -maximum value in advancing the science of ornithology. - -1. The reporting letter should be addressed to: Bird Banding Office, -Patuxent Research Refuge, Fish and Wildlife Service, Laurel, Md. - -2. In the letter print the full number of the band, including the -series designation and the serial number. The series designation may -be a single letter or a two- or three-digit number and may be stamped -to the left or over the serial number. The series designation, if -a number such as "48" or "50," is not a date and should not be -so interpreted. Full numbers are correctly written as: A-678901; -48-345920; 141-543678; 20-167; 496-00517; etc. - -3. If the bird is alive and uninjured, read the number carefully -without removing the band, and release the bird. It may be reported -again. If it is dead, remove the band and, after flattening it out, -attach it to the letter with scotch tape or surgical adhesive tape. -Should it be desired as a souvenir, it will be returned upon request. - -4. Give in the report the exact date, the location (town, county, -State, etc.) and the manner in which the bird was obtained, that is, -whether it was shot, found dead, trapped, etc. - -5. Print your own name and permanent address clearly on the letter. - -6. Keep a record of the band number and refer to it should there be -any subsequent correspondence about it with the Service. The number -is always the clue to any record of a banded bird. - -Some bands may bear the inscription "Notify F. and Wildlife Service, -Washington, D. C." or "Notify Biological Survey, Washington, D. C.," -and on the smaller sizes these may be abbreviated to "F. and W. Serv. -Wash. D. C." or "Biol. Surv. Wash. D. C." - -All reports of the recovery of banded birds will be acknowledged with -the name of the bird, the date and place where it was banded, and the -name and address of the bander. - -The banding of birds is done by regular officers of the United -States and Dominion Services, by biologists and technicians of the -States and Provinces, and by volunteer cooperators who are specially -licensed under the provisions of the Migratory Bird Treaty Act. The -banding of migratory waterfowl is largely restricted to Federal and -State officers and is done chiefly in refuge areas. Most nongame -birds are banded by volunteer cooperators who are scattered over the -United States, Canada, and Alaska. The bands are furnished without -charge by the Service but each station operator supplies his own -traps and other equipment. - -To participate in this work, certain rules must be adhered to. -Applicants for banding permits: - -1. Must be at least 18 years of age. - -2. Must be thoroughly competent to identify positively all local -birds. - -3. Must have their ability vouched for by three recognized -ornithologists or by other banders. - -Application blanks for the Federal permits required may be obtained -from the Bird Banding Office, Patuxent Research Refuge, Fish and -Wildlife Service, Laurel, Md., or, in Canada, from the Chief, -Dominion Wildlife Service, Ottawa, Ontario. - - - - -_Bibliography_ - - -Since almost every faunal paper on birds has a bearing on the subject -of migration, only a few can be listed in this publication. Those -included were selected to aid the student wishing to pursue the -subject further and to cover not only all cited in the text but also -others consulted and used in its preparation. - -Allard, H. A. - - 1928. Bird migration from the point of view of light and length of - day changes. Am. Naturalist 62, pp. 385-408. - -Austin, O. L., Jr. - - 1928. Migration-routes of the Arctic tern (_Sterna paradisaea_ - Brunnich). Northeastern Bird Banding Assn. Bull., vol, 4, pp. - 121-125. - -Baird, S. F. - - 1866. The distribution and migration of North American birds. Am. - Jour. Sci., vol. 41, pp. 78-90, 184-192, 337-347. - -Bergtold, W. H. - - 1926. Avian gonads and migration. The Condor, vol. 28, pp. 114-120. - -Bissonette, Thomas Hume - - 1936. Normal progressive changes in the ovary of the starling - (_Sturnus vulgaris_) from December to April. The Auk, vol. 53, - pp. 31-50, illus. - - 1939. Sexual photoperiodicity in the blue jay (_Cyanocitta - cristata_). Wilson Bull., vol. 51, pp. 227-232, pis. 9-11. - -Clark, Austin H. - - 1925. Animal flight. Sci. Monthly, vol. 20, pp. 5-20. Clarke, W. E. - - 1912. Studies in bird migration. 2 vol., illus. London. Cooke, May - Thacher - - 1937. Flight speed of birds. U. S. Dept. Agr. Cir. 428, 13 pp. - - 1945. Transoceanic recoveries of banded birds. Bird-Banding, vol. - 16, No. 4, pp. 123-129. - -Cooke, W. W. - - 1888. Report on bird migration in the Mississippi Valley in the - years 1884 and 1885. U. S. Dept. Agr., Div. Econ. Ornith. Bull. - 2, 313 pp., illus. - - 1904. Distribution and migration of North American warblers. U. S. - Dept. Agr., Div. Biol. Survey Bull. 18, 142 pp. - - 1904. The effect of altitude on bird migration. The Auk, vol. 21, - pp. 338-341. - - 1905a. Routes of bird migration. The Auk, vol. 22, pp. 1-11. - - 1905b. The winter ranges of the warblers (_Mniotiltidae_). The Auk, - vol. 22, pp. 296-299. - - 1906. Distribution and migration of North American ducks, geese, - and swans. U. S. Dept. Agr., Bur. Biol. Survey Bull, 26, 90 pp. - - 1908. Averaging migration dates. The Auk, vol. 25, pp. 485-486. - - 1910. Distribution and migration of North American shore birds. U. - S. Dept. Agr., Bur. Biol. Survey Bull. 35, 100 pp., illus. - - 1913a. Distribution and migration of North American herons and - their allies. U. S. Dept. Agr., Bur. Biol. Survey Bull. 45, 70 - pp., illus. - - 1913b. The relation of bird migration to the weather. The Auk, vol. - 30, pp. 205-221, illus. - - 1914. Distribution and migration of North American rails and their - allies. U. S. Dept. Agr. Bull. 128, 50 pp. illus, - - 1915a. Bird migration. U. S. Dept. Agr. Bull. 185, 47 pp., illus. - - 1915b. Bird migration in the Mackenzie Valley. The Auk, vol. 32, - pp. 442-459, illus. - - 1915c. Distribution and migration of North American gulls and their - allies. U. S. Dept. Agr. Bull. 292, 70 pp., illus. - - 1915d. The yellow-billed loon: A problem in migration. The Condor, - vol. 17, pp. 213-214. - -Coues, E. - - 1878. Birds of the Colorado Valley, a repository of scientific and - popular information concerning North American ornithology. U. S. - Dept. Interior Misc. Pub. II, 807 pp., illus. - -DeLury, Ralph E. - - 1938. Sunspot Influences. Jour. Royal Astron. Soc. of Can., pt. 1, - March 1938, pt. 2, April 1938, 50 pp. - -Dixon, Joseph - - 1916. Migration of the yellow-billed loon. The Auk, vol. 33, No. 4, - pp. 370-376. - -Eaton, Richard Jefferson - - 1933-34. The migratory movements of certain colonies of herring - gulls. Bird-Banding, vol. 4, No. 4, pp. 165-176; vol. 5, No. 1, - pp. 1-19; vol. 5, No. 2, pp. 70-84. - -Earner, Donald S. - - 1945. The return of robins to their birthplaces. Bird-Banding, vol. - 16, No. 3, pp. 81-99. - -Furlong, W. R. - - 1933. Land-birds in a gale at sea. Bird Lore, vol. 35, No. 5, pp. - 263-265. - -Gätke, H. - - 1895. Heligoland as an ornithological observatory, the results - of fifty years' experience. (Transl. from the German by R. - Rosenstock). 599 pp., illus. Edinburgh. - -Gordon, Donald A. - - 1948. Some considerations of bird migration: continental drift and - bird migration. Science, vol. 108, pp. 705-711. - -Griffin, Donald R. - - 1940. Homing experiments with Leach's petrels. The Auk, vol. 57, - No. 1, pp. 61-74. - - 1943. Homing experiments with herring gulls and common terns. - Bird-Banding, vol. 14, No. 1 and 2, pp. 7-33. - - 1944. The sensory basis of bird navigation. Quart. Rev. of Biol., - vol. 19, No. 1, pp. 15-31. - -Grinnell, J. - - 1931. Some angles in the problem of bird migration. The Auk, vol. - 48, pp. 22-32. - -Gross, A. O. - - 1927. The snowy owl migration of 1926-27. The Auk, vol. 44, pp. - 479-493, illus. - - 1947. Cyclic invasions of the snowy owl and the migration of - 1945-46. The Auk, vol. 64, No. 4, pp. 584-601. - -Harrison, T. H. - - 1931. On the normal flight speeds of birds. Brit. Birds, vol. 25, - pp. 86-96. Jaeger, Edmund C. - - 1948. Does the poor-will "hibernate"? The Condor, vol. 50, p. 45. - - 1949. Further observations on the hibernation of the poor-will. The - Condor, vol. 51, pp. 105-109. - -Lewis, Harrison F. - - 1937. Migrations of the American brant (_Branta bernicla hrota_). - The Auk, vol. 54, pp. 73-95. - -Lincoln, F. C. - - 1917. Bohemian waxwing (_Bombycilla garrula_) in Colorado. The Auk, - vol. 34, p. 341. - - 1922. Trapping ducks for banding purposes: with an account of the - results obtained from one waterfowl station. The Auk, vol. 39, - pp. 322-334, illus. - - 1924a. Banding notes on the migration of the pintail. The Condor, - vol. 26, pp. 88-90. - - 1924b. Returns from banded birds, 1920 to 1923, U. S. Dept. Agr. - Bull. - - 1268, 56 pp., illus. - - 1926. The migration of the cackling goose. The Condor, vol. 28, pp. - 153-157, illus. - - 1927a. Notes on the migration of young common terns. Northeastern - Bird Banding Assoc. Bull., vol. 3, pp. 23-28, illus. - - 1927b. Returns from banded birds, 1923 to 1926. U. S. Dept. Agr. - Tech. Bull. No. 32, 95 pp., illus. - - 1928. The migration of young North American herring gulls. The Auk, - vol. 45, pp. 49-59. - - 1934a. Distribution and migration of the redhead (_Nyroca - americana_). Trans. 20th Am. Game Conf., pp. 280-287, map. - - 1934b. The operation of homing instinct. Bird-Banding, vol. 5, No. - 4, pp. 149-155. - - 1935a. Ancestral highways of the sky. American Forests, vol. 41, - No. 4, pp. 157, 159, and 196, 4 figs. - - 1935b. The migration of North American birds. U. S. Dept. Agr. Cir. - 363, 72 pp., 29 figs., bibliog. - - 1935c. The waterfowl flyways of North America. U. S. Dept. Agr, - Cir. 342, 12 pp., illus. - - 1936. Trans-Atlantic flight of gull-billed tern. The Auk, vol. 53, - No. 3, - - 1937a. The enigma of bird migration. Sci. Digest, vol. 1. No. 5, - pp. 63-65. - - 1937b. Our greatest travelers. In "The Book of Birds," Nat. Geog. - Soc, vol. 2, pp. 301-350, 1937. - - 1939a. The migration of American birds. Doubleday, Doran & Co., New - York, pp. i-xii and 1-189, col. pl. i-xii, maps 1-22. - - 1939b. The individual vs. the species in migration studies. The - Auk, vol. 56, No. 3, pp. 250-254. - - 1940. When the dove travels. Outdoor Georgia, vol. 1. No. 4, pp. 9 - and 22 (1 map). - - 1941. The waterfowl flyways. "Wild Ducks," Am. Wildlife Inst., pp. - 20-29. - - 1942a. La migración de aves en el Hemisferio Occidental. Pub. - and dist. by Panam. Sec. of the Int. Comm. for the Protection - of Birds. Pp. 1-12, illus. (maps). Both Spanish and English - versions. - - 1942b. Migration routes and flyways. In "Ducks, Geese and Swans of - North America," by Francis H. Kortright, Am. Wildlife Inst., pp. - 47-53. - - 1944a. Regulation by flyways. Am. Rifleman, vol. 92, No. 11, pp. - 21-23, 26, illus. (3 maps). - - 1944b. Chimney swift winter range discovered. The Auk, vol. 61, No. - 4, pp. 604-609, map. - - 1945a. The mourning dove as a game bird. Fish and Wildlife Serv. - Cir. 10, pp. 1-8, illus. - - 1945b. Flyway regulations. Trans. 10th N. A. Wildlife Conf., pp. - 50-51. - - 1946. Keeping up with the waterfowl. Audubon Mag., vol. 48, No. 3, - pp. 194-205, 7 illus., 10 maps. Reprinted as Fish and Wildlife - Serv. Leaflet 294, April 1947, pp. 1-10. - - 1949. The Mississippi flyway. Lead-off chapter in "Wildfowling - in the Mississippi Flyway" ed. by Eugene V. Connett, D. Van - Nostrand Co., New York, pp. 1-18, map, 12 photos. - -Lowery, George H. - - 1945, Trans-Gulf spring migration of birds and the coastal hiatus. - Wilson Bull., vol. 57, No. 2, pp. 92-121, pis. 9, 10. - - 1946. Evidence of trans-Gulf migration. The Auk, vol. 63, No. 2, - pp. 175-211. - -McMillan, Neil T. - - 1938. Birds and the wind. Bird Lore, vol. 40, No. 6, 3 plates. - Reprinted Smithsonian Kept, for 1939, pp. 355-363. - -Magee, M. J. - - 1928. Evening grosbeak recoveries. Northeastern Bird Banding Assoc. - Bull., vol. 4, pp. 56-59. - -Main, John S. - - 1932. The influence of temperature on migration. Wilson Bull., vol. - 44, pp. 10-12. - -May, J. B. - - 1929. Recoveries of black-crowned night herons banded in - Massachusetts. Northeastern Bird Banding Assoc. Bull., vol. 5, - pp. 7-16, illus. - -Palmén, J. A. - - 1893. Report on the migration of birds. Transl. from the German - by C. W. Shoemaker. Smithsonian Inst. Ann. Rept., 1892, pp. - 375-396, illus. - -Phillips, J. C. and F. C. Lincoln - - 1930. American waterfowl: their present situation and the outlook - for their future. Houghton Mifflin Co., Cambridge, Mass., pp. - i-xv, 1-312, illus. - -Pough, Richard H. - - 1948. Out of the night sky. Audubon Mag., vol. 50, No. 6, pp. - 354-355, illus. - -Rense, William A. - - 1946. Astronomy and ornithology. Popular Astron., vol. 54, No. 2, - pp. 1-19. Robbins, Chandler S. - - 1949. Weather and bird migration. The Wood Thrush, vol. 4, No. 4, - pp. 130-144. - -Rowan, W. - - 1925. Relation of light to bird migration and developmental - changes. Nature [London] vol. 115, pp. 494-495. - - 1926. On photoperiodism, reproductive periodicity, and the annual - migrations of birds and certain fishes. Boston Soc. Nat. Hist. - Proc., vol. 38, pp. 147-189. - - 1930a. Experiments in bird migration. II. Reversed migration. Nat. - Acad. Sci. Proc, vol. 16, p. 520-525. - - 1930b. The mechanism of bird migration. Sci. Progress, vol. 25, pp. - 70-78. - - 1931. The riddle of migration. Williams & Wilkins, Baltimore, pp. - i-xiv, 1-151, illus. - -Snyder, L. L. - - 1943. The snowy owl migration of 1941-42. Wilson Bull. vol. 55, No. - 1, pp. 8-10. - -Taverner, P. A. - - 1935. Continental land masses and their effect upon bird life. The - Condor, vol. 37, pp. 160-162, 2 illus. - -Warner, Lucien H. - - 1931. The present status of the problems of orientation and homing - by birds. Quart. Rev. of Biol., vol. 6, No. 2, pp. 208-214. - -Watson, J. B., and K. S. Lashley - - 1915. An historical and experimental study of homing. Carnegie - Inst. Washington, Dept. Marine Biol. Papers, vol. 7, pp. 1-60, - illus. - -Wetmore, A. - - 1923. Migration records from wild ducks and other birds banded in - the Salt Lake Valley, Utah. U. S. Dept. Agr. Bull. 1145, 16 pp., - illus. - - 1926. The migration of birds. Harvard Univ. Press, Cambridge, - Mass., pp. i-viii, 1-217, illus. - - 1932. Bird migration. Sci. Monthly, vol. 34, pp. 459-462. - -Williams, George G. - - 1945. Do birds cross the Gulf of Mexico in Spring? The Auk, vol. - 62, No. 1, pp. 98-111, map. - - 1947. Lowery on trans-Gulf migration. The Auk, vol. 64, No. 2, pp. - 217-237. - -Winkenwerder, H. A. - - 1902. The migration of birds with special reference to nocturnal - flight. Wisconsin Nat. Hist. Soc. vol. 2 n. s. pp. 177-263, - illus. - -Wolfson, Albert - - 1940. A preliminary report on some experiments on bird migration. - The Condor, vol. 42, No. 2, pp. 93-99. - - 1945. The role of the pituitary, fat deposition, and body weight in - bird migration. The Condor, vol. 47, No. 3, pp. 95-127. - - 1948. Bird migration and the concept of continental drift. Science, - vol. 108, No. 2793, pp. 23-30. - -Woodbury, Angus M. - - 1941. Animal migration--periodic response theory. The Auk, vol. 58, - pp. 463-505. - -Yeagley, Henry L. - - 1947. A preliminary study of a physical basis of bird navigation. - Jour. Applied Physics, vol. 18, No. 12, pp. 1035-1063. - - -_Index_ - - - Advantages of migration, 6 - Aerial obstructions, 76 - Altitudes of travel, 26 - Ancestral home theory, 8 - Arctic route, 68 - Aristotle, 2, 4, 5 - Atlantic coast route, 53 - Atlantic oceanic route, 48 - - Baldpate, 62 - Banding studies, 81, 92 - Blackbird, 32, 33, 60 - Brewer's, 32 - European, 4 - red-winged, 22, 32, 33, 35, 37 - rusty, 70 - yellow-headed, 32 - Bluebird, 9, 34, 37, 81 - Bluethroat, 19 - Bobolink, 32, 55, 56 (map), 69, 70, 71 - Bobwhite, 32, 34, 82, 83 - Brant, 57, 58 - Atlantic, 57 - Black, 68 - Bullbat, 32 - Bunting, snow, 34 - - Canvasback, 58 - Cardinal, 34, 82 - Chickadee, 7, 72 - black-capped, 83 - Carolina, 83 - Chuck-wills-widow, 55 - Clarke, W. E., 4, 6 - Compsothlypidae, 32 - Conclusions, 85 - Continental drift, theory of, 11 - Coot, 55 - Coues, Elliott, 4 - Cowbird, 29 - Crane, 2, 4, 6, 16, 26, 27, 28 - Creeper, brown, 75 - Crossbill, 7, 32, 74 - Crow, 20, 22, 32 - Clark's, 73 - Cuckoo, black-billed, 55 - yellow-billed, 55 - - Diurnal migration, 15 - Diving birds, 16 - Dove, 4 - mourning, 19 - turtle, 2, 6 - Duck, 2, 15, 16, 19, 20, 21, 32, 33, 37, 42, 58, 60, 61, 62, 68 - black, 20, 33, 58, 61 - eider, 68 - scaup, 58 - sea, 59, 63 - - Eel, 29 - Egret, 73 - Eider, 68 - Evolution of migration routes, 70 - Exhaustion, 78 - - Falcon, peregrine, 19 - Fall flights, 37 - Finch, 43 - house, 82 - purple, 74 - rosy, 72 - Fishes, 29 - Flicker, 70 - Flight speed, 18 - Flycatcher, 15, 19, 31 - Fly ways, 46 - Atlantic, 49 (map), 58 - Mississippi, 50 (map) - Central, 51 (map) - Pacific, 52 (map) - - Gätke, Heinrich, 19 - Goose, 2, 4, 15, 16, 19, 20, 21, 33, 59, 60, 61, 62 - blue, 22, 32, 61, 62 - cackling, 63 - Canada, 15, 21, 22 (map), 32, 58, 59, 81 - emperor, 68 - Ross's, 64 (map) - snow, 32, 72 - Gordon, Donald A., 30 - Goshawk, 12 - Grackle, 37 - bronzed, 32 - Great Lakes route, 60 - Grebe, 34 - Grosbeak, 45, 74 - black-headed, 37 - evening, 74 - pine, 72 - rose-breasted, 33, 45, 46 (map) - Gross, Alfred O., 74 - Groups, movements of, 12 - Grouse, ruffed, 82 - Gull, 16, 68, 73, 78 - herring, 73 - Ross's, 68 - - Hawk, 2, 16, 19, 26, 34, 42 - broad-winged, 16 - Cooper's, 16 - duck, 19, 20 - red-tailed, 16 - rough-legged, 16 - sharp-shinned, 16 - Swainson's, 16 - Herodotus, 2 - Heron, 19, 20, 73 - black-crowned night, 73 - little blue, 73 - snowy, 73 - Hesiod, 2 - Hesperornis, 11 - Hibernation, 4 - Homer, 2 - Homing instinct, 30 - Hummingbird, ruby-throated, 79 - - Ichthyornis, 11 - Influence of weather, 80 - Insects, 29 - - Jacksnipe, 37 - Jaeger, Edmund C., 5 - Jaeger, parasitic, 68 - Jay, blue, 34, 83 - Junco, 10, 34, 72 - slate-colored, 37, 70, 75 - - Kingbird, 32, 42, 55 - Kingfisher, belted, 34 - Kinglet, 77 - golden-crowned, 75 - Kite, 4 - Kittiwake, red-legged, 68 - Knot, 11, 42 - - Lapwing, 28 - Lark, horned, 19 - meadow, 34, 76 - Lewis, Harrison F., 57 - Lincoln, Frederick C., 5 - Long distance migrations, 38 - Longspur, 34, 76 - Lapland, 37, 75 - Loon, 16 - yellow-billed, 84, 85 - - Mackenzie Valley route, 60 - Magnetic sense, 30 - Magnus, Olaus, 4 - Mallard, 22, 31, 33, 58 - Man-o'-war bird, 30 - Martin, purple, 12 - Migration, advantages of, 6 - altitudes, 26 - distances, 38 - diurnal, 15 - fall, 37 - historical accounts, 4 - long distance, 38 - mystery of, 4 - nocturnal, 15 - origin, 7 - perils, 75 - problems, 81 - routes, 41 - segregation during, 31 - short, 34 - species and groups, 12 - speed, 18 - theories of causes, 7 - undetermined, 34 - vagrant, 73 - variable, 35 - vertical, 72 - weather, 80 - Mississippi Valley route, 60 - Mockingbird, 83 - Movements of residents, 82 - Movements of species and groups, 12 - Murre, 29 - Mystery of migration, 4 - - Nighthawk, 9, 16, 32, 38, 55, 60, 70 - Nocturnal migration, 15 - Northern ancestral home theory, 8 - Nutcracker, Clark's, 73 - Nuthatch, 7 - white-breasted, 83 - - Orientation, 28 - Origin of migration, 7 - Oriole, 15 - orchard, 9 - Ovenbird, 70, 78, 80 - Owl, great horned, 34 - screech, 83 - snowy, 12, 74 - - Pacific coast route, 63 - Pacific oceanic route, 66 - Passerella iliaca, 35 - Pelican, 4, 16, 26 - Perils, aerial obstructions, 76 - exhaustion, 78 - migration, 75 - storms, 75 - Pewee, western wood, 72 - Phalarope, 33 - northern, 27 - Photoperiodism, theory of, 9 - Pigeon, homing, 30, 31 - Pintail, 22, 55, 62, 79 - Pipit, 73 - Pliny, 4 - Plover, 15 - golden, 11, 19, 48, 49, 51, 54 (map), 66, 68, 71, 79 - upland, 15 - Poor-will, 5 - Problems, migration, 81 - banding studies, 81 - migration of the white-throated sparrow, 84 - migration of the yellow-billed loon, 84 - movements of residents, 82 - - Quail, 2, 34 - California, 82 - migratory, 2 - - Rail, 4, 15 - Carolina, 79 - Raven, 19 - Redhead, 58, 62, 85 - Redpoll, 12 - Redstart, 14, 45, 47 (map), 70, 78 - Residents, movements of, 82 - Robin, 9, 22, 24, 33, 34, 35, 61, 70, 76 - Routes, 41, 53 (map) - Arctic, 68 - Atlantic coast, 53 - Atlantic oceanic, 48 - "bobolink," 55, 56 (map) - evolution of, 70 - flyways, 46 - Great Lakes, 60 - Great Plains, 62 - Mackenzie Valley, 60 - Mississippi Valley, 60 - narrow, 42 - Pacific coast, 63 - Pacific oceanic, 66 - Rocky Mountain, 62 - wide, 42 - Rowan, William, 10 - - Salmon, 29 - Sanderling, 11, 27 - Sandpiper, 15, 27 - Bartramian, 15 - purple, 42 - Sapsucker, Williamson's, 72 - Scaup, 58 - Scoter, 63 - white-winged, 59, 65 - Segregation, 31 - Shore bird, 9, 11, 12, 32, 33, 38, 42, 48, 50, 55, 57, 60, 61 - Short and undetermined migrations, 34 - Shrike, 19, 34 - loggerhead, 37 - Snipe, 15 - Wilson's, 37 - Snowbird, 10 - Sora, 79 - Southern ancestral home theory, 8 - Sparrow, 15, 31, 32, 34, 60, 76, 77 - chipping, 37, 70 - field, 37 - fox, 35, 36 (map) - Harris's, 43 (map), 44, 45 - Ipswich, 43 - song, 33, 34 - swamp, 75 - tree, 34, 37, 75 - vesper, 37 - white-throated, 75, 84 - Species, movements of, 12 - Speed, flight, 18 - migration, 18 - Starling, 4 - Stork, 2, 4, 6, 27 - Storms, 75 - Swallow, 2, 4, 6, 9, 17, 18, 26, 32, 34, 57 - bank, 55 - barn, 20, 38, 60 - cliff, 16, 17 (map), 26, 38 - hibernating, 4 - Swan, 4 - Swift, 4, 16, 19, 20, 34 - chimney, 4, 32 - - Tanager, 55, 66 - scarlet, 33, 44 (map), 45 - western, 65 (map), 66, 67 (map) - Teal, blue-winged, 20, 55, 58, 60 - Tern, arctic, 11, 38, 39 (map), 40, 41, 68 - common, 40 - Forster's, 40 - noddy, 30 - sooty, 30 - Theories of migration, 7 - Thrush, 4, 15, 19, 21, 27, 31, 38, 60, 77 - gray-cheeked, 21, 23 (map), 55 - hermit, 75 - wood, 55 - Titlark, 73 - Titmouse, 34 - tufted, 82 - Transmutation, 5 - Turd us migratorius, 35 - Turnstone, 11 - Turtle [dove], 2, 6 - - Vagrant migration, 73 - Variable migrations within species, 35 - Vertical migration, 72 - Vireo, 15, 55, 75, 77 - red-eyed, 69 (map), 70 - Vulture, 26 - turkey, 34 - - Warbler, 15, 17, 18, 27, 60, 75, 76 - black and white, 12, 13 (map), 14 (map) - blackpolled, 16, 18, 24, 25 (map), 55, 60, 70 - black-throated blue, 14 - Cape May, 37 - golden-winged, 63 - Kentucky, 63 - myrtle, 61, 70 - palm, 37 - pine, 37 - summer, 21 - wood, 31, 32 - worm-eating, 63 - yellow, 14, 21, 70 - Waterfowl, 20, 47, 55, 58, 59, 61, 64,93 - Waxwing, 32, 33 - Bohemian, 12, 74 - Weather, influence of, 80 - Wheatear, Greenland, 11 - Widgeon, 55 - American, 62 - Woodcock, 37 - Woodpecker, 34 - Wren, 15 - Carolina, 34, 82, 83 - long-billed marsh, 33 - rock, 37 - winter, 34, 75 - Wrentit, 82 - - Yeagley, Henry L., 30 - Yellowlegs, lesser, 21 - Yellowthroat, Maryland, 35, 78 - - - * * * * * - - -Transcriber Note - -Illustrations moved to prevent splitting paragraphs. Minor typos -corrected. - - - -*** END OF THE PROJECT GUTENBERG EBOOK USFWS CIRCULAR 16: MIGRATION OF -BIRDS (1950) *** - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the -United States without permission and without paying copyright -royalties. Special rules, set forth in the General Terms of Use part -of this license, apply to copying and distributing Project -Gutenberg-tm electronic works to protect the PROJECT GUTENBERG-tm -concept and trademark. Project Gutenberg is a registered trademark, -and may not be used if you charge for an eBook, except by following -the terms of the trademark license, including paying royalties for use -of the Project Gutenberg trademark. 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Lincoln</div> - -<div style='display:block; margin:1em 0'> -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online -at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you -are not located in the United States, you will have to check the laws of the -country where you are located before using this eBook. -</div> - -<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: USFWS Circular 16: Migration of Birds (1950)</div> - -<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Author: Frederick C. Lincoln</div> - -<div style='display:block; margin:1em 0'>Release Date: May 01, 2021 [eBook #65173]</div> - -<div style='display:block; margin:1em 0'>Language: English</div> - -<div style='display:block; margin:1em 0'>Character set encoding: UTF-8</div> - -<div style='display:block; margin-left:2em; text-indent:-2em'>Produced by: Tom Cosmas from materials made available on The Internet Archive.</div> - -<div style='margin-top:2em; margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK USFWS CIRCULAR 16: MIGRATION OF BIRDS (1950) ***</div> - -<hr class="chap x-ebookmaker-drop" /> - -<div id="Cover" class="figcenter" style="width: 465px;"> - <img src="images/cover.png" alt="" /> - <p class="tdc smaller">MIGRATION of BIRDS<br /> - <br /> - CIRCULAR 16<br /> - FISH AND WILDLIFE SERVICE<br /> - UNITED STATES DEPARTMENT OF THE INTERIOR</p> -</div> - - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_I">-I-</span></p> - -<h2 class="nobreak" id="MIGRATION">MIGRATION -of BIRDS</h2> -</div> - -<div class="figcenter" id="title" style="width: 158px;"> - <img class="w100" src="images/title.png" width="158" height="120" alt="" /> -</div> - - -<h2>By FREDERICK C. LINCOLN</h2> - -<p class="tdc"><i>Biologist</i></p> - -<p class="caption3nb pmb4">Illustrated by BOB HINES</p> - - - -<p class="pmb4 gesperrt caption3nb">CIRCULAR 16</p> - -<p><span class="pagenum" id="Page_II">-II-</span></p> - - -<p class="pmt2 tdc"> -UNITED STATES DEPARTMENT OF THE INTERIOR, Oscar L. Chapman, <i>Secretary</i><br /> -<br /> -FISH AND WILDLIFE SERVICE, Albert M. Day, <i>Director</i><br /> -</p> - -<div class="pmt4 pmb4 figcenter" id="doi_logo" style="width: 114px;"> - <img class="w100" src="images/doi_logo.png" width="114" height="112" alt="" /> -</div> - - -<p class="tdc">UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1950<br /> -<span class="bt">For sale by the Superintendent of Documents, Washington 25, D. C. Price 30 cents</span></p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_III">-III-</span></p> - -<h2 class="nobreak" id="Contents">Contents</h2> -</div> - -<table class="tblcont" summary="ToC"> -<tr> - <td></td> - <td class="tdr smaller">Page</td> -</tr> -<tr> - <td class="tdl">The mystery of migration</td> - <td class="tdr"><a href="#The_Mystery_of_Migration">4</a></td> -</tr> -<tr> - <td class="tdl">Advantages of migration</td> - <td class="tdr"><a href="#Advantages_of_Migration">6</a></td> -</tr> -<tr> - <td class="tdl">The origin of migration</td> - <td class="tdr"><a href="#The_Origin_of_Migration">7</a></td> -</tr> -<tr> - <td class="tdl"> Northern ancestral home theory</td> - <td class="tdr"><a href="#Northern_ancestral">8</a></td> -</tr> -<tr> - <td class="tdl"> Southern ancestral home theory</td> - <td class="tdr"><a href="#Southern_ancestral">8</a></td> -</tr> -<tr> - <td class="tdl"> Theory of photoperiodism</td> - <td class="tdr"><a href="#photoperiodism">9</a></td> -</tr> -<tr> - <td class="tdl"> Theory of continental drift</td> - <td class="tdr"><a href="#continental_drift">11</a></td> -</tr> -<tr> - <td class="tdl">When birds migrate</td> - <td class="tdr"><a href="#When_Birds_Migrate">11</a></td> -</tr> -<tr> - <td class="tdl"> Movements of species and groups</td> - <td class="tdr"><a href="#Movements">12</a></td> -</tr> -<tr> - <td class="tdl"> Nocturnal and diurnal migration</td> - <td class="tdr"><a href="#Nocturnal">15</a></td> -</tr> -<tr> - <td class="tdl">How birds migrate</td> - <td class="tdr"><a href="#How_Birds_Migrate">18</a></td> -</tr> -<tr> - <td class="tdl"> Speed of flight and speed of migration</td> - <td class="tdr"><a href="#Speed">18</a></td> -</tr> -<tr> - <td class="tdl"> Altitude at which birds travel</td> - <td class="tdr"><a href="#Altitude">26</a></td> -</tr> -<tr> - <td class="tdl"> Orientation</td> - <td class="tdr"><a href="#Orientation">28</a></td> -</tr> -<tr> - <td class="tdl"> Segregation during migration</td> - <td class="tdr"><a href="#Segregation">31</a></td> -</tr> -<tr> - <td class="tdl">Where birds migrate</td> - <td class="tdr"><a href="#Where_Birds_Migrate">34</a></td> -</tr> -<tr> - <td class="tdl"> Short and undetermined migrations</td> - <td class="tdr"><a href="#Short">34</a></td> -</tr> -<tr> - <td class="tdl"> Variable migrations within species</td> - <td class="tdr"><a href="#Variable">35</a></td> -</tr> -<tr> - <td class="tdl"> Fall flights not far south of breeding ranges</td> - <td class="tdr"><a href="#Fall_flights">37</a></td> -</tr> -<tr> - <td class="tdl"> Long-distance migrations</td> - <td class="tdr"><a href="#Long_distance">38</a></td> -</tr> -<tr> - <td class="tdl">Routes of migration</td> - <td class="tdr"><a href="#Routes_of_Migration">41</a></td> -</tr> -<tr> - <td class="tdl"> Wide and narrow migration lanes</td> - <td class="tdr"><a href="#migration_lanes">42</a></td> -</tr> -<tr> - <td class="tdl"> The fly ways</td> - <td class="tdr"><a href="#The_flyways">46</a></td> -</tr> -<tr> - <td class="tdl"> Atlantic oceanic route</td> - <td class="tdr"><a href="#Atlantic_oceanic_route">48</a></td> -</tr> -<tr> - <td class="tdl"> Atlantic coast route and tributaries</td> - <td class="tdr"><a href="#Atlantic_coast_route">53</a></td> -</tr> -<tr> - <td class="tdl"> Mackenzie Valley—Great Lakes—Mississippi<br /> - Valley Route and tributaries</td> - <td class="tdr vbot"><a href="#Mackenzie_Valley">60</a></td> -</tr> -<tr> - <td class="tdl"> Great Plains—Rocky Mountain routes</td> - <td class="tdr"><a href="#Great_Plains">62</a></td> -</tr> -<tr> - <td class="tdl"> Pacific coast route</td> - <td class="tdr"><a href="#Pacific_coast">63</a></td> -</tr> -<tr> - <td class="tdl"> Pacific oceanic route</td> - <td class="tdr"><a href="#Pacific_oceanic_route">66</a></td> -</tr> -<tr> - <td class="tdl"> Arctic routes</td> - <td class="tdr"><a href="#Arctic_routes">68</a></td> -</tr> -<tr> - <td class="tdl">Evolution of migration routes</td> - <td class="tdr"><a href="#Evolution_of_Migration_Routes">70</a></td> -</tr> -<tr> - <td class="tdl">Vertical migration</td> - <td class="tdr"><a href="#Vertical_Migration">72</a></td> -</tr> -<tr> - <td class="tdl">Vagrant migration</td> - <td class="tdr"><a href="#Vagrant_Migration">73</a></td> -</tr> -<tr> - <td class="tdl">Perils of migration</td> - <td class="tdr"><a href="#Perils_of_Migration">75</a></td> -</tr> -<tr> - <td class="tdl"> Storms</td> - <td class="tdr"><a href="#Storms">75</a></td> -</tr> -<tr> - <td class="tdl"> Aerial obstructions</td> - <td class="tdr"><a href="#Aerial_obstructions">76</a></td> -</tr> -<tr> - <td class="tdl"> Exhaustion</td> - <td class="tdr"><a href="#Exhaustion">78</a></td> -</tr> -<tr> - <td class="tdl">Influence of the weather on migration</td> - <td class="tdr"><a href="#Influence_of_the_Weather_on_Migration">80</a></td> -</tr> -<tr> - <td class="tdl">Problems of migration</td> - <td class="tdr"><a href="#Problems_of_Migration">81</a></td> -</tr> -<tr> - <td class="tdl"> Banding studies</td> - <td class="tdr"><a href="#Banding_studies">81</a></td> -</tr> -<tr> - <td class="tdl"> Movements of residents</td> - <td class="tdr"><a href="#Movements_of_residents">82</a></td> -</tr> -<tr> - <td class="tdl"> Migration of the white-throated sparrow</td> - <td class="tdr"><a href="#Migration_white-throated_sparrow">84</a></td> -</tr> -<tr> - <td class="tdl"> Migration of the yellow-billed loon</td> - <td class="tdr"><a href="#Migration_yellow-billed_loon">84</a></td> -</tr> -<tr> - <td class="tdl">Conclusions</td> - <td class="tdr"><a href="#Conclusions">85</a></td> -</tr> -<tr> - <td class="tdl">Appendix I—List of birds mentioned in the text</td> - <td class="tdr"><a href="#Appendix_I">87</a></td> -</tr> -<tr> - <td class="tdl">Appendix II—Bird banding</td> - <td class="tdr"><a href="#Appendix_II">92</a></td> -</tr> -<tr> - <td class="tdl">Bibliography</td> - <td class="tdr"><a href="#Bibliography">94</a></td> -</tr> -<tr> - <td class="tdl">Index</td> - <td class="tdr"><a href="#Index">99</a></td> -</tr> -</table> - -<hr class="chap x-ebookmaker-drop" /> - - - -<p><span class="pagenum" id="Page_1"></span></p> - -<div class="chapter"> -<h1 class="nobreak">MIGRATION -of BIRDS</h1> -</div> - - -<p>When the birds that have nested in our dooryards and those that -have frequented the neighboring woods, hills, and marshes leave us in -the fall, the question naturally comes to mind: Where do they go? -This, however, is only one small part of the question as we also wonder: -Will the same ones return next spring to their former haunts? What -dangers will they face on their round-trip flight and while in their -winter homes? These and other questions on the migratory habits -of most species of Northern Hemisphere birds puzzle all who are -interested in them, whether it be the farmer who profits by their -tireless warfare against the weed and insect pests of his crops, the bird -student who enjoys an abundance and variety of feathered inhabitants -about him, or the hunter who wants a continuation from year to year -of the sport of wildfowling. Lack of information on the subject may -mean the loss of an important resource by unconsciously letting it slip -from us, as ignorance might be responsible for inadequate legal protection -for such species as might urgently need it. More general -knowledge on the subject will aid in the perpetuation of the various -migrants, the seasonal habitats of some of which are in grave danger -from man's utilization, sometimes unwisely, of the marsh, water and -other areas that were formerly homes for birds.</p> - -<p>The migrations of birds were probably among the first natural phenomena -to attract the attention and intrigue the imagination of man. -Recorded observations on the subject date back nearly 3,000 years, to -<span class="pagenum" id="Page_2">-2-</span> -the times of Hesiod, Homer, Herodotus, Aristotle, and others. In the -Bible there are several references to the periodic movements of birds, -as in the Book of Job (39:26), where the inquiry is made: "Doth the -hawk fly by Thy wisdom and stretch her wings toward the south?" -Jeremiah (8:7), wrote: "The stork in the heavens knoweth her appointed -time; and the turtle [dove], and the crane, and the swallow, -observe the time of their coming." And the flight of quail that saved -the Israelites from starvation in their wanderings in the wilderness of -Sinai is now recognized as a vast movement of migratory quail between -their breeding grounds and their winter home in Africa.</p> - -<p>Throughout the ages the return flights of migratory birds have been -important as a source of food after a lean winter and as the harbinger -of a change in season. The arrival of certain species has been heralded -with appropriate ceremonies in many lands, and among the Eskimos -and other tribes the phenomenon to this day is the accepted sign of the -imminence of spring and of warmer weather. The pioneer fur traders -in Alaska and Canada offered rewards to the Indian or Eskimo who -saw the first goose of the spring, and all joined in jubilant welcome to -the newcomer.</p> - -<p>As the North American Continent became more thickly settled, the -large flocks of ducks and geese that always had been hunted for food -became objects of the enthusiastic attention of an increasing army of -sportsmen. Most of the nongame species were found to be valuable -also as allies of the farmer in his never-ending warfare against weed -and insect pests. The need for laws protecting the valuable game and -nongame birds and for regulating the hunting of the diminishing game -species followed as a natural course. In the management of this wildlife -resource it has become obvious that continuous studies must be -made of the food habits of the various species, their environmental -needs, and their travels. Hence bird investigations are made by the -Fish and Wildlife Service, the bureau charged by Congress under the -Migratory Bird Treaty Act with the duty of protecting those species -that in their yearly journeys pass back and forth between the United -States and Canada, and between the United States and Mexico.</p> - -<p>For more than half a century the Fish and Wildlife Service and -its predecessor, the Biological Survey, have been collecting data on -the interesting and important phenomenon of the migration of North -American birds. The field men of the Service have gathered information -concerning the distribution and seasonal movements of the -<span class="pagenum" id="Page_3">-3-</span> -different species in many extended areas, from the Arctic coast south -to the pampas of Argentina. Supplementing these investigations is -the work of hundreds of volunteer ornithologists and bird students -throughout the United States and Canada, who each year, spring and -fall, forward to the Service reports on the migrations as observed in -their respective localities. Added to the mass of data thus assembled -is a rapidly growing recovery file of marked individuals. These data, -together with other carded records gleaned by the Fish and Wildlife -Service from a vast literature, constitute a series of files that now contain -well over 3,000,000 entries, easily the greatest existing accumulation -of information pertaining to the distribution and movements of North -American birds. Not only do the facts thus assembled form the basis -of regulatory action for the protection of the birds, but they also make -it possible to publish scientific accounts of the ranges and migrations -of the different species. They furnish the basis of this bulletin.</p> - -<p>The several important bird-protective measures adopted by State -and Federal Governments, particularly those having as their objectives -the conservation of the migratory song, insectivorous, and game species, -can be effective only if they have intelligent public support. To -increase such support, information must be more generally available -on that little understood but universally fascinating subject of bird -migration. A brief presentation of facts on the migratory habits of -the birds scientifically gathered by the Fish and Wildlife Service over -many years, will be helpful to bird-study classes, to conservation organizations, -and to farmers and others individually interested in the -welfare of the birds.</p> - -<p>In addition to his original investigations in the field and in the files -of the Fish and Wildlife Service, the author has made free use of the -writings of many other students of the subject. To all of these grateful -acknowledgment is made.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_4">-4-</span></p> - -<h2 class="nobreak" id="The_Mystery_of_Migration"><i>The Mystery of Migration</i></h2> -</div> - - -<p>Of observers whose writings are extant, Aristotle, naturalist and -philosopher of ancient Greece, was one of the first to discuss the -subject of bird migration. He noted that cranes traveled from the -steppes of Scythia to the marshes at the headwaters of the Nile, and -that pelicans, geese, swans, rails, doves, and many other birds likewise -passed to warmer regions to spend the winter. In the earliest years of -the Christian era, the elder Pliny, Roman naturalist, in his Historia -Naturalis, repeated much of what Aristotle had said on migration and -added comments of his own concerning the movements of the European -blackbird, the starling, and the thrushes.</p> - -<p>In spite of the keen perception shown in some of his statements -Aristotle also must be credited with the origin of some superstitious -beliefs that persisted for several centuries. One of these, that of -hibernation, became so firmly rooted that Dr. Elliott Coues (1878),<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">[1]</a> -one of America's greatest ornithologists, listed the titles of no less than -182 papers dealing with the hibernation of swallows. The hibernation -theory accounted for the autumnal disappearance of certain species -of birds by having them pass into a torpid state and so remain during -the cold season, hidden in hollow trees, caves, or in the mud of marshes. -Aristotle ascribed hibernation not only to swallows, but also to storks, -kites, doves, and others. Some early naturalists wrote fantastic accounts -of the flocks of swallows that allegedly were seen congregating -in the marshes until their accumulated weight bent into the water the -reeds on which they clung and thus submerged the birds. It was even -recorded that when fishermen in northern waters drew up their nets -they sometimes had a mixed "catch" of fish and hibernating swallows. -Clarke (1912) quotes Olaus Magnus, Archbishop of Upsala, who in -1555 published a work entitled "Historia de Gentibus Septentrionalis -et Natura," wherein he observed that if swallows so caught were taken -into a warm room they would soon begin to fly about but would live -only a short time.</p> - -<div class="footnote"> - -<p><a id="Footnote_1" href="#FNanchor_1" class="label">[1]</a> Publications referred to parenthetically by date are listed -in the <a href="#Bibliography">Bibliography, p. 94</a>.</p> - -</div> - -<p>The hibernation theory survived for more than 2,000 years and, until -the winter home of the chimney swift was discovered in 1944 through -the recovery of banded individuals, it was occasionally repeated by -credulous persons to account for the sudden disappearance of the immense -flocks that each autumn gather in southern Georgia and northern -<span class="pagenum" id="Page_5">-5-</span> -Florida. Although the winter range is still unknown in fullest -detail, Lincoln (1944b) has shown that some of these birds spend the -winter season in northeastern Peru.</p> - -<p>Although the idea that hibernation is a regular feature of the life -cycle of birds is no longer accepted for any species, recognition must be -accorded the observations of Edmund C. Jaeger of Riverside College, -Riverside, Calif. (1949). Earlier (1948), he had given a brief account -of the behavior of a poor-will found during the winter of 1946-47 in -the Chukawalla Mountains of the Colorado Desert, Calif., and which -was in a state of profound torpidity.</p> - -<p>What was presumably the same individual was found in the same -rock niche in a comatose condition on November 26, 1947. Beginning -on December 30, 1947, rectal temperatures were taken every 2 weeks, -the last on February 14, 1948. The temperature dropped from 67.6° -on the first date to 64.4° on January 18 and February 1, recovering to -65.8° on the late date of record. The weight decreased from 45.61 -grams on January 4 to 44.56 grams on February 14. An attempt to -detect heart beat by the use of a medical stethoscope was negative. No -movement of the chest walls could be detected and no moisture could be -collected on a cold mirror placed in front of the nostrils. Strong -light aimed directly into the pupil resulted in no response, not even an -attempt to close the eyelid. No waste matter was passed during the -entire period of observation and all evidence indicated that the bird -was in an exceedingly low state of metabolism.</p> - -<p>This bird was banded on January 5, 1948, with a Service band and -was back in the same rock niche on November 24, 1948, certainly the -second and probably the third season of return to this exact point. It -was there on December 5, 1948, but 2 weeks later it had disappeared, -probably the victim of some predator or an inquisitive human. Professor -Jaeger reports that the Hopi Indians call the poor-will -"Holchko," the sleeping one.</p> - -<p>Aristotle also was the originator of the theory of transmutation, -basing it upon the fact that frequently one species will arrive from the -north just as another species departs for more southerly latitudes. -From this he reasoned that although it was commonly believed that -such birds were of two different species, there really was only one, and -that this one assumed the different plumages to correspond with the -summer and winter seasons.</p> - -<p><span class="pagenum" id="Page_6">-6-</span></p> - -<p>Probably the most remarkable theory that has been advanced to -account for migration is contained in a pamphlet mentioned by Clarke -(1912: V. I, 9-11) as published in 1703 under the title: "An Essay -Toward the Probable Solution of this Question: Whence come the -Stork and the Turtle, the Crane, and the Swallow, when they Know -and Observe the Appointed Time of their Coming." It was written -"By a Person of Learning and Piety," whose "probable solution" was -that migratory birds flew to the moon and there spent the winter.</p> - -<p>Some peoples, who easily accepted the migratory travels of the -larger birds, were unable to understand how the smaller species, some -of them notoriously poor fliers, could make similar journeys. They -accordingly conceived the idea that the larger species, as the storks and -cranes, carried their smaller companions as living freight. In some of -the Mediterranean countries, it is still believed that these broad-pinioned -birds serve as aerial transports for the hosts of small birds that -congregate upon the shores awaiting opportunity for this kind of passage -to their winter homes in Africa. Similar beliefs have been found -among some tribes of North American Indians.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Advantages_of_Migration"><i>Advantages of Migration</i></h2> -</div> - - -<p>Before presenting some of the present theories concerning the origin -of bird migration, it seems well to consider briefly the ends that are -served by this annual round trip between breeding grounds and winter -quarters. It is apparent that the migratory habit enables a species to -enjoy the summers of northern latitudes while avoiding the severity -of the winters. In other words, migration makes it possible for some -species to inhabit two different areas during the seasons when each -presents favorable conditions. In the performance of its reproductive -duties, every pair of birds requires a certain amount of territory, the -extent of which varies greatly in different species. Generally, however, -this territory must be large enough to provide adequate food, not -only for the parent birds, but also for the lusty appetites that come -into being with the hatching of the eggs. Thus, if all birds were to -remain constantly either in tropical or in temperate regions, there -would be intolerable overcrowding during the breeding season. By -the spring withdrawal to regions uninhabitable earlier in the year, the -migrants are assured of adequate space and ample food upon their -<span class="pagenum" id="Page_7">-7-</span> -arrival in the winter-freed North, and it may be assumed that the -nonmigratory species that are resident in the South are also benefited -by the departure of the migrants.</p> - -<p>Nevertheless, it cannot be said that the winter or summer area of -every species is entirely unsuited to its requirements at other seasons, -for some individuals pass the winter season in areas that are frequented -only in summer by other individuals of their species. Such species -have extensive breeding ranges, presenting wide climatic variations, -so that some individuals may actually be resident in a region where -others of their kind are present only in winter.</p> - -<p>The tendency of some birds to move southward at the approach of -winter is not always due to the seasonal low temperatures, since experiments -have demonstrated that many of our summer insect feeders, -when confined in outdoor aviaries, comfortably withstand temperatures -far below zero. The main consideration is the depletion of the -food supply, caused either by the disappearance or the hibernation of -insects, or by the mantle of snow or ice that prevents access to the seeds -and other forms of food found on or close to the ground or submerged -in water. Possibly also the shortened hours of daylight materially -restrict the ability of the birds to obtain sufficient food at a time when -the cold requires an increased supply to maintain body heat. It is noteworthy -that some of our smaller birds, such as the chickadees, have -no fear of Arctic weather, as their food supplies are entirely arboreal -and so are always available. Also, when there is a good supply of -food in the form of pine and spruce seeds, nuthatches and crossbills -will remain through the winter in Canadian woods. When these -birds appear abundantly in winter at points in southern latitudes, it may -be concluded that there is a shortage of their food in the North.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="The_Origin_of_Migration"><i>The Origin of Migration</i></h2> -</div> - - -<p>Migration has long since become a definite hereditary habit that -recurs in annual cycles, probably because of physiological stimulus associated -with the reproductive period. Its origin is locked in the ages -of geologic time, but by study of the history of how birds came to -occupy their present ranges, information becomes available from which -reasonable theories may be developed and explored. The two that are -most commonly accepted are diametrically opposed to each other.</p> - -<p><span class="pagenum" id="Page_8">-8-</span></p> - - -<h3 id="Northern_ancestral">Northern ancestral home theory</h3> - -<p>According to one of these hypotheses, in earlier ages nonmigratory -birds swarmed over the entire Northern Hemisphere. At that time -the conditions of food and habitat were such as to permit them to -remain in their haunts throughout the year, that is, the entire northern -area then afforded the two important avian requirements—suitable -breeding conditions, and year-long food supply. This is the condition -today in the Tropics, and it is noteworthy that, as a rule, tropical birds -do not perform migrations. Gradually, however, in the Northern -Hemisphere the glacial ice fields advanced southward, forcing the birds -before them, until finally all bird life was concentrated in southern -latitudes. As the ages passed the ice cap gradually retreated, and each -spring the birds whose ancestral home had been in the North endeavored -to return, only to be driven south again at the approach of -winter. As the size of the ice-covered area diminished the journeys -made became ever longer until eventually the climatic conditions of -the present age became established and with them the habit of -migration.</p> - -<p>Thus, this theory supposes that today migratory birds follow the path -of a great racial movement that took place in a distant past and was -associated with the advances and recessions of the ice. The actions of -the birds themselves lend some support to this theory, as every bird student -has noted the feverish impatience with which certain species push -northward in spring, sometimes advancing so rapidly upon the heels -of winter that they perish in great numbers when overtaken by late -storms. It is probable that at this season the reproductive impulse is -a determining factor in driving the birds to their northern breeding -grounds.</p> - - -<h3 id="Southern_ancestral">Southern ancestral home theory</h3> - -<p>The opposing theory is simpler in some respects and supposes that -the ancestral home of all birds was in the Tropics and that, as all -bird life tends to overpopulation, there was a constant effort to seek -breeding grounds where the competition would be less keen. Species -that strove for more northern latitudes were kept in check by the ice -and were forced to return southward with the recurrence of winter -conditions. Gradually, as the ice retreated, vast areas of virgin country -became successively suitable for summer occupancy, but the winter -habitat remained the home to which the birds returned after the nesting -<span class="pagenum" id="Page_9">-9-</span> -season. It is a fact that some species spend very little time on -their breeding grounds; the orchard oriole, for example, spends only -2½ months in its summer home, arriving in southern Pennsylvania -about the first week in May and leaving by the middle of July.</p> - -<p>Both of these theories assume that migration is an ingrained habit, but -both have been criticized on biological and geological grounds, so -neither should be accepted without qualification as definitely accounting -for the origin of bird migration. It is apparent, however, that -whether the ancestral home of any species was at the northern or -southern limits of its present range, or even in some intermediate region, -the search for favorable conditions under which to breed in -summer and to feed in winter has been the principal factor underlying -the origin of migration.</p> - - -<h3 id="photoperiodism">Theory of photoperiodism</h3> - -<p>A modern view based on studies of living behavior, suggests also -that there is good reason for believing that migration is an annually -induced movement. If such be true then the theory of photoperiodism -as propounded by some recent investigators should receive some -consideration.</p> - -<p>This theory holds as its major premise that quantity of light and -length of day are the stimulating causes of migration. Its proponents -urge that migration is a phenomenon far too regular to be created anew -each season merely under stress of circumstances, such as need for food; -and that it begins before the necessity for a change in latitude becomes -at all pressing. Swallows, nighthawks, shore birds, and others may -start their southward movement while the summer food supply in the -North is at peak abundance; while robins, bluebirds, and others may -leave an abundant food in the South in spring and press toward northern -points when food supplies there are almost entirely lacking and -when severe cold and storms are likely to cause their wholesale destruction. -The regularity of arrival and departure is one of the most -impressive features of migration, and since birds travel in almost strict -accordance with the calendar, the proponents of the theory ask: "What -phenomenon to which we may attribute the stimulating impulse occurs -with such precise regularity as the constantly increasing amount of -light in spring?"</p> - -<p>Experimental work has abundantly demonstrated the effect of increased -light upon the growth, flowering, and fruiting of plants. -<span class="pagenum" id="Page_10">-10-</span> -Similarly, experiments with the common junco or snowbird reported -by Rowan (1931: 121), resulted in increased development of the sexual -organs by the end of December, although the birds were confined -in outdoor aviaries in Canada, and had been exposed to temperatures -as low as -44° F. From the first of November until early in January, -the juncos were subjected to ever-increasing light, supplied in the -aviaries by electric bulbs. As regards illumination, they were thus -artificially provided with conditions approximating those of spring. -At the close of this period, it was found that the sexual organs of the -birds had attained the maximum development normally associated -with spring. With gradual reduction of the lighting over a period -of little more than 1 month, the organs returned to their normal winter -condition.</p> - -<p>After a consideration of all evidence, including the fact that no ultra-violet -rays were used, it was concluded that the explanation lay in the -increased exercise taken during the periods of increased light. A -simple test whereby certain birds were forced by mechanical means -to take more exercise, the light being so reduced that there was merely -sufficient glow for them to see the advancing mechanism that forced -them into movement, showed that the rate of development of the -sexual organs exactly paralleled that in the birds that were exposed -to extended periods of illumination in the outdoor aviaries. Other -features in this experiment—such as the behavior of the birds themselves—also -indicated that more activity due to increased light is the -governing cause of the spring development of the sexual organs. If -this development be accepted as a controlling cause of migration, then -this experiment must be recognized as of great importance.</p> - -<p>Upon closer analysis, however, it is found that this theory, like those -before discussed, is open to serious objections. First, some of our -summer residents that migrate south for the winter do not stop in -equatorial regions, where they might find the periods of day and night -about equally divided, but push on beyond, some penetrating as far -south as Patagonia. Also it might be asked: "If the lengthening day -is the stimulating factor, why should our summer birds wintering in -the Tropics ever start northward, as in their winter quarters the variation -in the length of day from winter to summer is imperceptible?" -Like all the other theories advanced, this also, as at present understood, -is subject to unanswered criticism.</p> - -<p><span class="pagenum" id="Page_11">-11-</span></p> - - -<h3 id="continental_drift">Theory of continental drift</h3> - -<p>The theory of continental drift postulates an original northern land -mass, called Laurasia, and a southern one, called Gondwana. According -to this concept, each eventually broke into several segments -which eventually became the present continents. It is further assumed -that occasionally Laurasia and Gondwana drifted close to one another -or were at times in actual contact. On the basis of this geological -theory, Wolfson (1940) has attempted to explain the migrations of -some species of birds from one hemisphere to the other, as, for example, -the Greenland wheatear, Arctic tern, and several shore birds (turnstone, -sanderling, knot, golden plover, and others). Acceptance of this hypothesis -requires abandonment of the belief that the development of -migration was the result of useful ends that were served thereby, and in -its place, to give approval to the idea that migration was merely "the -natural consequence of an inherent behavior pattern responding to the -drifting of continental masses."</p> - -<p>It is a strange fact that although almost all professional paleontologists -are agreed that existing data oppose the theory of continental -drift, those who support it contend that their case is strengthened by -these same data. If, in the geologic history of the earth, there was any -such thing as continental drift, it appears from the evidence available -that it was before the Cretaceous period, estimated to have been about -70,000,000 years ago. Birds had then evolved but those known from -fossil remains were of extremely primitive types such as Hesperornis -and Ichthyornis. There is no evidence of the existence in that period -of any birds that were even closely related to any of those now living. -Accordingly, it is difficult to believe that the migratory patterns of -existing species have been determined by events that, if they did take -place, were at least 70,000,000 or more years ago.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="When_Birds_Migrate"><i>When Birds Migrate</i></h2> -</div> - - -<p>It is known that at any given point many species leave in the fall and -return in the spring. Since banding has had such wide application as -a method of study, it is known also that in some species one of the -parent birds (rarely both) frequently returns and nests in the tree, -bush, or box that held its nest in the previous season. One ordinarily -thinks of the world of birds as quiescent during two periods each year, -<span class="pagenum" id="Page_12">-12-</span> -at nesting time, and in winter. For individuals this is obviously the -case, but when the entire avifauna of the continent is considered it is -found that there are at almost all periods some latitudinal movements.</p> - - -<h3 id="Movements">Movements of species and groups</h3> - -<p>Some species begin their fall migrations early in July and in some -parts of the country distinct southward movements can be detected -from then until the beginning or middle of winter. For example, -many shore birds start south in the early part of July, while the -goshawks, snowy owls, redpolls, Bohemian waxwings, and many -others do not leave the North until forced to do so by the advent of -severe winter weather, or by lack of the customary food. Thus an -observer in the northern part of the United States may record an almost -unbroken southward procession of birds from midsummer to winter, -and note some of the returning migrants as early as the middle of -February. While on their way north, purple martins have been known -to arrive in Florida late in January and, among late arrivals, the northern -movement may continue into the first week of June. In some -species the migration is so prolonged that the first arrivals in the -southern part of the breeding range will have performed their parental -duties while others of that species are still on their way north.</p> - -<p>A study of these facts indicates that sometimes there exists a very -definite relationship between what we may term northern and southern -groups of individuals of the same species. A supposition is that for a -species with an extensive latitudinal breeding range, and which has a -normal migration, those individuals that nest farthest south migrate -first and proceed to the southern part of the winter range; those that -occupy the central parts of the breeding range migrate next and travel -to regions in the winter range north of those occupied by the first -group; and finally the individuals breeding farthest north are the last -to start their autumn migration and they remain farthest north during -the winter. In other words, this theory supposes that the southward -movement of the species is such that the different groups maintain their -relative latitudinal position with each other. The black and white -warbler furnishes an example. The breeding range of this bird extends -west and northwest from northern Georgia and South Carolina -to New Brunswick, extending also in a western and northwestern direction -as far as Great Bear Lake in northwestern Canada (<a href="#fig1">fig. 1</a>). It -<span class="pagenum" id="Page_13">-13-</span> -spends the winter in southern Florida, the West Indies, central Mexico, -Central America, and northwestern South America. In the southern -part of its breeding range it is nesting in April, but those that summer -in New Brunswick do not reach their nesting grounds before the -middle of May. Therefore, about 50 days are required for these northbound -birds to cross the breeding range, and if 60 days be allowed for -nest building, egg laying, incubation, care of young, and molt, they -would not be ready to start southward before the middle of July -(<a href="#fig2">fig. 2.</a>). Then another 50-day trip south, and the earliest migrants -from the northern areas would reach the Gulf Coast in September. -But both adults and young have been observed at Key West, Fla., by the -middle of July, and on the northern coast of South America by August -21. Since the birds at Key West were fully 500 miles south of the -breeding range, it is evident that they must have come from the southern -part of the nesting area.</p> - -<div class="figcenter" id="fig1" style="width: 473px;"> - <img class="w100" src="images/fig1.png" width="473" height="550" alt="" /> - <div class="caption"><i>Figure 1.</i>—Summer and winter homes of the black and white warbler, -a very slow migrant as the birds nesting in the northern part of the -country take 50 days to cross the breeding range. The speed of -migration is shown in <a href="#fig2">figure 2</a>. (<a href="#Page_14">See p. 14.</a>)</div> -</div> - -<p><span class="pagenum" id="Page_14">-14-</span></p> - -<div class="figcenter" id="fig2" style="width: 475px;"> - <img class="w100" src="images/fig2.png" width="475" height="451" alt="" /> - <div class="caption"><i>Figure 2.</i>—Isochronal migration lines of the black and white warbler, -showing a very slow and uniform migration. These birds apparently -advance only about 20 miles a day in crossing the United States. -(<a href="#Page_13">See p. 13.</a>)</div> -</div> - -<p>Many similar cases might be mentioned, such as the black-throated -blue warblers, which are still observed in the mountains of Haiti in -the middle of May, when others of this species are en route through -North Carolina to breeding territory in New England or have even -reached that region. Redstarts and yellow warblers, evidently the more -southern breeders, are seen returning southward on the northern coast -<span class="pagenum" id="Page_15">-15-</span> -of South America just about the time that the earliest of those breeding -in the North reach Florida on their way to winter quarters.</p> - - -<h3 id="Nocturnal">Nocturnal and diurnal migration</h3> - -<p>When one recalls that most birds appear to be more or less helpless -in the dark, it seems remarkable that many should select the night -hours for extended travel. Among those that do, however, are the -great hosts of shore birds, rails, flycatchers, orioles, most of the great -family of sparrows, the warblers, vireos, and thrushes, and in fact, the -majority of small birds. That it is common to find woods and fields -on one day almost barren of bird life, and on the following day filled -with sparrows, warblers, and thrushes, would indicate the arrival of -migrants during the night. Sportsmen sitting in their "blinds" -frequently observe the passage of flocks of ducks and geese, but great -numbers of these birds also pass through at night, the clarion call of -the Canada goose, or the conversational gabbling of a flock of ducks -being common night sounds in spring and fall in many parts of the -country. The sibilant, nocturnal calls of the upland plover or Bartramian -sandpiper and of other shore birds during their spring and fall -flights form vivid memories in the minds of many students of migration. -Observations made with telescopes focused on the full moon -have shown processions of birds, one observer estimating that birds -passed his point of observation at the rate of 9,000 an hour, which gives -some indication of the numbers of birds that are in the air during some -of the nights when migration is at its height. While the steady night-long -passage of migratory birds has been recorded, the bulk of the flocks -pass during the earlier hours of the evening and toward daylight in -the morning, the periods from 8 o'clock to midnight and from 4 to 6 -a. m. seeming to be favorite times for nocturnal flight.</p> - -<p>It has been claimed, with some reason, that small birds migrate by -night the better to avoid their enemies, and that most of the nocturnal -travelers are those that are naturally timid, sedentary, or feeble-winged. -To a certain extent this may be true as included in this group are not -only such weak fliers as the rails but also the small song and insectivorous -birds such as the wrens, the small woodland flycatchers, and other -species which, living habitually more or less in concealment, are probably -much safer making their flights under the protecting cloak of -darkness. Nevertheless, it must be remembered that night migrants -include also the snipe, sandpipers, and plovers, birds that are always -<span class="pagenum" id="Page_16">-16-</span> -found in the open, and are among the more powerful fliers, some of -them making flights of more than 2,000 miles across the ocean.</p> - -<p>Night travel is probably best for the majority of birds chiefly from -the standpoint of feeding. Digestion is very rapid in birds and yet the -stomach of one killed during the day almost always contains food. -To replace the energy required for long flight, it is essential that food -be obtained at comparatively short intervals, the longest of which -in most species is during the hours of darkness. If the smaller migrants -were to make protracted flights by day they would be likely to -arrive at their destination at nightfall almost exhausted, but since they -are entirely daylight feeders, they would be unable to obtain food until -the following morning. This would delay further flights and result -in great exhaustion or possibly even death were they so unfortunate -as to have their evening arrival coincident with unusually cold or stormy -weather. Traveling at night, they pause at daybreak and devote the -entire period of daylight to alternate feeding and resting. This permits -complete recuperation and resumption of the journey at nightfall.</p> - -<p>Many species of wading and swimming birds migrate either by day -or night, as they are able to feed at all hours, and are not accustomed -to seek safety in concealment. Some diving birds, including ducks -that submerge when in danger, sometimes travel over water by day -and over land at night. The day migrants include, in addition to some -of the ducks and geese, the loons, cranes, gulls, pelicans, hawks, swallows, -nighthawks, and the swifts. All of these are strong-winged -birds. The swifts, swallows, and nighthawks (sometimes called bullbats) -feed entirely on flying insects, and use their short, weak feet and -legs only for grasping a perch during periods of rest or sleep. Thus -they feed as they travel, the circling flocks being frequently seen in late -summer working gradually southward. Years ago before birds of -prey were so thoughtlessly slaughtered, great flocks of red-tailed. Swainson's, -and rough-legged hawks might be seen wheeling majestically -across the sky in the Plains States, and in the East the flights of broad-winged. -Cooper's, and sharp-skinned hawks are still occasionally seen. -To the birds of prey and possibly to the gulls also, a day's fasting now -and then is no hardship, particularly since they frequently gorge -themselves to repletion when opportunity is afforded.</p> - -<p><span class="pagenum" id="Page_17">-17-</span></p> - -<div class="figcenter" id="fig3" style="width: 476px;"> - <img class="w100" src="images/fig3.png" width="476" height="587" alt="" /> - <div class="caption"><i>Figure 3.</i>—Migration of the cliff swallow, a day migrant that instead -of flying across the Caribbean Sea as does the blackpolled warbler -(see <a href="#fig6">fig. 6</a>), follows around the coast of Central America, where food -is readily obtained. (<a href="#Page_25">See p. 25.</a>)</div> -</div> - -<p>An interesting comparison of the flights of day and night migrants -may be made through a consideration of the spring migrations of the -blackpolled warbler and the cliff swallow. Both spend the winter in -South America, at which season they are neighbors. But when the -impulse comes to start northward toward their respective breeding -grounds, the warblers strike straight across the Caribbean Sea to Florida -(<a href="#fig6">fig. 6</a>), while the swallows begin their journey by a westward flight -of several hundred miles to Panama (<a href="#fig3">fig. 3.</a>). Thence they move -leisurely along the western shore of the Caribbean Sea to Mexico, and -continuing to avoid a long trip over water, they go completely around -<span class="pagenum" id="Page_18">-18-</span> -the western end of the Gulf of Mexico. This circuitous route adds -more than 2,000 miles to the journey of the swallows that nest in Nova -Scotia. The question may be asked: "Why should the swallow select -a route so much longer and more roundabout than that taken by the -blackpolled warbler?" The simple explanation is that the swallow is -a day migrant while the warbler travels at night. The migration of -the warbler is made up of a series of long, nocturnal flights, alternated -with days of rest and feeding in favorable localities. The swallow, on -the other hand, starts its migration several weeks earlier and catches -each day's ration of flying insects during a few hours of aerial evolutions, -which at the same time carry it slowly in the proper direction. -Flying along the insect-teeming shores of the Gulf of Mexico, the 2,000 -extra miles that are added to the migration route are but a fraction -of the distance that these birds cover in pursuit of their daily food.</p> - -<p>Although most of our smaller birds make their longest flights at -night, close observation will show that travel is continued to some -extent by day. This is particularly true during the latter half of a migratory -season when the birds show evidence of an overpowering desire -to hasten to their breeding grounds. At this time flocks of birds while -feeding maintain a movement in the general direction of the seasonal -journey. Sometimes they travel hurriedly, and while their flights -may be short, they must cover an appreciable distance in the course -of a day.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="How_Birds_Migrate"><i>How Birds Migrate</i></h2> -</div> - - -<h3 id="Speed">Speed of flight and speed of migration</h3> - -<p>There is a widespread misconception concerning the speed at which -birds normally fly, and even regarding the speed they can attain when -occasion demands, as when closely pursued by an enemy. It is not -unusual to hear accounts of birds flying "a mile a minute." While -undoubtedly some birds can and do attain a speed even greater than -this, such cases are exceptional, and it is safe to say that even when -pressed, few can develop an air speed of 60 miles an hour. They do, -however, have two speeds, one being the normal rate for everyday purposes -and also for migration, and an accelerated speed for escape or -pursuit; this in some cases may be nearly double the normal rate of -movement. Nevertheless, it is doubtful if the effort required for the -high speeds could be long sustained, and certainly not for the long-distance -migratory journeys that are regularly made by most birds. -<span class="pagenum" id="Page_19">-19-</span> -The theory that migrating birds attain high speeds received encouragement -from the German ornithologist Gätke (1895), who for -many years made observations on birds at the island of Heligoland. -He postulated that the blue-throat, a species of thrush smaller than -the American hermit thrush, would leave African winter quarters at -dusk and reach Heligoland at dawn, which would mean a sustained -speed of 200 miles an hour, and that the American golden plover flew -from the coast of Labrador to Brazil in 15 hours, or at the tremendous -speed of 250 miles an hour. Most ornithologists now consider these -conclusions to be unwarranted.</p> - -<p>Sportsmen also often greatly overestimate the speed at which ducks -and geese fly and sometimes attempt to substantiate their estimates by -mathematical calculation, based upon the known velocity of a charge -of shot, the estimated distance and the estimated "lead" that was necessary -to hit the bird. If all three elements of the equation were known -with certainty, the speed of the bird could be determined with a fair -degree of accuracy. The majority of the ducks that are reported as -killed at 40, 50, or even 60 yards, however, actually are shot at distances -much less than estimated. To sight along a gun barrel and estimate -correctly the distance of a moving object against the sky is so nearly -impossible for the average gunner as to make such calculations of little -value.</p> - -<p>During the past few years reliable data on the speed of birds have -accumulated slowly. It has been found that a common flying speed -of ducks and geese is between 40 and 50 miles an hour, and that it is -much less among the smaller birds. Herons, hawks, horned larks, -ravens, and shrikes, timed with the speedometer of an automobile, have -been found to fly 22 to 28 miles an hour, while some of the flycatchers -are such slow fliers that they attain only 10 to 17 miles an hour. Even -such fast-flying birds as the mourning dove rarely exceed 35 miles an -hour. All these birds can fly faster, but it is to be remembered that at -training camps during World War I, airplanes having a maximum -speed of about 80 miles an hour easily overtook flocks of ducks that, -it may be supposed, were making every effort to escape. Aviators have -claimed that at 65 miles an hour they can overtake the fastest ducks, -though cases are on record of ducks passing airplanes that were making -55 miles an hour.</p> - -<p>The greatest bird speeds that have been reliably recorded are of the -swifts and the duck hawk, or peregrine falcon. An observer in an -<span class="pagenum" id="Page_20">-20-</span> -airplane in Mesopotamia reported that swifts easily circled his ship -when it was traveling at 68 miles an hour. To do this, the birds certainly -were flying at a speed as high as 100 miles an hour. Once a -hunting duck hawk, timed with a stop watch, was calculated to have -attained a speed between 165 and 180 miles an hour.</p> - -<p>The speed of migration, however, is quite different from that attained -in forced flights for short distances. A sustained flight of 10 -hours a day would carry herons, hawks, crows, and smaller birds from -100 to 250 miles, while ducks and geese might travel as much as 400 -to 500 miles in the same period. Measured as air-line distances, these -journeys are impressive and indicate that birds could cover the ordinary -migration route from the northern United States or even from northern -Canada to winter quarters in the West Indies or in Central America -or South America in a relatively short time. It is probable that individual -birds do make flights of the length indicated and that barn -swallows seen in May on Beata Island, off the southern coast of the -Dominican Republic, may have reached that point after a nonstop -flight of 350 miles across the Caribbean Sea from the coast of Venezuela. -Nevertheless, whether they continue such journeys day after -day is doubtful.</p> - -<p>It seems more likely that migrations are performed in a leisurely -manner, and that after a flight of a few hours the birds pause to feed -and rest for one or several days, particularly if they find themselves in -congenial surroundings. Some indication of this is found in the records -of banded birds, particularly waterfowl. Considering only the -shortest intervals that have elapsed between banding in the North and -recovery in southern regions, it is found that usually a month or more -is taken to cover an air-line distance of a thousand miles. For example, -a black duck banded at Lake Scugog, Ontario, was killed 12 days later -at Vicksburg, Miss. If the bird was taken shortly after its arrival, the -record would indicate an average daily flight of only 83 miles, a distance -that could have been covered in about 2 hours' flying time. Among -the thousands of banding records obtained in recent years, evidences -of such rapid flight are decidedly scarce, for with few exceptions all -thousand-mile flights have required 2 to 4 weeks or more. Among -sportsmen, the blue-winged teal is well known as a fast-flying duck -and quite a few of these banded on Canadian breeding grounds have -covered 2,300 to 3,000 miles in a 30-day period. Nevertheless, the majority -of those that have traveled to South America were not recovered -<span class="pagenum" id="Page_21">-21-</span> -in that region until 2 or 3 months after they were banded. Probably -the fastest flight over a long distance for one of these little ducks was -one made by a young male which traveled 3,800 miles from the delta -of the Athabaska River, in northern Alberta, Canada, to Maracaibo, -Venezuela, in exactly 1 month. This flight was at an average speed -of 125 miles per day. The greatest migration speed thus far recorded -for any banded bird is that of a lesser yellowlegs banded at North -Eastham, Cape Cod, Mass., on August 28, 1935, and killed 6 days later, -1,900 miles away, at Lamentin, Martinique, French West Indies. This -bird traveled an average daily distance of more than 316 miles.</p> - -<p>It seems certain that migratory journeys are performed at the normal -rate of flight, as this would best conserve the strength of the birds and -eliminate the fatigue that would result from effort required for great -speed. Migrating birds passing lightships and lighthouses, or crossing -the face of the moon, have been observed to fly without hurry or -evidence of straining to attain high speed.</p> - -<p>The speed of migration also is demonstrated by the dates of arrival, -particularly during the spring movement. The Canada goose affords -a typical example of regular, but slow migration. Its advance northward -at this season is at the same rate as the advance of the season -(<a href="#fig4">fig. 4</a>). In fact, the isotherm of 35° F. appears to be a governing -factor in the speed at which these geese move north, and over their -entire trip the vanguard follows closely the advance of this isotherm.</p> - -<p>Few species perform such regular migrations, many waiting in their -winter homes until spring is well advanced and then moving rapidly -to their breeding grounds. Sometimes this advance is so rapid that the -later migrants actually catch up with species that for a month or more -may have been pressing slowly but steadily northward.</p> - -<p>One of the best examples of rapid migration is found in the gray-cheeked -thrush. This bird winters in Colombia, Ecuador, Peru, Venezuela, -and British Guiana and does not start its northward journey -until many other species are well on their way. It does not appear in -the United States until the last of April—April 25 near the mouth of -the Mississippi, and April 30 in northern Florida (<a href="#fig5">fig. 5</a>). A month -later, or by the last week in May, the bird is seen in northwestern -Alaska, the 4,000-mile trip from Louisiana having been made at an -average speed of about 130 miles a day.</p> - -<div class="figcenter" id="fig4" style="width: 478px;"> - <img class="w100" src="images/fig4.png" width="478" height="437" alt="" /> - <div class="caption"><i>Figure 4.</i>—Migration of the Canada goose. The northward movement -keeps pace with the advance of spring, in this case the advance of -the isotherm of 35° F. agreeing with that of the birds.</div> -</div> - -<p><span class="pagenum" id="Page_22">-22-</span></p> - -<p>Another example of rapid migration is furnished by the yellow, or -summer, warbler. Coming from the Tropics, the birds reach New -Orleans about April 5, when the average temperature is 65° F. Traveling -north much faster than does the season, they reach their breeding -grounds in Manitoba the latter part of May, when the average temperature -is only 47°. Encountering progressively colder weather over -their entire route, they cross a strip of country in the 15 days from May -11 to 25 that spring temperatures take 35 days to cross. This "catching -up" with spring is habitual in species that winter south of the -United States and in most of the northern species that winter in the -Gulf States. To this rule there appear to be only six exceptions—the -Canada goose, the mallard, the pintail, the crow, the red-winged blackbird, -and the robin.</p> - -<p><span class="pagenum" id="Page_23">-23-</span></p> - -<div class="figcenter" id="fig5" style="width: 479px;"> - <img class="w100" src="images/fig5.png" width="479" height="481" alt="" /> - <div class="caption"><i>Figure 5.</i>—Isochronal migration lines of the gray-cheeked thrush, an -example of rapid migration. The distance from Louisiana to Alaska -is about 4,000 miles and is covered at an average speed of about -130 miles a day. The last part of the journey is covered at a speed -that is several times what it is in the Mississippi Valley.</div> -</div> - -<p>The blue goose presents a striking example of a late but very rapid -spring migration. Practically all members of the species winter in the -great coastal marshes of Louisiana, where 50,000 or more may be seen -grazing in the "pastures" or flying overhead in flocks of various sizes. -Their breeding grounds are chiefly on Baffin Island and on Southampton -Island in the northern part of Hudson Bay, in a region where conditions -of severe cold prevail except for a few weeks each year. The -birds seem to realize that even though the season in their winter quarters -is advancing rapidly, their nesting grounds are still covered with -a heavy blanket of ice and snow. Accordingly they remain in the -coastal marshes until the last of March or the first of April, when the -local birds are already busily engaged with the duties of reproduction. -The flight northward is rapid, almost nonstop, so far as the United -States is concerned, for although the birds are sometimes recorded in -<span class="pagenum" id="Page_24">-24-</span> -large numbers in the Mississippi Valley, including eastern South -Dakota, and in southeastern Manitoba, there are few records anywhere -along the route of such great flocks as are known to winter in Louisiana. -When the birds arrive in the James Bay region of Canada they apparently -enjoy a prolonged period of rest, as they are not noted in the -vicinity of their breeding grounds until the first of June. During the -first 2 weeks of that month they pour into the tundra country by the -thousands, and each pair immediately sets about the business of rearing -a brood.</p> - -<p>The robin has been mentioned as a slow migrant, and as a species it -takes 78 days to make the 3,000-mile trip from Iowa to Alaska, a stretch -of country that is crossed by advancing spring in 68 days. In this case, -however, it does not mean that individual robins are necessarily slow, -for probably the northward movement of the species depends upon the -continual advance of birds from the rear, the first individuals arriving -in a suitable locality remaining to nest, while the northward movement -of the species is continued by those still to come.</p> - -<p>Special interest attaches to the great variation in the speed at which -birds travel in different sections of the broad flyway extending from -the Gulf of Mexico to the Arctic Ocean, by way of the Mississippi and -Mackenzie Valleys. The blackpolled warbler furnishes an excellent -example (<a href="#fig6">fig. 6</a>). This species winters in north-central South America -and migrates in April across the West Indies to Florida. From this -point some individuals fly northwest to the Mississippi Valley, north to -Manitoba, northwest to the Mackenzie River, and thence almost due -west to western Alaska. In tracing the long route of these birds it is -found that a fairly uniform average speed of 30 to 35 miles a day is -maintained from the Gulf to Minnesota. Then comes a spurt, for a -week later the blackpolls have reached the central part of the Mackenzie -Valley and by the following week they are observed in northwestern -Alaska. During the latter part of the journey, therefore, many -individuals must average more than 200 miles a day. They use 30 -days in traveling from Florida to southern Minnesota, a distance of -about 1,000 miles, and scarcely half that time to cover the remaining -2,500 miles to Alaska. It should be noted that the increased speed is -directly associated with the change in direction, the north-and-south -course in the Mississippi Valley being accomplished slowly while the -northwesterly course across Canada is made at a much greater speed. -Increased speed across western Canada to Alaska is also shown by many -<span class="pagenum" id="Page_25">-25-</span> -other birds. A study of all species traveling up the Mississippi Valley -indicates an average speed of about 23 miles a day. From southern -Minnesota to southern Manitoba 16 species maintain an average speed -of about 40 miles a day. From that point to Lake Athabaska, 12 species -travel at an average speed of 72 miles a day; while 5 others travel to -Great Slave Lake at 116 miles a day; and another 5 species cover 150 -miles a day to reach Alaska. This change is in correlation with a -corresponding variation in the isothermal lines, which turn northwestward -west of the Great Lakes.</p> - -<div class="figcenter" id="fig6" style="width: 472px;"> - <img class="w100" src="images/fig6.png" width="472" height="561" alt="" /> - <div class="caption"><i>Figure 6.</i>—Migration of the blackpolled warbler. The solid isochronal -lines show the places at which these birds arrive at the same time. As -the birds move northward these lines become farther apart, showing -that the warblers move faster with the advance of spring. From -April 30 to May 10 the average speed is about 30 miles a day, while -from May 25 to May 30 it is increased to more than 200 miles.</div> -</div> - -<p><span class="pagenum" id="Page_26">-26-</span></p> - -<p>As has been previously indicated, the advance of spring in the northern -interior is much more rapid than in the Mississippi Valley and on -the Gulf coast. In other words, in the North spring comes with a -rush and during the height of the migration season in Saskatchewan -the temperature in the southern part of the Mackenzie Valley just about -equals that in the Lake Superior area, which is 700 miles farther south. -Such conditions, coupled with the diagonal course of the birds across -this region of fast-moving spring, exert a great influence on migration -and are the chief factors in the acceleration of speed of travel.</p> - -<p>Variations in speed of migration in different parts of the country are -illustrated also by the movements of the cliff swallow (<a href="#fig3">fig. 3</a>), which -breeds from Mexico to Alaska and winters in Brazil and Argentina. -It would be expected in spring to appear in the United States first in -Florida and Texas then in the southern Rocky Mountain region, and -finally on the Pacific coast. As a matter of fact, however, the earliest -spring records come from north-central California, where the bird -usually is common before the first arrivals are observed in Texas or -Florida. The route taken, for many years a migration problem, was -solved when it was found that these swallows went around the Gulf of -Mexico rather than across it. The isochronal lines on the map show -the more rapid advance along the Pacific coast. By March 20, when -the vanguard has not quite reached the lower Rio Grande in Texas, -the species is already north of San Francisco in California.</p> - - -<h3 id="Altitude">Altitude at which birds travel</h3> - -<p>At one time students of bird migration held firmly to the theory that -normal migration takes place at heights above 15,000 feet, reasoning -(somewhat uncertainly) that flying becomes easier as altitude is gained. -Since the development of the airplane, however, and with it man's exploration -of the upper regions of the air, it has become common knowledge -that rarified atmosphere adds greatly to the difficulties of flight. -This is due not only to the reduction in oxygen (whether for gasoline -engine or the lungs of a bird) but also to the lack of buoyancy of the -rarified air. Such birds as vultures, pelicans, cranes, and some of the -hawks feel this the least, since compared with body weight the supporting -<span class="pagenum" id="Page_27">-27-</span> -surface of their wings is very great, but for the smaller and -shorter-winged birds lack of buoyancy at high altitudes presents a difficult -obstacle in flight. Even when flying close to the earth, small birds -have to keep their wings in rapid motion.</p> - -<p>Another postulate favoring the high-altitude flying theory was that -the wonderful vision of birds was their sole guidance during migratory -flights; and to keep landmarks in view the birds were obliged to fly -high, particularly when crossing wide areas of water. This will be -considered in greater detail under Orientation (p. 28), so here it will -be sufficient to say that birds rely only in part upon vision to guide -them on migration. Also, it is to be remembered that there are definite -physical limitations to the range of visibility even under perfect atmospheric -conditions. Chief of these is the curvature of the earth's surface. -Thus, if birds crossing the Gulf of Mexico to Louisiana and -Florida flew at a height of 5 miles, they would still be unable to see a -third of the way across. And yet this trip is made twice each year by -thousands of thrushes, warblers, and others.</p> - -<p>Actual knowledge of the altitude of migratory flight is scanty, though -estimates obtained by means of the telescope, and still more accurate -data resulting from altimeter observation from airplanes, are slowly -accumulating. It is, of course, obvious that some birds that cross -mountain ranges during migration must attain a great altitude. Observers -at an altitude of 14,000 feet in the Himalayas have recorded -storks and cranes flying so high that they could be seen only through -field glasses. Being beyond the range of unaided vision they must -have been at least 6,000 feet above the observers, or at an actual altitude -of 20,000 feet above sea level. Such cases, however, are exceptional -as aviators have reported that they rarely meet birds above an altitude -of 5,000 feet.</p> - -<p>It is now known that migration in general is performed below a -height of 3,000 feet above the earth. Some proof of this statement is -available. Observations made from lighthouses and other points of -vantage indicate that migrants commonly travel at altitudes of a very -few feet to a few hundred feet above sea or land. Sandpipers, sanderlings, -and northern phalaropes, observed in migration on the Pacific -oceanic route, have been noted to fly so low that they were visible only -as they topped a wave. Observers stationed at lighthouses and lightships -off the English coast have similarly recorded the passage of land -birds, which sometimes flew just above the surface of the water, and -<span class="pagenum" id="Page_28">-28-</span> -rarely above 200 feet. During the World Wars broad areas in the air -were under constant surveillance and among the airplane pilots and -observers many took more than a casual interest in birds. Of the -several hundred records resulting from their observations only 36 were -of birds flying above 5,000 feet, and only 7 above 8,500 feet. Cranes -were once recorded at an altitude of 15,000 feet, while the lapwing -was the bird most frequently seen at high levels, 8,500 feet being its -greatest recorded altitude.</p> - -<p>These observations naturally relate only to daytime travelers, but -there is no reason to believe that nocturnal migration is performed at -higher altitudes. The fact that many birds are killed each year by -striking the lanterns at lighthouses, or other man-made obstructions, -does not, however, furnish conclusive proof that low altitudes are generally -used during nocturnal flight, for it should be recalled that these -accidents occur chiefly in foggy or unsettled weather, and also that -powerful lights have a great attraction for many species of birds. The -altitude at which birds travel is affected by other weather conditions -also. For example, flight at the higher elevations is facilitated on -clear, warm days by the currents of warm air that ascend from broad -areas.</p> - - -<h3 id="Orientation">Orientation</h3> - -<p>There probably is no single aspect of the entire subject of bird migration -that challenges our admiration so much as the unerring certainty -with which birds cover thousands of miles of land and water to come -to rest in exactly the same spot where they spent the previous summer -or winter. The records from birds marked with numbered bands -offer abundant proof that the same individuals of many species will -return again and again to their identical nesting sites. These data -show also that many individuals migrate in fall over the same route, -year after year, making the same stops and finally arriving at the -precise thicket that served them in previous winters.</p> - -<p>The faculty that enables these birds to point their course accurately -over vast expanses of land and water may, for want of a better term, -be called a "sense of direction." Man recognizes this sense in himself, -though usually it is imperfect and frequently at fault. Nevertheless -the facility with which experienced hunters and woodsmen locate tiny -camps or other points in forested or mountainous country, frequently -cloaked by darkness or fog, with all recognizable landmarks obliterated -<span class="pagenum" id="Page_29">-29-</span> -seems due to this faculty. Ability to travel with precision over unmarked -trails is not limited either to birds or to man. It is likewise -possessed by many other mammals as well as by some insects and fishes, -the well-known migrations of the salmon and the eel being notable -examples.</p> - -<p>Ability to follow a more or less definite course to a definite goal is -evidently part of an inherited faculty. Both the path and the goal -must have been determined either when the habit originated or in the -course of its subsequent evolution. The theory is sometimes advanced -that the older and more experienced birds lead the way, showing the -route to their younger companions. This explanation may be acceptable -for some species, but not for those in which adults and the young -migrate at different times. The young cowbird that is reared by -foster parents flocks with others of its kind when grown and in many -cases can hardly be said to have adult guidance in migration. An inherited -migratory instinct with a definite sense of the goal to be reached -and the route to be followed must be attributed to these birds.</p> - -<p>It is well known that birds possess wonderful vision. If they also -have retentive memories subsequent trips over the route may well be -steered in part by recognizable landmarks. The arguments against -the theory of vision and memory are chiefly that much migration takes -place by night and that great stretches of the open sea are crossed without -hesitation. Nevertheless, the nights are rarely so dark that all -terrestrial objects are totally obscured, and such features as coastlines -and rivers are just those that are most likely to be seen in the faintest -light, particularly by the acute vision of the bird and from its aerial -points of observation. But some birds fly unerringly through the -densest fog. Members of the Biological Survey, proceeding by steamer -from the island of Unalaska to Bogoslof Island in Bering Sea, through -a fog that was so heavy as to make invisible every object beyond a -hundred yards, recorded the fact that flocks of murres, returning to -Bogoslof, after quests for food, broke through the wall of fog astern, -flew by the vessel, and disappeared into the mists ahead. The ship was -heading direct for the island by the use of compass and chart, but its -course was no more sure than that of the birds.</p> - -<p>Some investigators have asserted that the sense of direction has its -seat in the ears or nasal passages and thus that the bird is enabled to -identify air currents and other phenomena. It has been found that -disturbance of the columella or the semicircular canals of the inner ear -<span class="pagenum" id="Page_30">-30-</span> -will destroy the homing instinct of the racing pigeon, but experiments -in the form of delicate operations, or closing the ears with wax, prove -such a serious shock to the sensitive nervous system of the bird that -they cannot be considered as affording conclusive evidence. Several -years ago careful studies were made of the homing instinct of the sooty -and noddy terns, tropical species that in the Atlantic region reach their -most northern breeding point on the Dry Tortugas Islands, off the -southwest coast of Florida. They are not known to wander regularly -any appreciable distance farther north. It was found that some were -able to return to their nests on the Tortugas after they had been taken -on board ship, confined in cages below decks, and carried northward -to distances varying from 400 to 800 miles before being released. Landmarks -of all kinds were entirely lacking, and the birds certainly were -liberated in a region in which they had had no previous experience.</p> - -<p>Possibly the "homing instinct" as shown by these terns, by the man-o'-war -birds that are trained and used as message carriers in the Tuamotu, -Gilbert, and Marshall Islands, and by the homing pigeon, is not -identical with the sense of perceptive orientation that figures in the -flights of migratory birds. Nevertheless, it seems closely akin and is -probably caused by the same impulses, whatever they may be and -however they may be received. It should be remembered, however, -that while homing may involve flight from a point that the bird has -never before visited, the flight is always to a known point—that is, -the bird's nest—while, on the other hand, the first migratory flight -is always from the region of the bird's birth to a region it has never -before visited. The spring migration might, of course, be more nearly -considered as true "homing."</p> - -<p>Some students have leaned strongly toward the possible existence -of a "magnetic sense" as being the important factor in the power of -geographical orientation. The theory that migratory birds might -be responsive to the magnetic field of the earth was conceived as early -as 1855, when some experimental work was done in Russia, and nearly -60 years later in France. Recently investigations in this field have -been conducted by Yeagley (1947) and by Gordon (1948) with diametrically -opposite results. The idea carries with it the implication -that contained in the bird's body is an organ that is sensitive to the -effect of its motion through the vertical component of the magnetic -field and to other related factors. In the tests by Dr. Yeagley, 20 young -homing pigeons were given training flights to their home loft from -<span class="pagenum" id="Page_31">-31-</span> -distances up to 100 miles. Permanent magnets were then affixed to -the under side of the manus part of the wings of half of the birds while -copper plates of equivalent weight were attached to the wings of the -other half. All birds were released singly at an air-line distance of -about 65 miles from the loft. The results were most suggestive, as -only two of the birds carrying magnets returned to the loft, whereas -eight of the controls returned.</p> - -<p>With certain minor modifications, this experiment was repeated by -Gordon. In this case 60 pigeons were used and releases were made -from points up to 58 miles, where the direction of flight was such that -the birds had to navigate across the gradient of the magnetic field. -Every bird returned to its loft on the day of release regardless of -whether it carried magnets or unmagnetized bars of the same weight.</p> - -<p>Attempts to demonstrate the effect of radio waves on the navigational -ability of birds also have produced contradictory results. In some of -these tests, homing pigeons released near broadcasting stations have -appeared to be hopelessly confused, whereas in others, apparently conducted -in the same manner, no effects could be discerned. It is obvious -that before the electromagnetic theory can be accepted or rejected, -much additional experimental work is necessary.</p> - -<p>In concluding this discussion of orientation it is pertinent to point -out that the migratory instinct appears to be more or less transitory, -that it is not persistent over an extended period. Migratory birds may -be arrested en route, either by natural conditions, such as unusual food -supplies, or forcibly by the act of man, and detained until the end or -nearly the end of the migratory season, and then may not attempt -to finish the journey, apparently having lost the migratory impulse. -In the fall and early winter of 1929, abundant food and an open season -caused an unusual number of mallard ducks to arrest their migration -and remain in western Montana and northern Idaho. Later, however, -a heavy snowfall with subzero temperatures suddenly cut off the food -supply, with the result that great numbers of the birds starved to death, -when a flight of a few hours would have carried them to a region of -open water and abundant food.</p> - - -<h3 id="Segregation">Segregation during migration</h3> - -<p>During the height of the northward movement in spring the woods -and thickets may be suddenly filled with several species of wood -warblers, thrushes, sparrows, flycatchers, and others, which it is natural -<span class="pagenum" id="Page_32">-32-</span> -to conclude have traveled together and arrived simultaneously. Probably -they did, but such combined migration is by no means the rule -for all species.</p> - -<p>As a group the wood warblers (<i>Compsothlypidae</i>) probably travel -more in mixed companies than do any other single family of North -American birds. The flocks are likely to be made up of several species -in spring and fall with both adults and young. Sometimes swallows, -sparrows, blackbirds, and some of the shore birds also migrate in mixed -flocks. In fall, great flocks of blackbirds frequently sweep south across -the Plains States, and occasionally one flock will contain bronzed -grackles, red-winged blackbirds, yellow-headed blackbirds, and -Brewer's blackbirds.</p> - -<p>On the other hand many species keep strictly to themselves. It -would be difficult for any other kind of bird to keep in company with -one of such rapid movements as the chimney swift, which is rarely -found associated with any other species at any season. Nighthawks -or bullbats also fly in separate companies, as do usually crows, waxwings, -crossbills, bobolinks, and kingbirds. Occasionally, a flock of -ducks will be observed to contain several species, but generally when -they are actually on migration the individuals of each species separate -and travel with others of their own kind. The flocks of blue geese, -previously mentioned in connection with speed of flight (p. 22), frequently -have with them a few of the closely related snow geese, particularly -in the eastern part of their winter range. The portion here -is usually about 10 to 1, but farther west the numbers of snow geese -increase until they outnumber their blue relatives.</p> - -<p>The adults of most perching birds drive the young away when they -are grown, probably to be relieved of the necessity of providing for -them, and also in order that the parents may have opportunity to rest -and renew their plumage before starting for winter quarters. The -young birds are therefore likely to drift together and, having no further -responsibility, may start south ahead of their parents. In contrast with -this indifference on the part of the adults of perching birds, Canada -geese and some others remain in family groups, the parent birds undergoing -the wing molt that renders them flightless during the period of -growth of their young, so that old and young acquire their full plumage -at the same time and are able to start south together. The large flocks, -therefore, are composed of many families that band together, and -when they separate into <b>V</b>-shaped units it is probably correct to assume -<span class="pagenum" id="Page_33">-33-</span> -that it is an old bird that leads the group. Where there is segregation -of the sexes, the young birds usually accompany their mothers, as is -the case with some of the ducks. After the females start to incubate -their eggs, the males of most species of ducks flock by themselves and -remain together until fall.</p> - -<p>The males and females of some species may migrate either simultaneously -or separately. In the latter case it is usually the males that -arrive first, sometimes great flocks of male birds, as in the red-winged -blackbird, reaching a locality several days before any of the females. -This is particularly the rule in spring: The first robins are usually found -to be males, as are also the first song sparrows, rose-breasted grosbeaks, -and scarlet tanagers. This early arrival of the males has been explained -on the theory of territorial possession, under which the male -selects the area where it elects to breed, each individual attempting to -protect a definite territory from trespass by other males of his own kind, -at the same time singing or otherwise announcing his presence and -inviting the later arriving female to examine the territory that he has -selected for nesting. The long-billed marsh wren is a noteworthy -example, and the males of this species may enthusiastically build several -dummy nests before the females arrive.</p> - -<p>In a few species the males and females apparently arrive at the breeding -grounds together and proceed at once to nest building. In fact -among the shore birds, ducks, and geese, courtship and mating may -take place in whole or in part while the birds are in the South or on -their way north, so that when they arrive at the northern nesting -grounds they are paired and ready to proceed at once with the raising -of their families. Mallards and black ducks may be observed in pairs -as early as January, the female leading and the male following when -they take flight. Naturally these mated pairs migrate north in company, -and it was largely to protect such species that duck shooting in -spring was abolished by Federal law a number of years ago.</p> - -<p>Many shore birds nest well within the Arctic Circle, and it is the opinion -of ornithologists that most of these birds share, at least in part, the -habits of the phalaropes, a family in which the male assumes the entire -care of the eggs and young. If this be true, it explains why in southern -latitudes so many of the earliest fall arrivals are females that may have -deserted the breeding grounds after the eggs were laid.</p> - -<p>Migratory flights are frequently accomplished in close flock formation, -as with the shore birds, blackbirds, and waxwings, and especially -<span class="pagenum" id="Page_34">-34-</span> -some of the sparrows—the snow buntings, longspurs, juncos, and tree -sparrows. Other species, however, though they travel in flocks, maintain -a very loose formation; examples are the turkey vultures, the -hawks, swifts, blue jays, swallows, warblers, and bluebirds. Still -others, the grebes, great horned owls, winter wrens, shrikes, and belted -kingfishers for example, ordinarily travel alone and when several are -found in close proximity it is an indication that they have been drawn -together by unusual conditions, such as abundant food.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Where_Birds_Migrate"><i>Where Birds Migrate</i></h2> -</div> - - -<p>Definite evidence shows that both the length and the duration of -the migratory journey vary greatly. The bobwhite and the western -quails, the cardinal, the Carolina wren, and probably some of the titmice -and woodpeckers, which are apparently almost or quite nonmigratory, -may round out their full period of existence without at any -time going more than 10 miles from the nest where they were hatched.</p> - - -<h3 id="Short">Short and undetermined migrations</h3> - -<p>Song sparrows, meadow larks, blue jays, and some other species -make such short migrations that the movement is difficult to detect, -as individuals may be found in one area throughout the year. Thus, -at the southern part of the range there is merely a concentration in -winter, the summer individuals being entirely sedentary. Speculation -is useless on the distances of individual migration without definite evidence -concerning the precise winter quarters of birds that summer in -a particular part of the breeding range of the species, but from the -records of banded birds important evidence is becoming available. -Eventually it may be possible to say definitely just how far the song -sparrows that nest in northern New England and the Maritime Provinces -of Canada travel to their winter quarters, and whether the blue -jays of New York and the upper Mississippi Valley remain throughout -the winter in their breeding areas, or move farther south and relinquish -their places to individuals from southern Canada.</p> - -<p>An illustration of what is now known on this subject is found in the -case of the robin. This bird occurs in the Middle Atlantic States -throughout the year, in Canada only in summer, and along the Gulf -coast only as a winter resident. On the Atlantic coast its movements -are readily ascertained, since, for example, in the section about Washington, -<span class="pagenum" id="Page_35">-35-</span> -D. C., the breeding robin is the southern variety (<i>Turdus -migratorius archrusterus</i>) which is found there from the first of April to -the last of October, when its place is taken (in smaller numbers) by the -northern robin (<i>Turdus migratorius migratorius</i>), which arrives about -the middle of October and remains until the following April. It is -probable that a similar interchange of individual robins occurs -throughout a large part of the balance of its range, the hardy birds from -the north being the winter tenants in the abandoned summer homes of -the southern birds.</p> - -<p>The red-winged blackbirds that nest in northern Texas are almost -sedentary, but in winter they are joined by representatives of other -subspecies that nest as far north as the Mackenzie Valley.</p> - - -<h3 id="Variable">Variable migrations within species</h3> - -<p>The difference in characters between subspecies has been used by -students of migration to discover other interesting facts concerning -variations of the migratory flight between closely related birds that -breed in different latitudes. The familiar eastern fox sparrow (<i>Passerella -iliaca iliaca</i>) breeds from northwestern Alaska to Labrador, and -in winter is found concentrated in the southeastern part of the United -States. It thus travels a long distance each year. On the west coast -of the continent, however, six subspecies of this bird breed in rather -sharply delimited ranges, extending from the region of Puget Sound -and Vancouver Island to Unimak Island, at the end of the Alaskan -Peninsula. One of these, known as the sooty fox sparrow (<i>P. i. fuliginosa</i>) -breeds in the Puget Sound area and makes practically no migration -at all, while the other races, nesting on the coast of British Columbia -and Alaska, are found in winter chiefly in California. The races -that breed farthest north are in winter found farthest south, illustrating -a tendency for those birds that are forced to migrate to pass over those -so favorably located that they have no need to leave their breeding areas, -while the northern birds settle for the winter in the unoccupied areas -farther south (<a href="#fig7">fig. 7</a>).</p> - -<p>Another example of the same kind is the Maryland yellowthroat of -the Atlantic coast. Birds occupying the most southern part of the -general range are almost nonmigratory, residing throughout the year -in Florida, while those breeding as far north as Newfoundland go to -the West Indies for the winter, thus passing directly over the home of -their southern relatives.</p> - -<p><span class="pagenum" id="Page_36">-36-</span></p> - -<div class="figcenter" id="fig7" style="width: 476px;"> - <img class="w100" src="images/fig7.png" width="476" height="641" alt="" /> - <div class="caption"><i>Figure 7.</i>—Migration of Pacific-coast forms of the fox sparrow. The -breeding ranges of the different races are encircled by solid lines, -while the winter ranges are dotted. The numbers indicate the areas -used by the different subspecies, as follows: 1. Shumagin fox sparrow; -2. Kodiak fox sparrow; 3. Valdez fox sparrow; 4. Yakutat fox -sparrow; 5. Townsend fox sparrow; 6. Sooty fox sparrow (After -Swarth, courtesy of the Museum of Vertebrate Zoology, University -of California).</div> -</div> - -<p><span class="pagenum" id="Page_37">-37-</span></p> - -<p>The palm warbler (<i>Dendroica palmarum</i>) which breeds from Nova -Scotia and Maine west and northwest to southern Mackenzie, has been -separated into two subspecies. Those breeding in the interior of -Canada (<i>D. p. palmarum</i>) make a 3,000-mile journey from Great -Slave Lake to Cuba, passing through the Gulf States early in October. -After the bulk have passed, the palm warblers from the Northeastern -States and Provinces (<i>D. p. hypochrysea</i>) drift slowly into the Gulf -Coast region, where they remain for the winter. Their migratory -journey is about half as long as that of the northwestern subspecies.</p> - -<p>There is no invariable law governing the distance of migration, although -in general it is found that where a species has an extensive -range, the subspecies that breed farthest north go farthest south to -spend the winter.</p> - - -<h3 id="Fall_flights">Fall flights not far south of breeding ranges</h3> - -<p>Some other species that have extensive summer ranges, for instance -the pine warbler, rock wren, field sparrow, loggerhead shrike, and -black-headed grosbeak, are found to concentrate during the winter -season in the southern part of the breeding range, or to occupy additional -territory that is only a short distance farther south. The entire -species may thus be confined within a restricted area for the period of -winter, and then, with the return of warmer weather, spreads out to -reoccupy the full range.</p> - -<p>There are many species, including the tree sparrow, slate-colored -junco, and Lapland longspur, that nest in Canada and winter in the -United States; while others, including the vesper sparrow, chipping -sparrow, grackles, red-winged blackbirds, bluebirds, the woodcock, -and several species of ducks, nest in the northern United States and -move south for the winter to areas along the Gulf of Mexico. This list -includes the more hardy species, some individuals of which may linger -in protected places well within the reach of severe cold, as, for example, -Wilson's snipe or jacksnipe, which frequently is found during subzero -weather in parts of the Rocky Mountain region where warm springs -assure a food supply. More than 100 of our summer birds leave the -United States entirely and spend the winter in the West Indies, or in -Central America or South America. For example, the Cape May -warbler, which breeds from northern New England, northern Michigan, -and northern Minnesota, north to New Brunswick, Nova Scotia, -<span class="pagenum" id="Page_38">-38-</span> -and nearly to Great Slave Lake, is concentrated in winter chiefly in the -West Indies, its metropolis at this season being the island of Hispaniola.</p> - - -<h3 id="Long_distance">Long-distance migrations</h3> - -<p>Some of the common summer residents are not content with a trip -to northern South America, but push on across the Equator and finally -come to rest for the winter in the pampas of Argentina, or even in -Patagonia. Thus some species that are more or less associated with -each other in summer, as nighthawks, barn swallows, cliff swallows, -and some of the thrushes, may also occupy the same general winter -quarters in Brazil. Some individual nighthawks and barn swallows -travel still farther, and of all North American land birds these species -probably have the longest migration route, as they occur north in summer -to Yukon and Alaska, and south in winter to Argentina, 7,000 -miles away. Such seasonal flights are exceeded in length, however, -by the journeys of several species of water birds, chiefly members of -the suborder of shore birds. In this group there are 19 species that -breed north of the Arctic Circle and winter in South America, 6 of them -going as far south as Patagonia, and thus having a migration route -more than 8,000 miles in length.</p> - -<p>The arctic tern is the champion "globe trotter" and long-distance flier -(<a href="#fig8">fig. 8</a>). Its name "arctic" is well earned, as its breeding range is circumpolar -and it nests as far north as it can find a suitable place. The -first nest to be found in this region was only 7½ degrees from the -North Pole, and it contained a downy chick surrounded by a wall of -newly fallen snow that had been scooped out by the parent. In North -America the arctic tern breeds south in the interior to Great Slave Lake, -and on the Atlantic coast to Massachusetts. After the young are grown -the arctic terns disappear from their North American breeding -grounds, and a few months later they may be found in the Antarctic -region, 11,000 miles away. Until very recently the route followed by -these hardy fliers was a complete mystery, for although a few scattered -individuals have been noted south as far as Long Island, the species is -otherwise practically unknown along the Atlantic coasts of North -America and South America. It is, however, known as a migrant on -the west coast of Europe and Africa. By means of numbered bands -the picture is now developing of what is apparently not only the longest -but also one of the most remarkable of all migratory journeys.</p> - -<p><span class="pagenum" id="Page_39">-39-</span></p> - -<div class="figcenter" id="fig8" style="width: 482px;"> - <img class="w100" src="images/fig8.png" width="482" height="646" alt="" /> - <div class="caption"><i>Figure 8.</i>—Distribution and migration of the arctic terns of eastern North -America. The route indicated for this bird is unique, as no other -species is known to breed abundantly in North America and to cross -the Atlantic Ocean to and from the Old World. The extreme summer -and winter homes are 11,000 miles apart, and as the route taken is -circuitous, these terns probably fly at least 25,000 miles each year.</div> -</div> - -<p><span class="pagenum" id="Page_40">-40-</span></p> - -<p>Judging by the evidence at present available it seems likely that the -arctic terns of eastern North America originally found their way here -from the Old World, probably by way of Iceland and Greenland. -Consequently when the time comes for them to migrate to winter -quarters they do not go directly south as do the common and Forster's -terns, but instead they fly back eastward along their ancestral route -across the Atlantic to the shores of Europe and then go south along -the African coast to their winter home. Those that breed in the northwestern -part of the continent, as in Alaska, probably migrate chiefly -down the western coast, as the species is not infrequently reported on -the coast of California and also on the western coast of South America.</p> - -<p>The evidence yielded by banding consists of only six definite cases, -but their interpretation permits but one conclusion. All were banded -either as downy chicks or as nonflying immature birds. The details -of their banding and recovery are of sufficient interest to justify citing -in detail. The first was banded on July 3, 1913, at Eastern Egg Rock, -Maine,<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">[2]</a> and in August 1917 was found dead in the Niger River delta, -West Africa. The second was banded at the Red Islands, Turnevik -Bay, Labrador, on July 22, 1927, and was recovered near La Rochelle, -France, on October 1, 1927. The third, also banded on the Red Islands, -on July 23, 1928, was retaken at Margate, near Port Shepstone, Natal, -South Africa, on November 14, 1928. The fourth, banded at Machias -Seal Island, New Brunswick, on July 20, 1935, was captured near St. -Nazaire, France, October 8, 1935. The fifth and sixth were banded at -Machias Seal Island also; the fifth, banded July 5, 1947, was found on -November 10, 1948, at Kingfisher Creek, Sedgefield, near Wilderness, -Eastern Cape Province, South Africa, while the sixth, banded on July -18, 1948, was picked up dead during the latter part of September 1948 -on the hills near Kyle Strome, Sutherland, Scotland. All that remained -of the bird that provides the last-named case was a mutilated -foot and it appeared that it had been the victim of some predator. It -should be pointed out that the flights indicated in the third and fifth -cases detailed above, are the longest known for any birds. Both are -between 8,000 and 9,000 miles, which in the case of No. 3 was accomplished -in less than 3 months.</p> - -<div class="footnote"> - -<p><a id="Footnote_2" href="#FNanchor_2" class="label">[2]</a> Recorded at the time of banding as a common tern, a natural -error, as the downy young of common and arctic terns look almost exactly -alike.</p> - -</div> - -<p>Probably no other animal in the world enjoys as many hours of -daylight as does the arctic tern, since for these birds the sun never sets -<span class="pagenum" id="Page_41">-41-</span> -during the nesting season in the northern part of the range, while -during their sojourn in the south, daylight is continuous. During -several months of the year they have 24 hours of daylight and during -the other months considerably more daylight than darkness.</p> - - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Routes_of_Migration"><i>Routes of Migration</i></h2> -</div> - - -<p>While it is beyond question that certain general directions of flight -are constantly followed by migratory birds, it is well to remember that -the term "migration route" is to some extent a theoretical concept concerned -entirely with the lines of general advance or retreat of a species, -rather than the exact course followed by individual birds. Even the -records of banded birds usually show no more than the place of banding -and recovery, and one must have recourse to intermediate records -and to reasoning based on probabilities to fill in details of the route -actually traversed between the two points.</p> - -<p>There is also infinite variety in the routes covered during migration -by different species. In fact, the choice of migration highways is so -wide that it seems as if the routes of no two species coincide. Differences -in distance traveled, time of starting, speed of flight, geographical -position, latitudes of breeding and of wintering grounds, and in other -factors, all contribute to this great variation of migration routes. -Nevertheless, there are certain factors that serve to guide the avian -travelers along more or less definite lines, and it is possible to define -general lines of migration for the majority of species.</p> - -<p>It has been frequently observed that migrating birds have a tendency -to follow major topographic lines on the earth's surface when -their trend is in the general direction of the birds' journey. Bird -migration is generally thought of as a north-and-south movement, -with the lanes of heavier concentration following the coasts, mountain -ranges, and principal river valleys. To a considerable extent this is -the case, particularly in North America, where the coast lines, mountain -chains, and larger rivers in general run north and south. In cases -where the migration is a long one, however, the notion must be abandoned -that the birds' flight is always restricted to narrow routes that -follow river valleys and the like, as many species seem to disregard -utterly such apparently good natural highways. For example, the -Arkansas River has a general east-and-west course for a great part of -its length, and while it does constitute a route for many perching birds -en route from the Mississippi Valley to the Rocky Mountain region, -<span class="pagenum" id="Page_42">-42-</span> -some of the hawks and many ducks and shore birds pay the valley scant -attention. They may arrest the autumn journey to feed among the -cottonwoods or along sand bars, but when ready to resume their flight -they leave the river and fly directly south over the more or less arid -region that lies between the Arkansas and the Rio Grande.</p> - - -<h3 id="migration_lanes" class="caption3">Wide and narrow migration lanes</h3> - -<p>When birds start their southward migration the movement necessarily -involves the full width of the breeding range. Later there is -a convergence of the lines of flight taken by individual birds, owing -to the conformation of the land mass, and as the species proceeds -southward the width of the occupied region becomes less and less. -An example of this is provided by the common kingbird, which breeds -from Newfoundland to British Columbia, a summer range 2,800 miles -wide. On migration, however, its paths converge until in the southern -part of the United States the occupied area extends from Florida to the -mouth of the Rio Grande, a distance of only 900 miles, and still farther -south the migration path is further restricted. In the latitude of Yucatan -it is not more than 400 miles wide, and it is probable that the great -bulk of the species moves in a belt that is less than half that width.</p> - -<p>A migration route, therefore, may be anything from a narrow path -that adheres closely to some definite geographical feature, such as a -river valley or a coast line, to a broad boulevard that leads in the desired -direction and which follows only the general trend of the land -mass. Also it is to be remembered that whatever main routes are -described, there remains a multitude of tributary and separate minor -routes. In fact, with the entire continent of North America crossed -by migratory birds, the different groups or species frequently follow -lines that may repeatedly intersect those taken by others of their own -kind or by other species. The arterial routes, therefore, must be considered -merely as indicating paths of migration on which the tendency -to concentrate is particularly noticeable.</p> - -<p>In considering the width of migration lanes it will be obvious that -certain species, as the knot and the purple sandpiper, which are normally -found only along the coasts, must have extremely narrow routes -of travel. They are limited on one side by the broad waters of the -ocean, and on the other by land and fresh water, both of which are -unsuited to furnish the food that is desired and necessary to the well-being -of these species.</p> - -<p><span class="pagenum" id="Page_43">-43-</span></p> - -<div class="figcenter" id="fig9" style="width: 468px;"> - <img class="w100" src="images/fig9.png" width="468" height="432" alt="" /> - <div class="caption"><i>Figure 9.</i>—Breeding and wintering ranges and migration of Harris's -sparrow, an example of a narrow migration route through the interior -of the country. The heavy broken lines enclose the region traversed -by the majority of these finches; the light broken line encloses the -country where they occur with more or less regularity; while the spots -indicate records of accidental or sporadic occurrence.</div> -</div> - -<p>Among land birds that have a definite migration, the Ipswich sparrow -has what is probably the most restricted migration range of any -species. It is known to breed only on Sable Island, Nova Scotia, and it -winters along the Atlantic coast south to Georgia. Living constantly -within sound of the surf, it is rarely more than a quarter of a mile -from the outer beach, and is entirely at home among the sand dunes -and their sparse covering of coarse grass.</p> - -<p><span class="pagenum" id="Page_44">-44-</span></p> - -<div class="figcenter" id="fig10" style="width: 473px;"> - <img class="w100" src="images/fig10.png" width="473" height="585" alt="" /> - <div class="caption"><i>Figure 10.</i>—Distribution and migration of the scarlet tanager. During -the breeding season individual scarlet tanagers may be 1,900 miles -apart in an east-and-west line across the breeding range. In migration, -however, the lines converge until in southern Central America -they are not more than 100 miles apart. For migration paths of -other widths see figures 9, 11, and 12.</div> -</div> - -<p>Harris's sparrow supplies an interesting example of a narrow migration -route in the interior of the country (<a href="#fig9">fig. 9.</a>) This fine, large finch -is known to breed only in the region from Churchill, on the west shore -of Hudson Bay, northwest to the shores of Great Bear Lake. Very -few actual breeding records of the species are available, but these are -sufficient to indicate that the breeding range is in the strip of country -characterized by more or less stunted timber just south of the limit of -trees. When it begins its fall migration, this species necessarily covers -the full width of its breeding area. Then it proceeds almost directly -<span class="pagenum" id="Page_45">-45-</span> -south, or slightly southeasterly, the area covered by the majority of the -birds becoming gradually constricted, so that by the time it reaches the -United States it is most numerous in a belt about 500 miles wide, extending -across North Dakota to central Minnesota. Harris's sparrows -are noted on migration with fair regularity east to the western shore -of Lake Michigan, and west to the foothills of the Rocky Mountains, -but the great bulk of the species moves north and south through a -relatively narrow path in the central part of the continent. Present -knowledge suggests that the reason for this narrow migration range -is the close association that Harris's sparrow maintains with a certain -type of habitat' including brushy places, thickets, edges of groves, and -weed patches. While these environmental conditions are found in -other parts of the country, the region crossed by this sparrow presents -almost a continuous succession of habitat of this type. Its winter -range extends from southeastern Nebraska and northwestern Missouri, -across eastern Kansas and Oklahoma and through a narrow section of -central Texas, at places hardly more than 150 miles wide.</p> - -<p>The scarlet tanager presents another extreme case of narrowness of -migration route (<a href="#fig10">fig. 10</a>), its breeding range extending in greatest width -from New Brunswick to Saskatchewan, a distance of about 1,900 miles. -As the birds move southward in fall their path of migration becomes -more and more constricted, until at the time they leave the United -States all are included in the 600-mile belt from eastern Texas to the -Florida peninsula. Continuing to converge through Honduras and -Costa Rica, the boundaries there are not more than 100 miles apart. -The species winters in northwestern South America, where it spreads -out over most of Colombia, Ecuador, and Peru.</p> - -<p>The rose-breasted grosbeak also leaves the United States through -the 600-mile stretch from eastern Texas to Apalachicola Bay, but -thereafter the lines do not further converge, as this grosbeak enters -the northern part of its winter quarters in Central America and South -America through a door of about the same width (<a href="#fig11">fig. 11</a>).</p> - -<p>Although the cases cited represent extremes of convergence, a narrowing -of the migratory path is the rule to a greater or less degree for the -majority of North American birds. The shape of the continent tends -to effect this, and so the width of the migration route in the latitude of -the Gulf of Mexico is usually much less than in the breeding territory.</p> - -<p>The redstart represents a notable case of a wide migration route, -although even in the southern United States this is much narrower than -<span class="pagenum" id="Page_46">-46-</span> -the breeding range (<a href="#fig12">fig. 12</a>). These birds, however, cross all parts of -the Gulf of Mexico and pass from Florida to Cuba and Haiti by way of -the Bahamas, so that here their route has a width of about 2,500 miles.</p> - -<div class="figcenter" id="fig11" style="width: 472px;"> - <img class="w100" src="images/fig11.png" width="472" height="548" alt="" /> - <div class="caption"><i>Figure 11.</i>—Distribution and migration of the rose-breasted grosbeak. -Though the width of the breeding range is about 2,500 miles, the -migratory lines converge until the boundaries are only about 700 -miles apart when the birds leave the United States. For migration -paths of other widths see figures 9, 10, and 12.</div> -</div> - - -<h3 id="The_flyways">The flyways</h3> - -<p>In 1935, as a result of studies of banding data, the author discovered -the existence of the four great flyway systems. This discovery, based -<span class="pagenum" id="Page_47">-47-</span> -upon analyses of the several thousand records of the recovery of migratory -waterfowl then available, was announced by the Biological Survey -(Lincoln, 1935c) and, beginning in 1948, it has served as the basis for -administrative action by the Fish and Wildlife Service in the annual -hunting regulations.</p> - -<div class="figcenter" id="fig12" style="width: 477px;"> - <img class="w100" src="images/fig12.png" width="477" height="547" alt="" /> - <div class="caption"><i>Figure 12.</i>—Distribution and migration of the redstart. An example -of a wide migration route, since birds of this species cross all parts -of the Gulf of Mexico, or may travel from Florida to Cuba and through -the Bahamas. Their route thus has an east-and-west width of more -than 2,000 miles. For migration paths of greater or less extent see -figures 9, 10, and 11.</div> -</div> - -<p>Although this study was confined to this one family of birds there -is a growing mass of evidence in support of the belief that all populations -<span class="pagenum" id="Page_48">-48-</span> -of migratory birds adhere with more or less fidelity to their respective -flyways. The terms "flyway" and "migration route" have in -the past been used more or less as synonyms but the modern concept -of a flyway is that it is a vast geographic region with extensive breeding -grounds and wintering grounds connected with each other by a more -or less complicated system of migration routes. Each flyway has its -own populations of birds, even of those species that may have a continental -distribution. The breeding grounds of one or more flyways -may (and usually do) overlap broadly, so that during the nesting -season extensive areas may be occupied by birds of the same species but -which belong to different flyways.</p> - -<p>The maps (figs. 13, 14, 15, and 16) show the flyways as they are now -understood. It should be pointed out, however, that in the other maps -used in this bulletin, the entire range of a species is shown without -any attempt to distinguish by flyways the different populations. As -banding data accumulate for the nongame species, this distinction will -ultimately be possible, but for the time being, consideration of their -migrations must be chiefly by routes.</p> - -<p>The following discussion of the principal routes of North American -birds relates chiefly to the fall migration, for, except as otherwise noted, -the spring flight generally retraces the same course. The routes indicated -on the map (<a href="#fig17">fig. 17</a>) must not be considered as representing paths -with clearly defined borders, but rather as convenient subdivisions of -the four great flyways that, as indicated above, cover practically the -entire width of the North American Continent and extend from the -Arctic coast to South America.</p> - -<p><span class="pagenum" id="Page_49">-49-</span></p> - -<div class="figcenter" id="fig13" style="width: 476px;"> - <img class="w100" src="images/fig13.png" width="476" height="649" alt="" /> - <div class="caption"><i>Figure 13.</i>—The Atlantic flyway.</div> -</div> - - -<h3 id="Atlantic_oceanic_route">Atlantic oceanic route</h3> - -<p>By reference to <a href="#fig17">figure 17</a> it will be noted that route No. 1 is almost -entirely oceanic, passing directly over the Atlantic Ocean from Labrador -and Nova Scotia to the Lesser Antilles, and then through this group -of small islands to the mainland of South America. This is not a -popular route and its chief claim to fame is that it is the fall route -used by most of the adult eastern golden plovers, and probably by some -other shore birds. Since it lies entirely over the sea, this route is definitely -known only at its terminals and from occasional observations -made on Bermuda and other islands in its course. Some of the shore -birds that breed on the Arctic tundra of Mackenzie and Alaska fly -southeastward across Canada to the Atlantic coast and finally follow this -<span class="pagenum" id="Page_50">-50-</span> -oceanic route to the mainland of South America. The golden plover -may accomplish the whole 2,400 miles without pause or rest, in fair -weather the flocks passing Bermuda and sometimes even the islands -of the Antilles without stopping. Although most birds make their -migratory flights either by day or by night, the golden plover in this -remarkable journey flies both day and night. As it swims lightly -and easily it may make a few short stops along the way, and it has -been seen actually resting on the ocean. Other shore birds have been -observed busily feeding in the great area of ocean known as the Sargasso -Sea, where thousands of square miles of floating seaweed teem -with marine life.</p> - -<div class="figcenter" id="fig14" style="width: 479px;"> - <img class="w100" src="images/fig14.png" width="479" height="630" alt="" /> - <div class="caption"><i>Figure 14.</i>—The Mississippi flyway.</div> -</div> - -<p><span class="pagenum" id="Page_51">-51-</span></p> - -<div class="figcenter" id="fig15" style="width: 489px;"> - <img class="w100" src="images/fig15.png" width="489" height="648" alt="" /> - <div class="caption"><i>Figure 15.</i>—The Central flyway.</div> -</div> - -<div class="figcenter" id="fig16" style="width: 480px;"> - <img class="w100" src="images/fig16.png" width="480" height="618" alt="" /> - <div class="caption"><i>Figure 16.</i>—The Pacific flyway.</div> -</div> - -<p>The annual flight of the adult eastern golden plover is so wonderful -that it may be given in some detail, particularly since it is one of the -exceptions to the general rule that spring and fall movements are over -the same routes (<a href="#fig18">fig. 18</a>). After reaching the South American coast -the birds make a short stop and then continue overland to the pampas -<span class="pagenum" id="Page_52">-52-</span> -of Argentina, where they remain from September to March. Leaving -their winter quarters, they cross northwestern South America and the -Gulf of Mexico, reaching the North American mainland on the coasts -of Texas and Louisiana. Thence they proceed slowly up the Mississippi -Valley, and by the early part of June are again on their breeding -grounds, having performed a round-trip journey in the form of an -<span class="pagenum" id="Page_53">-53-</span> -enormous ellipse with the minor axis about 2,000 miles and the major -axis 8,000 miles, reaching from the Arctic tundra to the pampas of -Argentina. The older birds are probably accompanied by some of -the young, perhaps those from early nestings, but most of the immature -birds leave their natal grounds late in summer and move southward -through the interior of the country, returning in spring over essentially -the same course. The elliptical route is therefore used chiefly by -fully adult birds.</p> - -<div class="figcenter" id="fig17" style="width: 474px;"> - <img class="w100" src="images/fig17.png" width="474" height="390" alt="" /> - <div class="caption"><i>Figure 17.</i>—Principal migration routes used by birds in passing from -North America to winter quarters in the West Indies, Central America, -and South America. Route No. 4 is the one used most extensively; -only a few species make the 2,400-mile flight from Nova Scotia to -South America.</div> -</div> - -<p><span class="pagenum" id="Page_54">-54-</span></p> - -<div class="figcenter" id="fig18" style="width: 474px;"> - <img class="w100" src="images/fig18.png" width="474" height="633" alt="" /> - <div class="caption"><i>Figure 18.</i>—Distribution and migration of the golden plover. Adults -of the eastern form migrate across northeastern Canada and then by -a nonstop flight reach South America. In spring they return by way -of the Mississippi Valley. Their entire route is therefore in the form -of a great ellipse with a major axis of 8,000 miles and a minor axis -of about 2,000 miles. The Pacific golden plover, which breeds in -Alaska, apparently makes a nonstop flight across the ocean to -Hawaii, the Marquesas Islands, and the Low Archipelago, returning -in spring over the same route.</div> -</div> - -<p><span class="pagenum" id="Page_55">-55-</span></p> - - -<h3 id="Atlantic_coast_route">Atlantic coast route and tributaries</h3> - -<p>The Atlantic coast is a regular avenue of travel, and along it are -many famous points for observing both land and water birds. About -50 different kinds of land birds that breed in New England follow the -coast southward to Florida and travel thence by island and mainland -to South America (<a href="#fig17">fig. 17</a>, route 2). As will be seen from the map, -a seemingly natural and convenient highway extends through the -Bahamas, Cuba, Hispaniola, Puerto Rico, and the Lesser Antilles to the -South American coast. Resting places are afforded at convenient intervals, -and at no time need the aerial travelers be out of sight of land. It -is not, however, the favored highway, and only about 25 species of -birds go beyond Cuba to Puerto Rico along this route to their winter -quarters, while only 6 species are known to reach South America by -way of the Lesser Antilles. The obvious draw-back is lack of adequate -food. The total area of all the West Indies east of Puerto Rico is less -than that of Rhode Island, so that if only a small part of the birds of -the eastern United States were to travel this way, it is doubtful whether -even the luxuriant flora and fauna of tropical habitats would provide -food sufficient for their needs. Nevertheless, many thousands of -coots, widgeons, pintails, blue-winged teal, and other waterfowl and -shorebirds regularly spend the winter season in the coastal marshes -and the inland lakes and ponds of Cuba, Hispaniola, and Puerto Rico.</p> - -<p>The map (<a href="#fig17">fig. 17</a>) also will show that route No. 3 presents a direct -line of travel for Atlantic coast migrants en route to South America, -although it involves much longer flights. It is used almost entirely -by land birds. After taking off from the coast of Florida there are -only two intermediate land masses where the migrants may pause for -rest and food. Nevertheless, tens of thousands of birds of some 60 -species cross the 150 miles from Florida to Cuba where about half this -number elect to remain for the winter months. The others do not -hesitate to fly the 90 miles between Cuba and Jamaica, but from that -point to the South American coast there is a stretch of islandless ocean -fully 500 miles across. Scarcely a third of the North American -migrants leave the forested mountains of Jamaica to risk the perils of -this ocean trip. Chief among these is the bobolink, which so far outnumbers -all other birds using this route that it may be well called the -"bobolink route" (<a href="#fig19">fig. 19</a>). As traveling companions along this route, -the bobolink may meet a vireo, a kingbird, and a nighthawk from -Florida; the chuck-wills-widow of the Southeastern States; the black-billed -and the yellow-billed cuckoos from New England; the gray-cheeked -thrush from Quebec; bank swallows from Labrador; and -the blackpolled warbler from Alaska. Sometimes this scattered assemblage -will be joined by a tanager or a wood thrush but the "bobolink -route" is not popular with the greater number of migrants, and -although many individuals traverse it, they are only a small fraction -of the multitudes of North American birds that spend the winter -in South America.</p> - -<p><span class="pagenum" id="Page_56">-56-</span></p> - -<div class="figcenter" id="fig19" style="width: 477px;"> - <img class="w100" src="images/fig19.png" width="477" height="623" alt="" /> - <div class="caption"><i>Figure 19.</i>—Distribution and migration of the bobolink. In crossing to -South America most of the bobolinks use route 3 (<a href="#fig17">fig. 17</a>), showing -no hesitation in making the flight from Jamaica across an islandless -stretch of ocean. It will be noted that colonies of these birds have -established themselves in western areas, but in migration they adhere -to the ancestral flyways and show no tendency to take the short -cut across Arizona, New Mexico, and Texas. (<a href="#Page_55">See p. 55.</a>)</div> -</div> - -<p><span class="pagenum" id="Page_57">-57-</span></p> - -<p>Formerly it was thought that most of the North American land -birds that migrate to Central America made a leisurely trip along the -Florida coast, crossed to Cuba, and thence made the short flight from -the western tip of Cuba to Yucatan. A glance at the map would suggest -this as a most natural route, but as a matter of fact it is practically -deserted except for a few swallows and shorebirds, or an occasional -land bird storm-driven from its accustomed course. What actually -happens is that in the fall many of the birds that breed east of the -Allegheny Mountains travel parallel to the seacoast in a more or less -southwesterly direction and, apparently maintaining this same general -course from northwestern Florida, cross the Gulf of Mexico to the -coastal regions of eastern Mexico.</p> - -<p>The routes used by the Atlantic brant merit some detail for the reason -that these were long misunderstood. These birds winter on the Atlantic -coast, chiefly at Barnegat Bay, N. J., but (depending upon the -severity of the season and the food available) south also to North Carolina. -Their breeding grounds are in the Canadian arctic archipelago -and on the coasts of Greenland. According to the careful studies of -Lewis (1937), the main body travels northward in spring along the -coast to the Bay of Fundy, hence overland to Northumberland Strait, -which separates Prince Edward Island from the mainland of New -Brunswick and Nova Scotia. A minor route appears to lead northward -from Long Island Sound by way of such valleys as those of the Housatonic -and Connecticut Rivers, and on across southern Quebec to the -St. Lawrence River.</p> - -<p>After spending the entire month of May feeding and resting in -various parts of the Gulf of St. Lawrence, the eastern segment of the -brant population suddenly resumes its journey by crossing to the north -shore of the St. Lawrence estuary. The Bay of Seven Islands, in this -general region, is the point of departure for long overland flights that -are made by the two segments of the population. The eastern and -larger of these appears to fly almost due north to Ungava Bay and -from there to nesting grounds, probably in Baffin Island and Greenland. -The smaller segment travels a route that is but slightly north -of west to the southeastern shores of James Bay, although somewhere -<span class="pagenum" id="Page_58">-58-</span> -to the east of that area some of the flocks take a more northwesterly -course, descending the Fort George River to reach the eastern shore -of James Bay about two-thirds of the distance north of its southern -extremity. Upon their arrival at either of these two points on James -Bay, the brant of this western segment turn northward and proceed -through the eastern part of Hudson Bay to their breeding grounds, -probably in western Baffin Island, Southampton Island, and other -islands in the Canadian Arctic.</p> - -<p>In general, the fall migration of the brant follows the routes utilized -in the spring. At this season, when gathering for the flight of 570 -miles to the St. Lawrence River, they appear only on the western and -southern shores of Ungava Bay. Also, it appears that most of the birds -of the western segment, instead of following the eastern shores of -Hudson and James Bays, turn southwestward across the former, by -way of the Belcher Islands, to Cape Henrietta Maria and from there -south along the western shores of James Bay by way of Akimiski and -Charlton Islands. At the southern end of James Bay they are joined -by those that have taken the more direct route along the east coasts -of the bays and all then fly overland 570 miles to the estuary of the St. -Lawrence River.</p> - -<p>The Atlantic flyway receives accretions of waterfowl from three or -four interior migration paths, one of which is of first importance, as -it includes great flocks of canvasbacks, redheads, scaup ducks, Canada -geese, and many of the black ducks that winter in the waters and -marshes of the coastal region south of Delaware Bay. The canvasbacks, -redheads, and scaups come from their breeding grounds on the -great northern plains of central Canada, follow the general southeasterly -trend of the Great Lakes, cross Pennsylvania over the mountains, -and reach the Atlantic coast in the vicinity of Delaware and Chesapeake -Bays. Black ducks, mallards, and blue-winged teals that have gathered -in southern Ontario during the fall leave these feeding grounds -and proceed southwest over a course that is apparently headed for the -Mississippi Valley. Many do continue this route down the Ohio -Valley, but others, upon reaching the vicinity of the St. Clair Flats, -between Michigan and Ontario, swing abruptly to the southeast and, -crossing the mountains in a single flight, reach the Atlantic coast south -of New Jersey. This route, with its Mississippi Valley branch, has -been fully demonstrated by the recovery records of ducks banded at -Lake Scugog, Ontario.</p> - -<p><span class="pagenum" id="Page_59">-59-</span></p> - -<p>The white-winged scoter, which also breeds in the interior of the -continent from northern North Dakota north to the Arctic coast, was -at one time credited with an elliptical migration route, at least insofar -as those wintering on the Atlantic coast are concerned. This sea duck -nests only near fresh water but spends the winters on the ocean along -both the Atlantic and Pacific coasts of the United States. It migrates -over land surfaces mainly at night and it is now believed that after -working northward to the waters of Long Island Sound it starts up -the valleys of the Hudson and Connecticut Rivers and flies overland -to the Great Lakes, from which region it continues west and northwest -to the breeding grounds, returning to its winter quarters over -the same route. Early ideas alleging an elliptical route probably arose -from the fact that great numbers of first-year nonbreeding birds regularly -pass up the New England coast, cross the Gulf of St. Lawrence -and spend the summer loafing off the coast of Labrador. In the fall -these birds form into large flocks and retrace their flight, chiefly during -daylight hours, to winter quarters from southeastern Maine south at -least to Chesapeake Bay. As it was not known that the white-winged -scoter does not usually breed until it is 2 years old, and since the southward -movement of yearling birds was conspicuous while the travels of -those from the nesting grounds were chiefly at night, the theory was -advanced that the latter flew 1,500 miles due east from the region west -of Hudson Bay to the coast of Labrador, thence southward to the known -winter quarters.</p> - -<p>A study of the Canada geese that winter abundantly in the waters -of Back Bay, Va., and Currituck Sound, N. C., reveals another important -tributary to the Atlantic coast route. Banding has shown -that the principal breeding grounds of these birds are among the islands -and on the eastern shore of Hudson Bay. From this region they move -south in autumn to the point of Lower Ontario between Lakes Erie -and Huron. Occasionally one of these geese will be recovered in the -Mississippi Valley but the great majority are retaken either on their -breeding grounds or on the Atlantic coast south of Delaware Bay, -showing another instance of a long cross-country flight by waterfowl. -Although the Canada goose is abundant in migration on the coast of -New England, the birds taken there rarely include any of those banded -in southern Ontario. The northeastern population of these geese -comes from breeding areas in New England, the Maritime Provinces -of Canada, Newfoundland, and the desolate coast of Labrador, their -<span class="pagenum" id="Page_60">-60-</span> -migration being entirely coastwise. Still another cross-country route -between the Mississippi Valley and the Atlantic coast remains to be -briefly described. It is not yet well understood, but the banding of -ducks such as the blue-winged teal on the coastal saw-grass marshes of -South Carolina has revealed that there is a migration route across the -Appalachians to the Mississippi Valley. Birds marked in these -marshes have been retaken in Tennessee and Kentucky, as well as in -other States farther north in the Mississippi Flyway.</p> - - -<h3 id="Mackenzie_Valley">Mackenzie Valley—Great Lakes—Mississippi Valley route -and tributaries</h3> - -<p>Easily the longest route of any in the Western Hemisphere is that -extending from the Mackenzie Valley past the Great Lakes and down -the Mississippi River, including its tributaries. Its northern terminus -is on the Arctic coast in the regions of Kotzebue Sound, Alaska, and -the mouth of the Mackenzie River, while its southern end lies in Patagonia. -During the spring migration some of the shore birds traverse -the full extent of this great path, and it seems likely that the nighthawk, -the barn swallow, the blackpolled warbler, and individuals of -several other species that breed north to Yukon and Alaska must twice -each year cover the larger part of it.</p> - -<p>For more than 3,000 miles—from the mouth of the Mackenzie to the -delta of the Mississippi—this route is uninterrupted by mountains. -In fact, there is not even a ridge of hills high enough to interfere with -the movements of the feathered travelers, and the greatest elevation -above sea level is less than 2,000 feet. Well timbered and watered, the -entire region affords ideal conditions for the support of its great hosts -of migrating birds. It is followed by such vast numbers of ducks, geese, -shore birds, blackbirds, sparrows, warblers, and thrushes, that observers -stationed at favorable points in the Mississippi Valley daring the height -of migration can see a greater number of species and individuals than -can be noted anywhere else in the world.</p> - -<p>Starting in the region of Kotzebue Sound, Alaska, the route extends -eastward across northern Alaska and joins another that has its origin -at the mouth of the Mackenzie River. The line of flight then trends -a little east of south through the great lake system of central Canada, -where it is joined by two or three other routes from the northeast that -have their origin on the central Arctic coast. Continuing southward -the migrating flocks are constantly augmented by additions to their -<span class="pagenum" id="Page_61">-61-</span> -numbers as they pass over the great breeding grounds of central and -southern Canada. Upon reaching the headwaters of the Missouri and -Mississippi Rivers the route follows these streams to the Gulf coast, -Arriving in this latitude many species, including the ducks and geese, -the robin, the myrtle warbler, and some others spread out east and west -for their winter sojourn. Others, despite the perils of a trip involving -a flight of several hundred miles across the Gulf of Mexico, strike out -boldly for Central America and South America. This part of the route -is a broad "boulevard" extending from northwestern Florida to eastern -Texas and reaching southward across the Gulf of Mexico to Yucatan -and the Isthmus of Tehuantepec (<a href="#fig17">fig. 17</a>, route 4). In other words, -when most of the birds (chiefly shore birds and land birds) that have -come south directly through the Mississippi Valley have reached the -coastal plains of Mississippi and Louisiana, they continue directly -across the Gulf of Mexico. This route appears to have preference over -the safer but more circuitous land or island routes by way of Texas -and Florida. During the height of migration some of the islands off -the coast of Louisiana are wonderful observation points for the student -of birds, as the feathered travelers literally swarm over them.</p> - -<p>Present detailed knowledge of the chief tributaries to the Mackenzie—Great -Lakes—Mississippi Valley highway relates chiefly to waterfowl. -Reference already has been made to the flight of the black ducks -(p. 58) that reach the Mississippi Valley from southern Ontario. Some -individuals of this species banded at Lake Scugog, Ontario, have been -recaptured in succeeding seasons in Wisconsin and Manitoba, but the -majority have been retaken at points south of the junction of the Ohio -River with the Mississippi, definitely indicating their route of travel -from southern Ontario.</p> - -<p>A second route that joins the main artery on its eastern side is the one -used by the blue goose, the migration route of which is probably more -nearly due north and south than that of any other North American -bird. The breeding grounds, which only in recent years have been -discovered, are mainly in the Fox Basin region of Baffin Island and -on Southampton Island. In fall these geese work southward, chiefly -along the eastern shore of Hudson Bay, and upon reaching the southern -extremity of James Bay they take off for what is practically a nonstop -flight to the great coastal marshes of Louisiana west of the delta of -the Mississippi River. In some seasons the flocks make intermediate -stops among the islands and sand bars of the Mississippi, as they are -<span class="pagenum" id="Page_62">-62-</span> -occasionally common in the general vicinity of Memphis, Tenn. Most -of the birds push on, however, and during the period from the first -of November to the last of March fully 90 percent of the species are -concentrated in the area between the Sabine and the Mississippi Rivers. -On the return trip northward there is sometimes a tendency for some of -the blue geese to veer off toward the northwest, as they are occasionally -abundant in eastern South Dakota and southeastern Manitoba. It is of -particular interest to note that while some other geese and many ducks -start their northward journey at the first sign of awakening spring, -the blue goose remains in its winter quarters until the season there is -far advanced, seemingly aware that its own breeding grounds in the -Arctic are still in the grip of winter.</p> - - -<h3 id="Great_Plains">Great Plains—Rocky Mountain routes</h3> - -<p>A great western highway also has its origin in the Mackenzie River -delta area and in Alaska. This is used chiefly by the pintail and the -American widgeon or baldpate, which fly southward through eastern -Alberta to western Montana. Some localities in this area, as for example, -the National Bison Range at Moiese, Mont., normally furnish -food in such abundance as to induce these birds to pause in their migratory -movement. Upon resuming travel, some flocks move almost -directly west across Idaho to the valley of the Columbia River, from -which they turn abruptly south to the interior valleys of California. -Others leave the Montana feeding and resting areas and turn southeastward -across Wyoming and Colorado to join the flocks that are moving -southward through the Great Plains (<a href="#fig15">fig. 15</a>).</p> - -<p>Many redheads that breed in the Bear River marshes in Utah take a -westerly route across Nevada to California, but some leave these breeding -grounds and fly northeastward across North Dakota and Minnesota -to join the flocks of these ducks that come out of the prairie regions -of Canada. A few of them even travel southeastward to the Atlantic -coast. This route can be traced by the records of ducks banded in summer -in the Bear River marshes and retaken the following fall at points -in eastern Montana, Wyoming, South Dakota, North Dakota, Minnesota, -Wisconsin, Michigan, Ohio, and Maryland. Great numbers, -however, follow another route from these marshes across the mountains -in an easterly direction, where it almost immediately turns southward -through Colorado and New Mexico, and continues to winter quarters -<span class="pagenum" id="Page_63">-63-</span> -in the Laguna Madre off the coast of Texas or in the Valley of Mexico -(<a href="#fig17">fig. 17</a>, route 6). This route also represents the travels of many of the -land birds of the Rocky Mountain region. Such birds perform comparatively -short migrations, most of them being content to stop when -they reach the middle districts of Mexico, only a few passing beyond -the southern part of that country.</p> - -<p>Observations made in the vicinity of Corpus Christi, Tex., have -shown one of the short cuts (<a href="#fig17">fig. 17</a>, route 5) that is, in effect, a part of -the great artery of migration. Thousands of birds pass along the -coast to the northern part of the State of Vera Cruz. As the coast of -the State of Tamaulipas to the north is arid and so entirely unsuited to -the needs of birds that are frequenters of moist woodlands, it is probable -that much or all of this part of the route is a short distance off shore. It -is used by such woodland species as the golden-winged warbler, the -worm-eating warbler, and the Kentucky warbler.</p> - - -<h3 id="Pacific_coast">Pacific coast route</h3> - -<p>Although it does present features of unusual interest, the Pacific -coast route is not of so great importance as some of the others described. -Because of the equable conditions that prevail, many species of birds -along the coast from the Northwestern States to southeastern Alaska -either do not migrate at all or else make relatively short journeys. This -route has its origin chiefly in Alaska, the general region of the delta -of the Yukon River marking its northern terminus, although a few -species join it after a flight westward along the Alaskan Arctic coast. -Some of the scoters and other sea ducks of the north Pacific region, -and the diminutive cackling goose which breeds in the delta of the -Yukon River, use the coastal sea route for all or most of their southward -flight. The journey of the cackling goose, as shown by return records -from birds banded at Hooper Bay, Alaska, has been traced southward -across the Alaska Peninsula and apparently across the Gulf of Alaska -to the Queen Charlotte Islands, the birds following the coast line south -to near the mouth of the Columbia River. There the route swings -toward the interior for a short distance before continuing south by -way of the Willamette River Valley. The winter quarters of the -cackling goose are chiefly in the vicinity of Tule Lake, on the Oregon-California -line, and in the Sacramento Valley of California, though a -few push on to the San Joaquin Valley.</p> - -<p><span class="pagenum" id="Page_64">-64-</span></p> - -<div class="figcenter" id="fig20" style="width: 476px;"> - <img class="w100" src="images/fig20.png" width="476" height="425" alt="" /> - <div class="caption"><i>Figure 20.</i>—The breeding range, winter range, and migration route of -Ross's goose. This is the only species of which all members apparently -breed in the Arctic regions, migrate south through the Mackenzie -Valley, and upon reaching the United States, turn to the southwest -rather than the southeast. The southern part of this route, -however, is followed by some mallards, pintails, baldpates, and -possibly by other ducks.</div> -</div> - -<p>A tributary of this flyway is followed by Ross's goose which is now -known to breed only in the Perry River district south of the Queen -Maud Gulf on the central Arctic coast of Canada (<a href="#fig20">fig. 20</a>). Its fall -migration appears to be southwest and south across the barren grounds -to Great Slave and Athabaska Lakes, where it joins thousands of other -waterfowl bound for their winter homes along the eastern coast of the -United States and the Gulf of Mexico. But when the Ross's geese -have traveled south approximately to the northern boundary of Montana, -they separate from their companions, and turning to the southwest -cross the Rocky Mountains and settle for the winter in California.</p> - -<p><span class="pagenum" id="Page_65">-65-</span></p> - -<div class="figcenter" id="fig21" style="width: 478px;"> - <img class="w100" src="images/fig21.png" width="478" height="522" alt="" /> - <div class="caption"><i>Figure 21.</i>—Breeding and wintering ranges of the western tanager. -See <a href="#fig22">figure 22</a> for the spring route taken by the birds breeding in the -northern part of the range.</div> -</div> - -<p>The route taken by the white-winged scoters that winter on the -Atlantic coast already has been indicated (p. 59). Some birds of this -species, however, winter on the Pacific coast from Puget Sound south -to southern California. Their passage by thousands up and down the -coast has been noted as far north as northwestern British Columbia. -The species is known to nest in Alaska, which may be the home of -some, at least, of the scoters that winter on the Pacific coast. If such -be the case, however, it must be admitted that a part of the route taken -<span class="pagenum" id="Page_66">-66-</span> -by the birds when on migration is unknown, though very few observations -are available from the interior of northern British Columbia, -across which the route may lie.</p> - -<p>The southward route of those migratory land birds of the Pacific -coast that in winter leave the United States extends chiefly through the -interior of California to the mouth of the Colorado River and on to -winter quarters in western Mexico.</p> - -<p>The movements of the western tanager show a migration route -that is in some ways remarkable. The species breeds in the mountains -from the northern part of Baja California and western Texas north -to northeastern British Columbia and southwestern Mackenzie. Its -winter range is in two discontinuous areas—southern Baja California -and eastern Mexico south to Guatemala (<a href="#fig21">fig. 21</a>). On the spring -migration the birds enter the United States about April 20, appearing -first in western Texas and the southern parts of New Mexico and -Arizona (<a href="#fig22">fig. 22</a>). By April 30 the vanguard has advanced evenly to -an approximate east-and-west line across central New Mexico, Arizona, -and southern California. But by May 10 the easternmost birds have -advanced only to southern Colorado, while those in the far west have -reached northern Washington. Ten days later the northward advance -of the species is shown as a great curve, extending northeastward -from Vancouver Island to central Albert and thence southeastward -to northern Colorado. Since these tanagers do not reach northern -Colorado until May 20, it is evident that those present in Alberta on -that date, instead of traveling northward through the Rocky Mountains, -which from the location of their summer and winter homes -would seem to be the natural route, reached there by the Pacific coast -route to southern British Columbia and thence across the mountains, -despite the fact that these are still partly covered with snow at that time.</p> - - -<h3 id="Pacific_oceanic_route">Pacific oceanic route</h3> - -<p>The route of the Pacific golden plover is fully as interesting and -as remarkable as the elliptical course followed by its eastern cousin -(<a href="#fig18">fig. 18</a>). The breeding range of the eastern golden plover extends -through Arctic America west to the northern coast of Alaska where, -in the vicinity of Point Barrow, it meets the nesting grounds of the -Pacific form, which is really an Asiatic subspecies. It breeds chiefly -in the Arctic coast region of Siberia and merely overflows onto the -Alaskan coast, some of the birds probably migrating south along the -<span class="pagenum" id="Page_67">-67-</span> -coast of Asia to winter quarters in Japan, China, India, Australia, New -Zealand, and Oceania, including the Hawaiian Islands, the Marquesas -Islands, and the Low Archipelago. Golden plovers in migration -have been observed at sea on a line that apparently extends from these -islands to the Aleutians, and it therefore appears certain that at least -some of the Alaskan birds make a nonstop flight across a landless sea -from Alaska to Hawaii. While it would seem incredible that any birds -could lay a course so straight as to attain these small oceanic islands, -2,000 miles south of the Aleutians, 2,000 miles west of Baja California, -and nearly 4,000 miles east of Japan, the evidence admits only the -conclusion that year after year this transoceanic round-trip journey -between Alaska and Hawaii is made by considerable numbers of -golden plovers.</p> - -<div class="figcenter" id="fig22" style="width: 471px;"> - <img class="w100" src="images/fig22.png" width="471" height="521" alt="" /> - <div class="caption"><i>Figure 22.</i>—Migration of the western tanager. The birds that arrive -in eastern Alberta by May 20 do not travel northward along the -eastern base of the Rocky Mountains, as in that region the van has -then only reached northern Colorado. Instead the isochronal lines -indicate that they migrate north through California, Oregon, and -Washington, and then cross the mountains of British Columbia.</div> -</div> - -<p><span class="pagenum" id="Page_68">-68-</span></p> - -<p>The Pacific oceanic route probably is used also by the arctic terns -that breed in Alaska, and possibly by those from the more western -tern colonies of Canada. This species is of regular occurrence on -the western coasts of both the United States and South America, -indicating that the western representatives travel southward to the -Antarctic winter quarters without the spectacular migration features -that appear to characterize the flight of those from the eastern part -of the continent (<a href="#fig8">fig. 8</a>).</p> - - -<h3 id="Arctic_routes">Arctic routes</h3> - -<p>In the discussion of the migration of the Arctic tern (p. 38) it was -noted that this species makes a very distinct west-to-east movement -across northern Canada, continuing the flight eastward across the -Atlantic Ocean toward the western coast of Europe. It seems likely -that there are other species, including the parasitic jaeger, that regularly -breed in the northern part of the Western Hemisphere but migrate -back to the Old World for their winter sojourn. Some others, as -the red-legged kittiwake and Ross's gull, remain near the Arctic region -throughout the year, retreating southward in winter only a few -hundred miles. The emperor goose in winter is found only a relatively -short distance south of its breeding grounds, and eider ducks, although -wintering in latitudes well south of their nesting areas, nevertheless -remain farther north than do the majority of other species of ducks.</p> - -<p>The routes followed by these birds are chiefly coastwise, and in the -final analysis may be considered as being tributary either to the Atlantic -or to the Pacific coast routes. The passage of gulls, ducks, the black -brant, and other water birds at Point Barrow, Alaska, and at other -points on the Arctic coast, has been noted by several observers, and -from present knowledge it may be said that the best defined Arctic -route in North America is the one that follows around the coast of -Alaska.</p> - -<p><span class="pagenum" id="Page_69">-69-</span></p> - -<div class="figcenter" id="fig23" style="width: 472px;"> - <img class="w100" src="images/fig23.png" width="472" height="585" alt="" /> - <div class="caption"><i>Figure 23.</i>—Distribution and migration of the red-eyed vireo. It is -evident that the red-eyed vireo has only recently invaded Washington -by an extension of its breeding range almost due west from the -upper Missouri Valley. Like the bobolink, however (<a href="#fig19">fig. 19</a>), the -western breeders do not take the short cut south or southeast from -their nesting grounds, but migrate spring and fall along the route -traveled in making this extension.</div> -</div> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_70">-70-</span></p> - -<h2 class="nobreak" id="Evolution_of_Migration_Routes"><i>Evolution of Migration Routes</i></h2> -</div> - - -<p>From the foregoing descriptions of migration routes it will be -observed that the general trend of migration in most species of North -American birds is northwest and southeast. It is comparatively easy -to trace the probable steps in the evolution of the migrations of some -species, and some routes have developed so recently that they still -plainly show their origin.</p> - -<p>The tendency is for eastern species to extend their ranges by pushing -westward, particularly in the north. For example, in the Stikine -River Valley of northern British Columbia and southwestern Alaska -the eastern nighthawk, eastern chipping sparrow, rusty blackbird, -eastern yellow warbler, redstart, and others have established breeding -stations at points 20 to 100 miles from the Pacific Ocean. The -robin, flicker, slate-colored junco, blackpolled and myrtle warblers, -and ovenbird, all common eastern species, also are established as breeding -birds in western Alaska, the ovenbird having been detected on the -lower Yukon River. These birds are essentially Atlantic and Mississippi -Flyway species, however, and so do not migrate in fall by any of -the Pacific or Central routes, but instead retrace their journey across -the mountains and move southward along the broad flyways of the East.</p> - -<p>The red-eyed vireo, a striking example of an abundant woodland -bird, is essentially an inhabitant of States east of the Great Plains, but -an arm of its breeding range extends northwest to the Pacific coast in -British Columbia (<a href="#fig23">fig. 23</a>). It seems evident that this is a range extension -that has taken place comparatively recently by a westward movement -from the upper Missouri Valley, and that the invaders retrace in -spring and fall the general route by which they originally entered the -country.</p> - -<p>In the case of the bobolink, a new extension of the breeding range, -and a consequent change in the migration of the species, has taken -place since the settlement of the country (<a href="#fig19">fig. 19</a>). A bird of damp -meadows, it was originally cut off from the Western States by the -intervening arid regions. But with the advent of irrigation and the -bringing of large areas under cultivation, small colonies of nesting -bobolinks have appeared at various western points, and now the species -is established as a regular breeder in the great mountain parks and -irrigated valleys of Colorado and elsewhere almost to the Pacific coast. -<span class="pagenum" id="Page_71">-71-</span> -In retracing their course to reach the western edge of the route followed -by the bulk of the bobolinks that breed in the northern United States -and southern Canada, these western pioneers must fly long distances -along a line that runs almost due east and west.</p> - -<p>Similarly it is possible to sketch what seems to be the logical evolution -of the remarkable routes of the golden plover (<a href="#fig18">fig. 18</a>). It may be -assumed that the eastern birds of this species first followed an all-land -route from the South American winter quarters through Central -America, Mexico, and Texas to the western parts of the Mississippi -Valley. As the migration route lengthened northward with the retreat -of the ice and the bird's powers of flight developed, there would -be a tendency to straighten the line and to shorten it by cutting off -some of the great curve through Mexico and Texas. First a short -flight across the western part of the Gulf of Mexico was probably -essayed. Proving successful, this was followed by flight lines that -moved farther east, until finally the roundabout curve through Texas -was entirely discarded and the flight made directly across the Gulf -to southern Louisiana.</p> - -<p>As the great areas in Canada were gradually added to the birds' -domain, other important factors arose, the chief being the attractiveness -of the vast stretches of coast and plain of the Labrador Peninsula, -which in fall offered a bountiful store of berries. The fall route therefore -worked eastward to the Gulf of St. Lawrence, thence southwest -along the coast to Florida and across the Gulf of Mexico to the Central -American mainland. A series of shortening flights followed to take -out the great curve of the Atlantic coast. A relatively short ocean -flight was probably attempted, say from Cape Cod to the Bahama -Islands, Cuba, and Jamaica, followed eventually by the long direct -oceanic route as it is now known.</p> - -<p>As the Labrador Peninsula in spring is bound by frost and shrouded -in fog while the season advances rapidly through the interior, the -oceanic route proved useful only in fall, and the spring flight continued -through the Mississippi Valley. This outline, although entirely hypothetical, -gives a probable and fairly plausible explanation of the origin -of this wonderful route, particularly when it is remembered that migration -routes as now known are evolutions—age-long modifications -of other routes.</p> - -<p>The evolution of the migration route of the Pacific golden plover -may be explained in a similar fashion. At first the route probably -<span class="pagenum" id="Page_72">-72-</span> -followed the Asiatic coast, through the Malay Peninsula and Oceania, -thence east in a great curve to the Low Archipelago, with individuals -and flocks dropping out to winter at many points along the way. The -Siberian birds probably continue to follow this ancient highway, but -those nesting in Alaska began a long evolutionary series of flights that -cut down the length of their journey by shortening the curve, until -finally the transoceanic route of the present day was developed.</p> - -<p>This theory of the evolution of migration routes has been questioned -by some ornithologists on the ground that it implies the possession in -some degree of reasoning powers such as would be used by human -beings. This opposition suggests that changes in migration routes -might develop suddenly following mass survival of birds that were -driven over the new route by a storm on some specific occasion. In -the language of genetics, the new route would be, in effect, a mutation, -rather than the result of an accumulation of infinitesimal variations. -There is some evidence in support of this opposing theory. For example, -information from the Hudson's Bay Co. post at Great Whale -River, on the southeastern coast of Hudson Bay, indicates that in 1884 -the snow geese suddenly changed their route from the eastern to the -western coasts of Hudson and James Bays. According to one report, -this change was caused by strong winds from the south which caught -the birds in their fall migration and caused them to cross the entrance -of James Bay from Cape Jones to the western side; the route thus reportedly -forced upon them was then used in succeeding years.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Vertical_Migration"><i>Vertical Migration</i></h2> -</div> - - -<p>In the effort to find winter quarters furnishing satisfactory living -conditions, many North American birds fly hundreds of miles across -land and sea. Others, however, are able to attain their objective merely -by moving down the sides of a mountain. In such cases a few hundred -feet of altitude correspond to hundreds of miles of latitude. Movements -of this kind, known as "vertical migrations," are found wherever -there are large mountain ranges. In the Rocky Mountain region they -are particularly notable, as chickadees, rosy finches, juncos, pine grosbeaks, -and some other species that nest in the Alpine Zone move down -to the lower levels to spend the winter. It has been noted that such -species as Williamson's sapsucker and the western wood pewee, which -<span class="pagenum" id="Page_73">-73-</span> -nest in the higher mountains, move down to the lower regions in -August following the breeding season. There is a distinct tendency -among the young of mountain-breeding birds to work down to the -lower levels as soon as the nesting season is over. The sudden increases -among birds in the edges of the foothills are particularly noticeable -when cold spells with snow or frost occur at the higher altitudes.</p> - -<p>Some species that normally breed in the Hudsonian or Arctic Zones -find suitable breeding areas on the higher levels of the mountains, as for -example the pipit, or titlark, which breeds on the tundra of Alaska and -northern Canada and also south as far as Colorado on the summits of -many peaks in the Rocky Mountains. On the other hand, a few -species, as the Clark's crow, or nutcracker, nest at relatively low altitudes -in the mountains and as the summer advances move higher up, -thus performing a vertical migration that in a sense is comparable with -the post-breeding movements of herons on the Atlantic coast. These -illustrations show that the length of a migration route may depend -upon factors other than latitude.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Vagrant_Migration"><i>Vagrant Migration</i></h2> -</div> - - -<p>The most striking feature of the migrations of some of the herons -is a northward movement after the nesting season. The young of -some species commonly wander late in the summer and in fall, sometimes -traveling several hundred miles north of the district in which -they were hatched. The little blue heron breeds commonly north -to South Carolina, and by the last of July the young birds begin to -appear along the Potomac, Patuxent, and Susquehanna Rivers, tributary -to Chesapeake Bay. Although almost all are immature individuals, -as shown by their white plumage, an occasional adult may be -noted. With them come egrets and snowy herons and on occasion -all three species will travel in the East as far north as New England, -and in the Mississippi Valley to southeastern Kansas and Illinois. In -September most of them disappear, probably returning south by the -same route.</p> - -<p>The black-crowned night heron has similar wandering habits, and -young birds banded in a large colony at Barnstable, Mass., have been -recaptured the same season north to Maine and Quebec and west to -New York. This habit seems to be shared by some of the gulls also, -although here the evidence is not so conclusive. Herring gulls banded -<span class="pagenum" id="Page_74">-74-</span> -as chicks at colonies in the Great Lakes have scattered in all directions -after the breeding season, some having been recovered well north in -Canada.</p> - -<p>These movements may be considered as migration governed only by -the availability of food, and they are counteracted in fall by a directive -migratory impulse that carries back to their normal winter homes in -the south those birds that after the nesting period attained more -northern latitudes. They are not to be compared with the great invasions -of certain birds from the North. Classic examples of the latter -in the eastern part of the country are the periodic flights of crossbills. -Sometimes these migrations will extend well south into the Carolinian -Zone.</p> - -<p>Snowy owls are noted for occasional invasions that have been correlated -with the periodic maximum of Arctic foxes and the lemming -cycle in the north. According to Gross (1947) 24 major invasions -occurred between 1833 and 1945. The interval between these varied -from 2 to 14 years, but nearly half (11) were at intervals of 4 years. -A great flight occurred in the winter of 1926-27 when more than 1,000 -records were received from New England alone, but the largest on -record was in 1945-46 when the "Snowy Owl Committee" of the American -Ornithologists' Union received reports of 13,502 birds, of which -4,443 were reported as killed. It extended over the entire width of the -continent from Washington and British Columbia to the Atlantic coast -and south to Nebraska, Illinois, Indiana, Pennsylvania, and Maryland. -One was taken as far south as South Carolina.</p> - -<p>In the Rocky Mountain region great flights of the beautiful Bohemian -waxwing are occasionally recorded. The greatest invasion in the history -of Colorado ornithology occurred in February 1917, at which time -the writer estimated that at least 10,000 were within the corporate -limits of the city of Denver. The last previous occurrence of the species -in large numbers in that section was in 1908.</p> - -<p>Evening grosbeaks likewise are given to performing more or less -wandering journeys, and curiously enough, in addition to occasional -trips south of their regular range, they travel east and west, sometimes -covering long distances. For example, grosbeaks banded at Sault -Ste. Marie, Mich., have been recaptured on Cape Cod, Mass., and in the -following season have been retrapped at the banding station. Banding -records demonstrate that this east-and-west trip across the northeastern -part of the country is sometimes made also by purple finches.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_75">-75-</span></p> - -<h2 class="nobreak" id="Perils_of_Migration"><i>Perils of Migration</i></h2> -</div> - - -<p>The period of migration is a season full of peril for birds. Untold -thousands of the smaller migrants are destroyed each year by storms -and through attacks of predatory birds, mammals, and reptiles. If -each pair of adult birds should succeed in raising two fledglings to -maturity, the population of migratory birds would have a potential -annual increase of 100 percent and the world would soon be heavily -overpopulated with them. Since there is no such increase it is evident -that the annual mortality from natural causes is heavy enough to keep -it in check.</p> - - -<h3 id="Storms">Storms</h3> - -<p>Of the various factors limiting the abundance of birds, particularly -the smaller species, storms are the most potent. Special sufferers are -those birds that in crossing broad stretches of water are forced down -by a storm within reach of the waves. Such a catastrophe was once -seen from the deck of a vessel in the Gulf of Mexico, 30 miles off the -mouth of the Mississippi River. Great numbers of migrating birds, -chiefly warblers, had accomplished nearly 95 percent of their long -flight and were nearing land, when, caught by a norther against which -they were unable to contend, hundreds were forced into the waters of -the Gulf and drowned. On another occasion, on Lake Michigan, a -severe storm came up at a time when large numbers of migratory -birds were crossing and forced numerous victims into the waves. During -the fall migration of 1906, when thousands of birds were crossing -Lake Huron, a sudden drop in temperature accompanied by a heavy -snowfall resulted in the death of incredible numbers. Literally thousands -were forced into the water and subsequently cast up along the -beaches, where in places their bodies were piled in windrows. On one -section of the beach the dead birds were estimated at 1,000 per mile, -and at another point at 5 times that number. Most of them were species -that rank among our most desirable birds as destroyers of insects and -weed seeds, including slate-colored juncos, tree sparrows, white-throated -sparrows, swamp sparrows, winter wrens, and golden-crowned -kinglets, together with many brown creepers, hermit thrushes, -warblers, vireos, and others.</p> - -<p>Of all species of North American birds, the Lapland longspur seems -to be the most frequent victim of mass destruction from storms. These -<span class="pagenum" id="Page_76">-76-</span> -birds sometimes congregate in enormous numbers where grass or weed -seed is abundant. Almost every winter brings in reports of their -death by thousands somewhere in the Middle West. While migrating -northward at night they have encountered blinding storms of wet, -clinging snow, which have so bewildered them that they have flown -into various obstructions, or have sunk to the ground and perished of -exposure and exhaustion. In 1907 an experienced ornithologist estimated -that 750,000 longspurs were lying dead on the ice of 2 lakes in -Minnesota, each about 1 square mile in extent, and dead birds were -reported in greater or less abundance on this occasion over an area -of more than 1,500 square miles. The heaviest mortality occurred in -towns, where, bewildered by the darkness and the heavy falling snow, -some of the birds congregating in great numbers flew against various -obstacles and were killed or stunned, while many others fell to the -ground exhausted. Similar catastrophes have been reported from -eastern Colorado, Nebraska, and North Dakota.</p> - -<p>During the early part of June 1927, a hailstorm of exceptional severity -in and around Denver, Colo., killed large numbers of robins, -meadow larks, sparrows, and others. The lawns of parks were strewn -with the bodies of these birds, and many lay dead in their nests where -they were covering their eggs or young when the storm broke.</p> - - -<h3 id="Aerial_obstructions">Aerial obstructions</h3> - -<p>Lighthouses, lightships, tall bridges, piers, monuments, and other -aerial obstructions have been responsible for a tremendous destruction -of migratory birds. Beams of the lanterns at light stations have a -powerful attraction for nocturnal travelers of the air that may be -likened to the fascination for lights that also is shown by many insects, -particularly night-flying moths. The attraction is not so potent in -clear weather, but when the atmosphere is moisture laden, as in a heavy -fog, the rays have a dazzling effect that lures the birds to their death. -They may fly straight up the beam and dash themselves headlong -against the glass, or they may keep fluttering around the source of the -light until exhausted, and then drop to the rocks or waves below. The -fixed, white, stationary light located 180 feet above sea level at Ponce -de Leon Inlet (formerly Mosquito Inlet), Fla., has caused great destruction -of bird life even though the lens is shielded by wire netting. -On one occasion an observer gathered up a bushel-basketful of warblers, -sparrows, and other small passerine birds that had struck during the -<span class="pagenum" id="Page_77">-77-</span> -night. The birds apparently beat themselves to death against the -wire or fell exhausted to the concrete pavement below, frequently -to be destroyed there by cats or skunks. Two other lighthouses at -the southern end of Florida, Sombrero Key and Fowey Rocks, have -been the cause of a great number of bird tragedies, while heavy mortality -has been noted also at some of the lights on the Great Lakes and -on the coast of Quebec. It is the fixed white lights that cause such -disasters to birds, as the stations equipped with flashing or red lights do -not present such strong attractions. That it is not a mere case of geographical -location has been demonstrated, for it is observed that when -fixed white lights have been changed to red or flashing lights, the -migrating birds are no longer endangered. At some of the light stations -in England and elsewhere, shelves and perches have been placed -below the lanterns to afford places where birds can rest until they have -overcome their bewilderment.</p> - -<p>For many years at the National Capital, the Washington Monument, -although unilluminated, caused the destruction of large numbers of -small birds, due apparently to their inability to see this obstacle in their -path, towering more than 555 feet into the air. One morning in the -spring of 1902 the bodies of nearly 150 warblers, sparrows, and other -birds were found about its base. Then, as the illumination of the city -was improved and the Monument became more visible at night, the -loss became steadily less, until by 1920 only a few birds would be killed -during an entire migration. On November 11, 1931, however, as part -of the Armistice Day celebration, batteries of brilliant floodlights -grouped on all four sides about the base of the Monument were added -to the two searchlights already trained on the apex, so that the lighted -shaft probably corresponds in brilliancy to a very low magnitude -lighthouse lantern. Airplane pilots have ventured opinions that on -a clear night it could be seen for 40 miles. It is certain that there is -an extensive area of illumination, and on dark nights, when there are -gusty, northerly winds and the nocturnal travelers seem to fly at lower -altitudes, many of them are attracted to the Monument as to a lighthouse -beacon. As they approach from the north a last-minute attempt -to avoid it causes them to veer off to the east or the west where they are -literally sucked in and dashed against the southern face of the shaft. -During the fall migration of 1932 more than 500 warblers, vireos, -thrushes, kinglets, sparrows, and others were killed. Since that year -the mortality has been less, but the Monument at times remains a -<span class="pagenum" id="Page_78">-78-</span> -serious menace to birds during migration and some are killed nearly -every fall.</p> - -<p>When the torch on the Statue of Liberty in New York Harbor was -kept lighted, it caused an enormous destruction of bird life, tabulations -showing as many as 700 birds killed in a single month.</p> - -<p>In September 1948, bird students were startled by news of the wholesale -destruction of Maryland yellowthroats, redstarts, ovenbirds, and -others that were dashed against the 1,250-foot high Empire State Building -in New York City, the 491-foot high Philadelphia Saving Fund -Society Building in Philadelphia, and the 450-foot high WBAL radio -tower in Baltimore. In New York the birds continued to crash into -the Empire State Building over a 6-hour period and their bodies were -scattered over a four-block area. The mortality was so heavy in Philadelphia -that it was impossible to use the sidewalk below the sky-scraper -until the birds had been gathered. A study of the weather -conditions prevailing at this time in the Atlantic coastal region suggests -the probable cause of this catastrophe. By early morning on -September 11 a mass of cold, southward-flowing air had just reached -New York City where it was forcing upward and was being overridden -by a mass of warm, northward-flowing air. Presumably the -migrants were riding the upper levels of the southbound current which, -in the contact zone with the northbound current, was being deflected -earthward, thus causing the birds to fly lower and lower until they -were below the tower of the Empire State Building. Clouds and gusty -winds in the zone of contact between the two air masses reduced visibility -and disrupted avian navigation with the result that the confused -travelers crashed into the stone and steel obstruction. As the cold air -mass continued to move southward, the situation was repeated at -Philadelphia and at Baltimore.</p> - - -<h3 id="Exhaustion">Exhaustion</h3> - -<p>Although it would seem that the exertion incident to the long flights -of many species of migratory birds would result in their arrival at their -destination in a state bordering on exhaustion, this is contrary to the -truth. Both the soaring and the sailing of birds show them to be -proficient in the use of factors employed in aerial transportation that -only recently have become understood and imitated by aeronautical -engineers. The use of ascending currents of air, employed by all soaring -birds, and easily demonstrated by observing the gulls that glide -<span class="pagenum" id="Page_79">-79-</span> -hour after hour along the windward side of a ship, are now utilized -by man in his operation of gliders. Moreover, the whole structure of -a bird renders it the most perfect machine for extensive flight that the -world has ever known. Hollow, air-filled bones, making an ideal -combination of strength and lightness, and the lightest and toughest -material possible for flight in the form of feathers, combine to produce -a perfect flying machine. Mere consideration of a bird's economy of -fuel or energy also is enlightening. The golden plover, traveling -over the oceanic route, makes the entire distance of 2,400 miles from -Nova Scotia to South America without stop, probably requiring about -48 hours of continuous flight. This is accomplished with the consumption -of less than 2 ounces of fuel in the form of body fat. To be as -economical in operation, a 1,000-pound airplane would consume in a -20-mile flight not the gallon of fuel usually required, but only a single -pint.</p> - -<p>The sora, or Carolina rail, which is such a notoriously weak flyer that -at least one writer was led to infer that most of its migration was made -on foot, has one of the longest migration routes of any member of the -family, and easily crosses the wide reaches of the Caribbean Sea. The -tiny ruby-throated hummingbird crosses the Gulf of Mexico in a single -flight of more than 500 miles.</p> - -<p>While birds that have recently arrived from a protracted flight over -land or sea sometimes show evidences of being tired—as, for example, -pintail ducks that have flown from the North American mainland to -the Hawaiian Islands—their condition is far from being a state of exhaustion. -With a few hours' rest and a crop well filled with proper -food, most birds exhibit eagerness to resume their journey. The popular -notion that birds find the long ocean flights excessively wearisome -and that they sink exhausted when terra firma is reached, generally -does not agree with the facts. The truth lies in the opposite direction, -as even small land birds are so little averse to ocean voyages that they -not only cross the Gulf of Mexico at its widest point, but may even pass -without pause over the low, swampy coastal plain to the higher regions -beyond. Under favorable conditions birds can fly when, where, and -how they please. Consequently the distance covered in a single flight -is governed chiefly by the food supply. Exhaustion, except as the result -of unusual factors, cannot be said to be an important peril of -migration.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_80">-80-</span></p> - -<h2 class="nobreak" id="Influence_of_the_Weather_on_Migration"><i>Influence of the Weather on Migration</i></h2> -</div> - - -<p>The state of the weather at any point has little if anything to do with -the time of arrival of migratory birds. This is contrary to the belief -of observers who have thought that they could foretell the appearance -of various species by a study of the weather conditions. Though the -insistent crescendo note of the ovenbird is ordinarily associated with -the full verdure of May woods, this bird has been known to reach its -breeding grounds in a snowstorm and the records of its arrival in -southern Minnesota show a temperature variation from near freezing -to full summer warmth. Temperatures at arrival of several other -common birds vary from 14 degrees between highest and lowest temperatures -to 37 degrees, the average variation being about 24 degrees.</p> - -<p>It should be remembered that North American species spending the -winter months in tropical latitudes experience no marked changes in -climatic conditions from November to March or April, yet frequently -they will start the northward movement in January or February. -This is in obedience to physiological promptings and has no relation -to the prevailing weather conditions. For migratory birds the winter -season is a period of rest, a time when they have no cares other than -those associated with the daily search for food or escape from their -natural enemies. Their migrations, however, are a vital part of their -life cycles, which have become so well adjusted that the seasons of -travel correspond in general with the major seasonal changes on their -breeding grounds. With the approach of spring, therefore, the reproductive -impulse awakens, and each individual bird is irresistibly impelled -to start the journey that ends in its summer home.</p> - -<p>In other words, the evidence indicates that the urge to migrate is -so ingrained that each species moves north in spring when the average -weather that will be encountered is not unendurable. The word -"average" must be emphasized since it appears obvious that the migrations -of birds have so evolved that in general they synchronize with -average climatic conditions. The hardy species travel early, fearless -of the blasts of retreating winter, while the more delicate kinds come -later when there is less danger of encountering prolonged periods of -inclement weather. Some of the hardy birds pause in favorable areas -and allow the spring season to advance. Then, by rapid travel they -again overtake it, or, as sometimes happens, they actually outstrip it. -<span class="pagenum" id="Page_81">-81-</span> -Occasionally this results in some hardship, and rarely in the destruction -of large numbers of individuals. Cases are known where early -migrating bluebirds have been overwhelmed by late winter storms. -Nevertheless, unless such climatic conditions are prolonged, no serious -effect on the species is noted. The soundness of the bird's instincts is -evidenced by the fact that natural catastrophes, great though they may -be, do not permanently diminish the avian populations.</p> - -<p>As has been pointed out, the advance of average temperature lines, -known as isotherms, is found to correspond closely with the northward -movements of certain species. For example, the northward travels of -the Canada goose are found to coincide with the advance of the isotherm -of 35° F. (<a href="#fig4">fig. 4</a>).</p> - -<p>The spring flight of migrants, if interrupted for any reason, is -resumed when weather conditions again become favorable, and it is -probable that all instances of arrival of birds in stormy weather can -be explained on the theory that the flight was begun while the weather -was auspicious. The state of the weather when a flight starts at any -southern point, the relation of that place to the average position of the -bird under normal weather conditions on that date, and the average -rate of migratory flight, are data basic to any reasonably accurate prediction -of the time arrival may be expected in northern areas.</p> - -<p>Head winds are as unfavorable to migration as is rain or snow, -as they greatly increase the labor of flight and cut down the speed of -cross-country travel. If such winds have a particularly high velocity -they may force down the weaker travelers, and when this happens over -water areas, large numbers of birds are lost. Even strong winds that -blow in the direction of aerial travel are unfavorable for the birds, as -they interfere with their balance and disarrange their feathers. Moderate -tail winds and cross or quartering breezes appear to offer the best -conditions for the passage of the migrants.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Problems_of_Migration"><i>Problems of Migration</i></h2> -</div> - - -<h3 id="Banding_studies">Banding studies</h3> - -<p>The study of living birds by the banding method, whereby great -numbers of individuals are marked with numbered aluminum leg -rings, has come to be recognized as a most accurate means of ornithological -research. Since 1920, banding work in North America has -been under the direction of the Fish and Wildlife Service in cooperation -<span class="pagenum" id="Page_82">-82-</span> -with the Dominion Wildlife Service of Canada. Every year -voluntary cooperators, working under permit, place bands on thousands -of birds, game and nongame, large and small, migratory and nonmigratory, -each band carrying a serial number and the legend, NOTIFY -FISH AND WILDLIFE SERVICE, WASHINGTON, D. C., or on -the smaller sizes an abbreviation thereof. When a banded bird is -reported from a second locality, a definite fact relative to its movements -becomes known, and a study of many cases of this nature develops -more and more complete knowledge of the details of migration.</p> - -<p>The records of banded birds are also yielding other pertinent information -relative to their migrations, such as the exact dates of arrival -and departure of individuals, the length of time that different birds -pause on their migratory journeys to feed and rest, the relation between -weather conditions and the starting times for migration, the -rates of travel of individual birds, the degree of regularity with which -birds return to the exact summer or winter quarters used in former -years, and many other details that could be learned in no other manner. -Banding stations that are operated systematically throughout the year, -therefore, are supplying much information concerning the movements -of migratory birds that heretofore could only be surmised. (See Appendix II, -p. 92 for instructions on reporting the recovery of banded -birds.)</p> - - -<h3 id="Movements_of_residents">Movements of residents</h3> - -<p>Typical migration consists of definite movements that are repeated -regularly year after year, and it is to these that the term is generally -restricted. It is desirable, however, if only for purposes of comparison, -that some account be taken of the movements of some other birds, -which, while not typical, do possess some of the characteristics of true -migration. Data on this subject are being collected through bird -banding.</p> - -<p>There are several species that are customarily grouped under the -heading "permanent residents," the term implying that these birds -do not travel but remain throughout the year in one locality. Among -these are the cardinal, the tufted titmouse, the wrentit, the Carolina -wren, the house finch, the bobwhite, the California quail, and the -ruffed grouse. Each species may be present constantly throughout the -year, although in the northern part of the range there is probably a -slight withdrawal of the breeding birds in winter. The individuals to -<span class="pagenum" id="Page_83">-83-</span> -be seen at that season, therefore, may not always be the same as those -observed during the summer. It is certain, however, that these species -do not regularly perform extensive journeys.</p> - -<p>While the blue jay is disposed to be secretive, it is such a showy and -noisy bird that it is not likely to escape notice. In the vicinity of -Washington, D. C., as in many other places, it is present the year -round, but at the end of September or early in October when the -weather is becoming cooler, troops of jays are sometimes seen working -southward through the trees. A corresponding northward movement -occurs again in May. This is unquestionably a migration to and from -some winter range, but its extent or significance is not now known. -Some light is being shed on the matter, however, through the records -of banded birds, and these eventually will fill in a more perfect picture -of the movements of this species. One jay, banded on September 14, -1923, at Waukegan, Ill., was killed at Peruque, Mo., on November 15 -of the same year; another, banded at Winnetka, Ill., on June 16, 1925, -was retaken at Sulphur Rock, Ark., the following December 10; a -third, banded on May 6, 1925, at Whitten, Iowa, was recaptured at -Decatur, Ark., on January 22, 1926. These three birds unquestionably -had made a flight that had every appearance of being a true migration -to winter quarters in Missouri and Arkansas.</p> - -<p>The black-capped chickadee is apparently resident in many places, -but occasionally in winter it invades the range of the southern Carolina -chickadee, and in northern Canada it is regularly a migrant.</p> - -<p>In the coastal plain between Washington, D. C., and the Atlantic -Ocean, the white-breasted nuthatch is usually absent during the summer, -nesting at that season in the higher, or piedmont, country. Late -in fall, however, it appears in fair abundance in the wooded bottoms, -remaining at the lower levels until the following March or April.</p> - -<p>Some birds, including the screech owl, bobwhite, Carolina wren, -and mockingbird, seem to be actually sedentary, but even these are -sometimes given to post-breeding wanderings. Ordinarily bobwhites -that are marked with numbered bands are seldom retaken far from the -area where banded, but sometimes they will travel 10 miles or more. -A screech owl banded at Glenwood, Minn., in March, was recovered -the following December at Emmetsburg, Iowa, 180 miles south. Such -flights, however, are probably more in the nature of a search for new -feeding areas, or to escape from a winged enemy, than a true migratory -journey.</p> - -<p><span class="pagenum" id="Page_84">-84-</span></p> - - -<h3 id="Migration_white-throated_sparrow">Migration of the white-throated sparrow</h3> - -<p>The white-throated sparrow, one of the most abundant members -of its family, breeds from northern Mackenzie and the southern part of -the Ungava Peninsula south to southern Montana, northern Pennsylvania, -and Massachusetts. The winter range extends from the southern -part of the breeding range south to the Gulf coast and northeastern -Mexico. It is therefore a common migrant in many sections. Since -it is a ground-feeding bird and is readily attracted to the vicinity of -dwellings, it has been banded in large numbers, the total to November -14, 1949, being nearly 283,500. It would be expected that these would -yield a comparable number of return records that would furnish -basic data relative to the migrations of the species. Such, however, is -not the case. Banded white-throated sparrows are rarely recaptured -at stations between the breeding and wintering grounds. Operators of -stations in the winter area, as Thomasville, Ga., and Summerville, S. C., -have obtained return records showing that these birds do come back -to the exact winter quarters occupied in previous seasons. The fact -that they do not again visit banding stations on their migration routes -indicates some unusual aspects of their travels, which it is hoped will -eventually be discovered by banding studies. Problems of this type -constitute definite challenges to the student of bird migration.</p> - - -<h3 id="Migration_yellow-billed_loon">Migration of the yellow-billed loon</h3> - -<p>The semiannual movements of the yellow-billed loon present an -unusual problem in migration. It breeds along the Arctic coast, probably -from Cape Prince of Wales eastward to Franklin Bay, and also -in the interior of northern Canada south to Clinton-Colden, Aylmer, -and Artillery Lakes, where it is rather common. It has been reported -as already present by May 25 at the mouth of the Liard River, in southwestern -Mackenzie. This coincides with the time that first arrivals -are noted fully 700 miles north, at Point Barrow, Alaska. The problem -has been to ascertain the route used by these birds to their principal -nesting grounds in the interior.</p> - -<p>For a long time it was believed that this big diver did not winter -in large numbers anywhere on the Pacific coast, and it had been supposed -that the spring route extended 2,000 miles northeastward from a -wintering ground somewhere in eastern Asia to Bering Strait, then -500 miles still northeast to round Point Barrow, then 500 miles east to -<span class="pagenum" id="Page_85">-85-</span> -the coast of Mackenzie, and finally 700 miles south—in spring—to the -region near the eastern end of Great Slave Lake.</p> - -<p>The yellow-billed loon is a powerful flier, and it is probable that -this suggested route is correct for those birds that breed in the northern -coastal regions. A reasonable doubt may be entertained, however, -whether the breeding birds of Great Slave Lake and contiguous areas -reach their breeding grounds by the 700-mile flight south from the -Arctic coast. Within recent years it has been found that these birds -are fairly common in the maze of channels and islands off the coast of -southeastern Alaska as late as the last of October and in February. -Possibly they are present there during the period from November -through January also, or they may at that time move farther off shore -and so escape detection. If this region is an important wintering -ground, as seems probable, then it is likely that the breeding birds of -the interior reach their nesting grounds by a flight eastward across -the mountains, a trip that is well within their flying ability, rather than -by a circuitous route around the northern coast. The air-line distance -from southeastern Alaska to the mouth of the Liard River is in fact -less than the distance to that point from the mouth of the Mackenzie.</p> - -<p>Differing routes to various parts of a large breeding or wintering -ground, and used by large groups of individuals of other species, are -not unknown. For example, the redhead duck is one of the common -breeding ducks of the Bear River marshes of Utah, where a great many -have been banded each summer. The recovery records of banded redheads -show that while many travel westward to California, others -start their fall migration in the opposite direction and, flying eastward -across the Rocky Mountains, either turn southeast across the plains -to the Gulf of Mexico, or deliberately proceed in a northeasterly direction -to join the flocks of this species moving toward the Atlantic coast -from the prairie regions of southern Canada.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Conclusions"><i>Conclusions</i></h2> -</div> - - -<p>The migration of birds as it is known today had its beginning in -times so remote that its origins have been entirely obscured, and it -can be interpreted now only in terms of present conditions. The -causes underlying migration are exceedingly complex. The mystery -that formerly cloaked the periodic travels of birds, however, has been -largely dispelled through the fairly complete information that is now -<span class="pagenum" id="Page_86">-86-</span> -available concerning the extent and times of the seasonal journeys of -most of the species. Many gaps, however, still remain in our knowledge -of the subject. Much has been learned, and present knowledge -is being placed on record, but it must be left to future study to clear -away many of the uncertainties that continue to make bird migration -one of the most fascinating subjects in the science of ornithology.</p> - -<p>Each kind of bird seems to have its own reaction to its environment, -so that the character of movement differs widely in the various species, -and seldom do any two present the same picture. In fact, bird migration -has been described as a phase of geographic distribution wherein -there is a more or less regular seasonal shifting of the avian population -caused by the same factors that determine the ranges of the sedentary -species. If this view is correct, then it must be recognized that the far-reaching -works of man in altering the natural condition of the earth's -surface can so change the environment necessary for the well-being of -the birds as to bring about changes in their yearly travels. The nature -and extent of the changes wrought by man on the North American -Continent are easily apparent. Forests have been extensively cut away -and their places have been taken by second growth or cultivated land, -and wide stretches of prairie and plain have been broken up, irrigated, -and devoted to agriculture. These great changes are exerting a profound -effect upon the native bird populations, and the various species -may be either benefited or adversely affected thereby.</p> - -<p>The Federal Government has recognized its responsibility to the -migratory birds under changing conditions brought about by man, -and by enabling acts for carrying out treaty obligations, it is now giving -most species legal protection under regulations administered by the -Fish and Wildlife Service. Much is being done by legislation for the -welfare of the birds. The effectiveness of these conservation laws, -however, is increased in the same measure that the people of the country -become acquainted with the facts in the life histories of the migrants -and interest themselves personally in the well-being of the various -species. Long before the white man came to America the birds had -established their seasonal lanes of migration throughout the Western -Hemisphere. The economic, inspirational, and esthetic values of these -migratory species dictate that they be permitted to continue their long-accustomed -and still-mysterious habits of migration from clime to -clime.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_87">-87-</span></p> - -<h2 class="nobreak" id="Appendix_I">Appendix I—<i>List of Birds Mentioned in the Text</i></h2> -</div> - - -<table summary="Bird List"> -<tr> - <td class="tdl bt bb">Common name</td> - <td class="tdl bt bb">Scientific name</td> -</tr> -<tr> - <td class="tdl">American egret</td> - <td class="tdl"><i>Casmerodius albus egretta</i></td> -</tr> -<tr> - <td class="tdl">Arctic tern</td> - <td class="tdl"><i>Sterna paradisaea</i></td> -</tr> -<tr> - <td class="tdl">Atlantic brant</td> - <td class="tdl"><i>Branta bernicla hrota</i></td> -</tr> -<tr> - <td class="tdl">Atlantic golden plover</td> - <td class="tdl"><i>Pluvialis dominica dominica</i></td> -</tr> -<tr> - <td class="tdl">Bank swallow</td> - <td class="tdl"><i>Riparia riparia</i></td> -</tr> -<tr> - <td class="tdl">Barn swallow</td> - <td class="tdl"><i>Hirundo rustica erythrogaster</i></td> -</tr> -<tr> - <td class="tdl">Bartramian sandpiper or upland plover </td> - <td class="tdl"><i>Bartramia longicauda</i></td> -</tr> -<tr> - <td class="tdl">Belted kingfisher</td> - <td class="tdl"><i>Ceryle alcyon</i></td> -</tr> -<tr> - <td class="tdl">Black-and-white warbler</td> - <td class="tdl"><i>Mniotilta varia</i></td> -</tr> -<tr> - <td class="tdl">Black-billed cuckoo</td> - <td class="tdl"><i>Coccyzus erythropthalmus</i></td> -</tr> -<tr> - <td class="tdl">Black brant</td> - <td class="tdl"><i>Branta bernicla nigricans</i></td> -</tr> -<tr> - <td class="tdl">Black-capped chickadee</td> - <td class="tdl"><i>Parus atricapillus atricapillus</i></td> -</tr> -<tr> - <td class="tdl">Black-crowned night heron</td> - <td class="tdl"><i>Nycticorax nycticorax hoactli</i></td> -</tr> -<tr> - <td class="tdl">Black duck</td> - <td class="tdl"><i>Anas rubripes</i></td> -</tr> -<tr> - <td class="tdl">Black-headed grosbeak</td> - <td class="tdl"><i>Pheucticus melanocephalus</i></td> -</tr> -<tr> - <td class="tdl">Blackpolled warbler</td> - <td class="tdl"><i>Dendroica striata</i></td> -</tr> -<tr> - <td class="tdl">Black-throated blue warbler</td> - <td class="tdl"><i>Dendroica caerulescens</i></td> -</tr> -<tr> - <td class="tdl">Bluebird</td> - <td class="tdl"><i>Sialia sialis</i></td> -</tr> -<tr> - <td class="tdl">Blue goose</td> - <td class="tdl"><i>Chen caerulescens</i></td> -</tr> -<tr> - <td class="tdl">Blue jay</td> - <td class="tdl"><i>Cyanocitta cristata</i></td> -</tr> -<tr> - <td class="tdl">Bluethroat</td> - <td class="tdl"><i>Cyanosylvia suecica</i></td> -</tr> -<tr> - <td class="tdl">Blue-winged teal</td> - <td class="tdl"><i>Anas discors</i></td> -</tr> -<tr> - <td class="tdl">Bobolink</td> - <td class="tdl"><i>Dolichonyx orizivorus</i></td> -</tr> -<tr> - <td class="tdl">Bobwhite</td> - <td class="tdl"><i>Colinus virginianus</i></td> -</tr> -<tr> - <td class="tdl">Bohemian [greater] waxwing</td> - <td class="tdl"><i>Bombycilla garrulus pallidiceps</i></td> -</tr> -<tr> - <td class="tdl">Brewer's blackbird</td> - <td class="tdl"><i>Euphagus cyanocephalus</i></td> -</tr> -<tr> - <td class="tdl">Broad-winged hawk</td> - <td class="tdl"><i>Bueto platypterus</i></td> -</tr> -<tr> - <td class="tdl">Bronzed grackle</td> - <td class="tdl"><i>Quiscalus guiscula versicolor</i></td> -</tr> -<tr> - <td class="tdl">Brown [tree] creeper</td> - <td class="tdl"><i>Certhia familiaris</i></td> -</tr> -<tr> - <td class="tdl">Cackling [Canada] goose</td> - <td class="tdl"><i>Branta canadensis minima</i></td> -</tr> -<tr> - <td class="tdl">California quail</td> - <td class="tdl"><i>Lophortyx californica</i></td> -</tr> -<tr> - <td class="tdl">Canada goose</td> - <td class="tdl"><i>Branta canadensis</i></td> -</tr> -<tr> - <td class="tdl">Canvasback</td> - <td class="tdl"><i>Aythya valisineria</i></td> -</tr> -<tr> - <td class="tdl">Cape May warbler<span class="pagenum" id="Page_88">-88-</span></td> - <td class="tdl"><i>Dendroica tigrina</i></td> -</tr> -<tr> - <td class="tdl">Cardinal</td> - <td class="tdl"><i>Richmondena cardinalis</i></td> -</tr> -<tr> - <td class="tdl">Carolina chickadee</td> - <td class="tdl"><i>Parus carolinensis</i></td> -</tr> -<tr> - <td class="tdl">Carolina wren</td> - <td class="tdl"><i>Thryothorus ludovicianus</i></td> -</tr> -<tr> - <td class="tdl">Chimney swift</td> - <td class="tdl"><i>Chaetura pelagica</i></td> -</tr> -<tr> - <td class="tdl">Chipping sparrow</td> - <td class="tdl"><i>Spizella passerina</i></td> -</tr> -<tr> - <td class="tdl">Chuck-wills-widow</td> - <td class="tdl"><i>Caprimulgus carolinensis</i></td> -</tr> -<tr> - <td class="tdl">Clark's nutcracker</td> - <td class="tdl"><i>Nucifraga columbiana</i></td> -</tr> -<tr> - <td class="tdl">Cliff swallow</td> - <td class="tdl"><i>Petrochelidon pyrrhonota</i></td> -</tr> -<tr> - <td class="tdl">Common tern</td> - <td class="tdl"><i>Sterna hirundo</i></td> -</tr> -<tr> - <td class="tdl">Cooper's hawk</td> - <td class="tdl"><i>Accipiter cooperi</i></td> -</tr> -<tr> - <td class="tdl">Coot [American]</td> - <td class="tdl"><i>Fulica americana</i></td> -</tr> -<tr> - <td class="tdl">Cowbird</td> - <td class="tdl"><i>Molothrus ater</i></td> -</tr> -<tr> - <td class="tdl">Crossbill</td> - <td class="tdl"><i>Loxia curvirostra</i></td> -</tr> -<tr> - <td class="tdl">Crow</td> - <td class="tdl"><i>Corvus brachyrhynchos</i></td> -</tr> -<tr> - <td class="tdl">Duck hawk [peregrine falcon]</td> - <td class="tdl"><i>Falco peregrinus</i></td> -</tr> -<tr> - <td class="tdl">Eastern fox sparrow</td> - <td class="tdl"><i>Passerella iliaca iliaca</i></td> -</tr> -<tr> - <td class="tdl">Eider</td> - <td class="tdl"><i>Somateria mollissima</i></td> -</tr> -<tr> - <td class="tdl">Emperor goose</td> - <td class="tdl"><i>Philacte canagica</i></td> -</tr> -<tr> - <td class="tdl">Evening grosbeak</td> - <td class="tdl"><i>Hesperiphona vespertina</i></td> -</tr> -<tr> - <td class="tdl">European blackbird</td> - <td class="tdl"><i>Turdus merula merula</i></td> -</tr> -<tr> - <td class="tdl">Field sparrow</td> - <td class="tdl"><i>Spizella pusilla</i></td> -</tr> -<tr> - <td class="tdl">Forster's tern</td> - <td class="tdl"><i>Sterna forsteri</i></td> -</tr> -<tr> - <td class="tdl">Frigate [man-o'-war] bird</td> - <td class="tdl"><i>Fregata magnificens</i></td> -</tr> -<tr> - <td class="tdl">Golden-crowned kinglet</td> - <td class="tdl"><i>Regulus satrapa</i></td> -</tr> -<tr> - <td class="tdl">Golden plover</td> - <td class="tdl"><i>Pluvialis apricaria</i></td> -</tr> -<tr> - <td class="tdl">Golden-winged warbler</td> - <td class="tdl"><i>Vermivora chrysoptera</i></td> -</tr> -<tr> - <td class="tdl">Goshawk</td> - <td class="tdl"><i>Accipiter gentilis</i></td> -</tr> -<tr> - <td class="tdl">Grackle</td> - <td class="tdl"><i>Quiscalus quiscula</i></td> -</tr> -<tr> - <td class="tdl">Gray-cheeked thrush</td> - <td class="tdl"><i>Hylocichla minima</i></td> -</tr> -<tr> - <td class="tdl">Greenland wheatear</td> - <td class="tdl"><i>Oenanthe oenanthe leucorhoa</i></td> -</tr> -<tr> - <td class="tdl">Harris's sparrow</td> - <td class="tdl"><i>Zonotrichia querula</i></td> -</tr> -<tr> - <td class="tdl">Hermit thrush</td> - <td class="tdl"><i>Hylocichla guttata</i></td> -</tr> -<tr> - <td class="tdl">Herring gull</td> - <td class="tdl"><i>Larus argentatus</i></td> -</tr> -<tr> - <td class="tdl">Horned lark</td> - <td class="tdl"><i>Eremophila alpestris</i></td> -</tr> -<tr> - <td class="tdl">Horned owl</td> - <td class="tdl"><i>Bubo virginianus</i></td> -</tr> -<tr> - <td class="tdl">House finch</td> - <td class="tdl"><i>Carpodacus mexicanus</i></td> -</tr> -<tr> - <td class="tdl">Ipswich sparrow</td> - <td class="tdl"><i>Passerculus princeps</i></td> -</tr> -<tr> - <td class="tdl">Jacksnipe [see Wilson's snipe]</td> - <td class="tdl"><i>Capella gallinago delicata</i></td> -</tr> -<tr> - <td class="tdl">Junco - <span class="pagenum" id="Page_89">-89-</span></td> - <td class="tdl"><i>Junco hyemalis</i></td> -</tr> -<tr> - <td class="tdl">Kentucky warbler</td> - <td class="tdl"><i>Oporonis formosus</i></td> -</tr> -<tr> - <td class="tdl">Kingbird</td> - <td class="tdl"><i>Tyrannus tyrannus</i></td> -</tr> -<tr> - <td class="tdl">Knot</td> - <td class="tdl"><i>Calidris canutus</i></td> -</tr> -<tr> - <td class="tdl">Kodiak fox sparrow</td> - <td class="tdl"><i>Passerella iliaca hyperborea</i></td> -</tr> -<tr> - <td class="tdl">Lapland longspur</td> - <td class="tdl"><i>Calcarius lapponicus</i></td> -</tr> -<tr> - <td class="tdl">Lapwing</td> - <td class="tdl"><i>Vanellus vanellus</i></td> -</tr> -<tr> - <td class="tdl">Lesser yellowlegs</td> - <td class="tdl"><i>Totanus flavipes</i></td> -</tr> -<tr> - <td class="tdl">Little blue heron</td> - <td class="tdl"><i>Florida caerulea</i></td> -</tr> -<tr> - <td class="tdl">Loggerhead shrike</td> - <td class="tdl"><i>Lanius ludovicianus</i></td> -</tr> -<tr> - <td class="tdl">Long-billed marsh wren</td> - <td class="tdl"><i>Telmatodytes palustris</i></td> -</tr> -<tr> - <td class="tdl">Mallard</td> - <td class="tdl"><i>Anas platyrhynchos</i></td> -</tr> -<tr> - <td class="tdl">Maryland yellowthroat</td> - <td class="tdl"><i>Geothlypis trichas trichas</i></td> -</tr> -<tr> - <td class="tdl">Meadowlark</td> - <td class="tdl"><i>Sturnella magna</i></td> -</tr> -<tr> - <td class="tdl">Migratory quail</td> - <td class="tdl"><i>Coturnix coturnix</i></td> -</tr> -<tr> - <td class="tdl">Mockingbird</td> - <td class="tdl"><i>Mimus polyglottos</i></td> -</tr> -<tr> - <td class="tdl">Mourning dove</td> - <td class="tdl"><i>Zenaidura macroura</i></td> -</tr> -<tr> - <td class="tdl">Myrtle warbler</td> - <td class="tdl"><i>Dendroica coronata</i></td> -</tr> -<tr> - <td class="tdl">Nighthawk</td> - <td class="tdl"><i>Chordeilies minor</i></td> -</tr> -<tr> - <td class="tdl">Noddy tern</td> - <td class="tdl"><i>Amous stolidus</i></td> -</tr> -<tr> - <td class="tdl">Northern phalarope</td> - <td class="tdl"><i>Lobipes lobatus</i></td> -</tr> -<tr> - <td class="tdl">Northern robin</td> - <td class="tdl"><i>Turdus migratorius migratorius</i></td> -</tr> -<tr> - <td class="tdl">Orchard oriole</td> - <td class="tdl"><i>Icterus spurius</i></td> -</tr> -<tr> - <td class="tdl">Ovenbird</td> - <td class="tdl"><i>Seiurus aurocapillus</i></td> -</tr> -<tr> - <td class="tdl">Pacific [American] golden plover</td> - <td class="tdl"><i>Pluvialis dominica fulva</i></td> -</tr> -<tr> - <td class="tdl">Parasitic jaeger</td> - <td class="tdl"><i>Stercorarius parasiticus</i></td> -</tr> -<tr> - <td class="tdl">Peregrine falcon [duck hawk]</td> - <td class="tdl"><i>Falco peregrinus</i></td> -</tr> -<tr> - <td class="tdl">Pine Grosbeak</td> - <td class="tdl"><i>Pinicola enucleator</i></td> -</tr> -<tr> - <td class="tdl">Pine warbler</td> - <td class="tdl"><i>Dendroica pinus</i></td> -</tr> -<tr> - <td class="tdl">Pintail</td> - <td class="tdl"><i>Anas acuta tzitzihoa</i></td> -</tr> -<tr> - <td class="tdl">Pipit</td> - <td class="tdl"><i>Anthus spinoletta</i></td> -</tr> -<tr> - <td class="tdl">Poor-will</td> - <td class="tdl"><i>Phalaenoptilus nuttallii</i></td> -</tr> -<tr> - <td class="tdl">Purple finch</td> - <td class="tdl"><i>Carpodacus purpureus</i></td> -</tr> -<tr> - <td class="tdl">Purple martin</td> - <td class="tdl"><i>Progne subis</i></td> -</tr> -<tr> - <td class="tdl">Purple sandpiper</td> - <td class="tdl"><i>Erolia maritima</i></td> -</tr> -<tr> - <td class="tdl">Raven</td> - <td class="tdl"><i>Corvus corax</i></td> -</tr> -<tr> - <td class="tdl">Red-eyed vireo</td> - <td class="tdl"><i>Vireo olivaceus</i></td> -</tr> -<tr> - <td class="tdl">Redhead</td> - <td class="tdl"><i>Aythya americana</i></td> -</tr> -<tr> - <td class="tdl">Red-legged kittiwake - <span class="pagenum" id="Page_90">-90-</span></td> - <td class="tdl"><i>Rissa brevirostris</i></td> -</tr> -<tr> - <td class="tdl">Redpoll</td> - <td class="tdl"><i>Acanthis flammea</i></td> -</tr> -<tr> - <td class="tdl">Redstart</td> - <td class="tdl"><i>Setophaga ruticilla</i></td> -</tr> -<tr> - <td class="tdl">Red-tailed hawk</td> - <td class="tdl"><i>Buteo jamaicensis</i></td> -</tr> -<tr> - <td class="tdl">Red-winged blackbird</td> - <td class="tdl"><i>Agelaius phoeniceus</i></td> -</tr> -<tr> - <td class="tdl">Robin</td> - <td class="tdl"><i>Turdus migratorius</i></td> -</tr> -<tr> - <td class="tdl">Rock wren</td> - <td class="tdl"><i>Salpinctes obsoletus</i></td> -</tr> -<tr> - <td class="tdl">Rose-breasted grosbeak</td> - <td class="tdl"><i>Pheucticus ludovicianus</i></td> -</tr> -<tr> - <td class="tdl">Ross's goose</td> - <td class="tdl"><i>Chen rossi</i></td> -</tr> -<tr> - <td class="tdl">Ross's gull</td> - <td class="tdl"><i>Rhodostethia rosea</i></td> -</tr> -<tr> - <td class="tdl">Rosy finch</td> - <td class="tdl"><i>Leucosticte tephrocotis</i></td> -</tr> -<tr> - <td class="tdl">Rough-legged hawk</td> - <td class="tdl"><i>Buteo lagopus</i></td> -</tr> -<tr> - <td class="tdl">Ruby-throated hummingbird</td> - <td class="tdl"><i>Archilochus colubris</i></td> -</tr> -<tr> - <td class="tdl">Ruffed grouse</td> - <td class="tdl"><i>Bonasa umbellus</i></td> -</tr> -<tr> - <td class="tdl">Rusty blackbird</td> - <td class="tdl"><i>Euphagus carolinus</i></td> -</tr> -<tr> - <td class="tdl">Sanderling</td> - <td class="tdl"><i>Crocethia alba</i></td> -</tr> -<tr> - <td class="tdl">Scarlet tanager</td> - <td class="tdl"><i>Piranga olivacea</i></td> -</tr> -<tr> - <td class="tdl">Scaup</td> - <td class="tdl"><i>Aythya marila</i></td> -</tr> -<tr> - <td class="tdl">Screech owl</td> - <td class="tdl"><i>Otus asio</i></td> -</tr> -<tr> - <td class="tdl">Sharp-shinned hawk</td> - <td class="tdl"><i>Accipiter striatus</i></td> -</tr> -<tr> - <td class="tdl">Shumagin fox sparrow</td> - <td class="tdl"><i>Passerella iliaca unalaschensis</i></td> -</tr> -<tr> - <td class="tdl">Slate-colored junco</td> - <td class="tdl"><i>Junco hyemalis</i></td> -</tr> -<tr> - <td class="tdl">Snow bunting</td> - <td class="tdl"><i>Plectrophenax nivalis</i></td> -</tr> -<tr> - <td class="tdl">Snow goose</td> - <td class="tdl"><i>Chen hyperborea</i></td> -</tr> -<tr> - <td class="tdl">Snowy heron</td> - <td class="tdl"><i>Leucophoyx thula</i></td> -</tr> -<tr> - <td class="tdl">Snowy owl</td> - <td class="tdl"><i>Nyctea scandiaca</i></td> -</tr> -<tr> - <td class="tdl">Song sparrow</td> - <td class="tdl"><i>Melospiza melodia</i></td> -</tr> -<tr> - <td class="tdl">Sooty fox sparrow</td> - <td class="tdl"><i>Passerella iliaca fuliginosa</i></td> -</tr> -<tr> - <td class="tdl">Sooty tern</td> - <td class="tdl"><i>Sterna fuscata</i></td> -</tr> -<tr> - <td class="tdl">Sora or Carolina rail</td> - <td class="tdl"><i>Porzana Carolina</i></td> -</tr> -<tr> - <td class="tdl">Southern robin</td> - <td class="tdl"><i>Turdus migratorius achrusterus</i></td> -</tr> -<tr> - <td class="tdl">Starling</td> - <td class="tdl"><i>Sturnus vulgaris</i></td> -</tr> -<tr> - <td class="tdl">Swainson's hawk</td> - <td class="tdl"><i>Buteo swainsoni</i></td> -</tr> -<tr> - <td class="tdl">Swamp sparrow</td> - <td class="tdl"><i>Melospiza georgiana</i></td> -</tr> -<tr> - <td class="tdl">Townsend's fox sparrow</td> - <td class="tdl"><i>Passerella iliaca townsendi</i></td> -</tr> -<tr> - <td class="tdl">Tree sparrow</td> - <td class="tdl"><i>Spizella arborea</i></td> -</tr> -<tr> - <td class="tdl">Tufted titmouse</td> - <td class="tdl"><i>Parus bicolor</i></td> -</tr> -<tr> - <td class="tdl">Turkey vulture</td> - <td class="tdl"><i>Cathartes aura</i></td> -</tr> -<tr> - <td class="tdl">Turnstone</td> - <td class="tdl"><i>Arenaria interpres</i></td> -</tr> -<tr> - <td class="tdl">Upland plover [Bartramian sandpiper] - <span class="pagenum" id="Page_91">-91-</span></td> - <td class="tdl"><i>Bartramia longicauda</i></td> -</tr> -<tr> - <td class="tdl">Valdez fox sparrow</td> - <td class="tdl"><i>Passerella iliaca sinuosa</i></td> -</tr> -<tr> - <td class="tdl">Vesper sparrow</td> - <td class="tdl"><i>Pooecetes gramineus</i></td> -</tr> -<tr> - <td class="tdl">Western palm warbler</td> - <td class="tdl"><i>Dendroica palmarum palmarum</i></td> -</tr> -<tr> - <td class="tdl">Western tanager</td> - <td class="tdl"><i>Piranga ludoviciana</i></td> -</tr> -<tr> - <td class="tdl">Western wood pewee</td> - <td class="tdl"><i>Contopus richardsonii</i></td> -</tr> -<tr> - <td class="tdl">White-breasted nuthatch</td> - <td class="tdl"><i>Sitta carolinensis</i></td> -</tr> -<tr> - <td class="tdl">White-throated sparrow</td> - <td class="tdl"><i>Zonotrichia albicollis</i></td> -</tr> -<tr> - <td class="tdl">White-winged scoter</td> - <td class="tdl"><i>Melanitta fusca</i></td> -</tr> -<tr> - <td class="tdl">Widgeon</td> - <td class="tdl"><i>Mareca americana</i></td> -</tr> -<tr> - <td class="tdl">Williamson's sapsucker</td> - <td class="tdl"><i>Sphyrapicus thyroideus</i></td> -</tr> -<tr> - <td class="tdl">Wilson's [common] snipe</td> - <td class="tdl"><i>Capella gallinago delicata</i></td> -</tr> -<tr> - <td class="tdl">Winter wren</td> - <td class="tdl"><i>Troglodytes troglodytes</i></td> -</tr> -<tr> - <td class="tdl">Woodcock</td> - <td class="tdl"><i>Scolopax rusticola</i></td> -</tr> -<tr> - <td class="tdl">Wood thrush</td> - <td class="tdl"><i>Hylocichla mustelina</i></td> -</tr> -<tr> - <td class="tdl">Worm-eating warbler</td> - <td class="tdl"><i>Helmitheros vermivorus</i></td> -</tr> -<tr> - <td class="tdl">Wrentit</td> - <td class="tdl"><i>Chamaea fasciata</i></td> -</tr> -<tr> - <td class="tdl">Yakutat fox sparrow</td> - <td class="tdl"><i>Passerella iliaca annectens</i></td> -</tr> -<tr> - <td class="tdl">Yellow-billed cuckoo</td> - <td class="tdl"><i>Coccyzus americanus</i></td> -</tr> -<tr> - <td class="tdl">Yellow-billed loon</td> - <td class="tdl"><i>Gavia adamsii</i></td> -</tr> -<tr> - <td class="tdl">Yellow-headed blackbird</td> - <td class="tdl"><i>Xanthocephalus xanthocephalus</i></td> -</tr> -<tr> - <td class="tdl">Yellow palm warbler</td> - <td class="tdl"><i>Dendroica palmarum hypochrysea</i></td> -</tr> -<tr> - <td class="tdl">Yellow warbler</td> - <td class="tdl"><i>Dendroica petechia</i></td> -</tr> -</table> - - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_92">-92-</span></p> - -<h2 class="nobreak" id="Appendix_II">Appendix II—<i>Bird Banding</i></h2> -</div> - - -<p>Frequent reference has been made in this bulletin to bird banding as -a means for obtaining information on the migrations and life histories -of birds. Since 1920 this work in North America has been under the -direction of the Fish and Wildlife Service in cooperation with the -Dominion Wildlife Service of Canada. Each year birds to the number -of a quarter of a million or more may be marked with numbered bands.</p> - -<p>As anyone interested in birds, either game or nongame, may have -a marked individual come into his hands, there are several pertinent -details that should be remembered if the recovery record is to have -maximum value in advancing the science of ornithology.</p> - -<p>1. The reporting letter should be addressed to: Bird Banding Office, -Patuxent Research Refuge, Fish and Wildlife Service, Laurel, Md.</p> - -<p>2. In the letter print the full number of the band, including the -series designation and the serial number. The series designation may -be a single letter or a two- or three-digit number and may be stamped -to the left or over the serial number. The series designation, if a number -such as "48" or "50," is not a date and should not be so interpreted. -Full numbers are correctly written as: A-678901; 48-345920; 141-543678; -20-167; 496-00517; etc.</p> - -<p>3. If the bird is alive and uninjured, read the number carefully without -removing the band, and release the bird. It may be reported again. -If it is dead, remove the band and, after flattening it out, attach it to -the letter with scotch tape or surgical adhesive tape. Should it be -desired as a souvenir, it will be returned upon request.</p> - -<p>4. Give in the report the exact date, the location (town, county, -State, etc.) and the manner in which the bird was obtained, that is, -whether it was shot, found dead, trapped, etc.</p> - -<p>5. Print your own name and permanent address clearly on the -letter.</p> - -<p>6. Keep a record of the band number and refer to it should there -be any subsequent correspondence about it with the Service. The -number is always the clue to any record of a banded bird.</p> - -<p>Some bands may bear the inscription "Notify F. and Wildlife Service, -Washington, D. C." or "Notify Biological Survey, Washington, -D. C.," and on the smaller sizes these may be abbreviated to "F. and -W. Serv. Wash. D. C." or "Biol. Surv. Wash. D. C."</p> - -<p><span class="pagenum" id="Page_93">-93-</span></p> - -<p>All reports of the recovery of banded birds will be acknowledged -with the name of the bird, the date and place where it was banded, -and the name and address of the bander.</p> - -<p>The banding of birds is done by regular officers of the United States -and Dominion Services, by biologists and technicians of the States and -Provinces, and by volunteer cooperators who are specially licensed -under the provisions of the Migratory Bird Treaty Act. The banding -of migratory waterfowl is largely restricted to Federal and State officers -and is done chiefly in refuge areas. Most nongame birds are -banded by volunteer cooperators who are scattered over the United -States, Canada, and Alaska. The bands are furnished without charge -by the Service but each station operator supplies his own traps and -other equipment.</p> - -<p>To participate in this work, certain rules must be adhered to. Applicants -for banding permits:</p> - -<p>1. Must be at least 18 years of age.</p> - -<p>2. Must be thoroughly competent to identify positively all local -birds.</p> - -<p>3. Must have their ability vouched for by three recognized ornithologists -or by other banders.</p> - -<p>Application blanks for the Federal permits required may be obtained -from the Bird Banding Office, Patuxent Research Refuge, Fish and -Wildlife Service, Laurel, Md., or, in Canada, from the Chief, Dominion -Wildlife Service, Ottawa, Ontario.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_94">-94-</span></p> - -<h2 class="nobreak" id="Bibliography"><i>Bibliography</i></h2> -</div> - - -<p>Since almost every faunal paper on birds has a bearing on the subject of migration, -only a few can be listed in this publication. Those included were selected -to aid the student wishing to pursue the subject further and to cover not only all -cited in the text but also others consulted and used in its preparation.</p> - -<p><span class="smcap">Allard, H. A.</span></p> - -<div class="blockquot"> - -<p>1928. Bird migration from the point of view of light and length of day -changes. Am. Naturalist 62, pp. 385-408.</p> -</div> - -<p><span class="smcap">Austin, O. L., Jr.</span></p> - -<div class="blockquot"> - -<p>1928. Migration-routes of the Arctic tern (<i>Sterna paradisaea</i> Brunnich). -Northeastern Bird Banding Assn. Bull., vol, 4, pp. 121-125.</p> -</div> - -<p><span class="smcap">Baird, S. F.</span></p> - -<div class="blockquot"> - -<p>1866. The distribution and migration of North American birds. Am. Jour. -Sci., vol. 41, pp. 78-90, 184-192, 337-347.</p> -</div> - -<p><span class="smcap">Bergtold, W. H.</span></p> - -<div class="blockquot"> - -<p>1926. Avian gonads and migration. The Condor, vol. 28, pp. 114-120.</p> -</div> - -<p><span class="smcap">Bissonette, Thomas Hume</span></p> - -<div class="blockquot"> - -<p>1936. Normal progressive changes in the ovary of the starling (<i>Sturnus vulgaris</i>) -from December to April. The Auk, vol. 53, pp. 31-50, illus.</p> - -<p>1939. Sexual photoperiodicity in the blue jay (<i>Cyanocitta cristata</i>). Wilson -Bull., vol. 51, pp. 227-232, pis. 9-11.</p> -</div> - -<p><span class="smcap">Clark, Austin H.</span></p> - -<div class="blockquot"> - -<p>1925. Animal flight. Sci. Monthly, vol. 20, pp. 5-20. -Clarke, W. E.</p> - -<p>1912. Studies in bird migration. 2 vol., illus. London. -Cooke, May Thacher</p> - -<p>1937. Flight speed of birds. U. S. Dept. Agr. Cir. 428, 13 pp.</p> - -<p>1945. Transoceanic recoveries of banded birds. Bird-Banding, vol. 16, No. 4, -pp. 123-129.</p> -</div> - -<p><span class="smcap">Cooke, W. W.</span></p> - -<div class="blockquot"> - -<p>1888. Report on bird migration in the Mississippi Valley in the -years 1884 and 1885. U. S. Dept. Agr., Div. Econ. Ornith. Bull. -2, 313 pp., illus.</p> - -<p>1904. Distribution and migration of North American warblers. U. S. -Dept. Agr., Div. Biol. Survey Bull. 18, 142 pp.</p> - -<p>1904. The effect of altitude on bird migration. The Auk, vol. 21, -pp. 338-341.</p> - -<p>1905a. Routes of bird migration. The Auk, vol. 22, pp. 1-11.</p> - -<p>1905b. The winter ranges of the warblers (<i>Mniotiltidae</i>). The Auk, -vol. 22, pp. 296-299.</p> - -<p>1906. Distribution and migration of North American ducks, geese, -and swans. U. S. Dept. Agr., Bur. Biol. Survey Bull, 26, 90 pp.</p> - -<p>1908. Averaging migration dates. The Auk, vol. 25, pp. 485-486.</p> - -<p>1910. Distribution and migration of North American shore birds. U. -S. Dept. Agr., Bur. Biol. Survey Bull. 35, 100 pp., illus.</p> - -<p>1913a. Distribution and migration of North American herons and -their allies. U. S. Dept. Agr., Bur. Biol. Survey Bull. 45, 70 -pp., illus.</p> - -<p>1913b. The relation of bird migration to the weather. The Auk, vol. -30, pp. 205-221, illus.</p> - -<p>1914. Distribution and migration of North American rails and -their allies. U. S. Dept. Agr. Bull. 128, 50 pp. illus,</p> -</div> - -<p><span class="pagenum" id="Page_95">-95-</span></p> - -<div class="blockquot"> - -<p>1915a. Bird migration. U. S. Dept. Agr. Bull. 185, 47 pp., illus.</p> - -<p>1915b. Bird migration in the Mackenzie Valley. The Auk, vol. 32, pp. -442-459, illus.</p> - -<p>1915c. Distribution and migration of North American gulls and their allies. -U. S. Dept. Agr. Bull. 292, 70 pp., illus.</p> - -<p>1915d. The yellow-billed loon: A problem in migration. The Condor, vol. -17, pp. 213-214.</p> -</div> - -<p><span class="smcap">Coues, E.</span></p> - -<div class="blockquot"> - -<p>1878. Birds of the Colorado Valley, a repository of scientific and popular -information concerning North American ornithology. U. S. Dept. Interior -Misc. Pub. II, 807 pp., illus.</p> -</div> - -<p><span class="smcap">DeLury, Ralph E.</span></p> - -<div class="blockquot"> - -<p>1938. Sunspot Influences. Jour. Royal Astron. Soc. of Can., pt. 1, March -1938, pt. 2, April 1938, 50 pp.</p> -</div> - -<p><span class="smcap">Dixon, Joseph</span></p> - -<div class="blockquot"> - -<p>1916. Migration of the yellow-billed loon. The Auk, vol. 33, No. 4, pp. -370-376.</p> -</div> - -<p><span class="smcap">Eaton, Richard Jefferson</span></p> - -<div class="blockquot"> - -<p>1933-34. The migratory movements of certain colonies of herring gulls. -Bird-Banding, vol. 4, No. 4, pp. 165-176; vol. 5, No. 1, pp. 1-19; vol. 5, -No. 2, pp. 70-84.</p> -</div> - -<p><span class="smcap">Earner, Donald S.</span></p> - -<div class="blockquot"> - -<p>1945. The return of robins to their birthplaces. Bird-Banding, vol. 16, No. -3, pp. 81-99.</p> -</div> - -<p><span class="smcap">Furlong, W. R.</span></p> - -<div class="blockquot"> - -<p>1933. Land-birds in a gale at sea. Bird Lore, vol. 35, No. 5, pp. 263-265.</p> -</div> - -<p><span class="smcap">Gätke, H.</span></p> - -<div class="blockquot"> - -<p>1895. Heligoland as an ornithological observatory, the results of fifty years' -experience. (Transl. from the German by R. Rosenstock). 599 pp., illus. -Edinburgh.</p> -</div> - -<p><span class="smcap">Gordon, Donald A.</span></p> - -<div class="blockquot"> - -<p>1948. Some considerations of bird migration: continental drift and bird -migration. Science, vol. 108, pp. 705-711.</p> -</div> - -<p><span class="smcap">Griffin, Donald R.</span></p> - -<div class="blockquot"> - -<p>1940. Homing experiments with Leach's petrels. The Auk, vol. 57, No. 1, -pp. 61-74.</p> - -<p>1943. Homing experiments with herring gulls and common terns. Bird-Banding, -vol. 14, No. 1 and 2, pp. 7-33.</p> - -<p>1944. The sensory basis of bird navigation. Quart. Rev. of Biol., vol. 19, -No. 1, pp. 15-31.</p> -</div> - -<p><span class="smcap">Grinnell, J.</span></p> - -<div class="blockquot"> - -<p>1931. Some angles in the problem of bird migration. The Auk, vol. 48, -pp. 22-32.</p> -</div> - -<p><span class="smcap">Gross, A. O.</span></p> - -<div class="blockquot"> - -<p>1927. The snowy owl migration of 1926-27. The Auk, vol. 44, pp. 479-493, -illus.</p> - -<p>1947. Cyclic invasions of the snowy owl and the migration of 1945-46. The -Auk, vol. 64, No. 4, pp. 584-601.</p> -</div> - -<p><span class="smcap">Harrison, T. H.</span></p> - -<div class="blockquot"> - -<p>1931. On the normal flight speeds of birds. Brit. Birds, vol. 25, pp. 86-96. -Jaeger, Edmund C.</p> - -<p>1948. Does the poor-will "hibernate"? The Condor, vol. 50, p. 45.</p> - -<p>1949. Further observations on the hibernation of the poor-will. The Condor, -vol. 51, pp. 105-109.</p> -</div> - -<p><span class="pagenum" id="Page_96">-96-</span></p> - -<p><span class="smcap">Lewis, Harrison F.</span></p> - -<div class="blockquot"> - -<p>1937. Migrations of the American brant (<i>Branta bernicla hrota</i>). The Auk, -vol. 54, pp. 73-95.</p> -</div> - -<p><span class="smcap">Lincoln, F. C.</span></p> - -<div class="blockquot"> - -<p>1917. Bohemian waxwing (<i>Bombycilla garrula</i>) in Colorado. The Auk, -vol. 34, p. 341.</p> - -<p>1922. Trapping ducks for banding purposes: with an account of the results -obtained from one waterfowl station. The Auk, vol. 39, pp. 322-334, illus.</p> - -<p>1924a. Banding notes on the migration of the pintail. The Condor, vol. 26, -pp. 88-90.</p> - -<p>1924b. Returns from banded birds, 1920 to 1923, U. S. Dept. Agr. Bull.</p> - -<p>1268, 56 pp., illus.</p> - -<p>1926. The migration of the cackling goose. The Condor, vol. 28, pp. 153-157, -illus.</p> - -<p>1927a. Notes on the migration of young common terns. Northeastern Bird -Banding Assoc. Bull., vol. 3, pp. 23-28, illus.</p> - -<p>1927b. Returns from banded birds, 1923 to 1926. U. S. Dept. Agr. Tech. -Bull. No. 32, 95 pp., illus.</p> - -<p>1928. The migration of young North American herring gulls. The Auk, -vol. 45, pp. 49-59.</p> - -<p>1934a. Distribution and migration of the redhead (<i>Nyroca americana</i>). -Trans. 20th Am. Game Conf., pp. 280-287, map.</p> - -<p>1934b. The operation of homing instinct. Bird-Banding, vol. 5, No. 4, pp. -149-155.</p> - -<p>1935a. Ancestral highways of the sky. American Forests, vol. 41, No. 4, -pp. 157, 159, and 196, 4 figs.</p> - -<p>1935b. The migration of North American birds. U. S. Dept. Agr. Cir. -363, 72 pp., 29 figs., bibliog.</p> - -<p>1935c. The waterfowl flyways of North America. U. S. Dept. Agr, Cir. -342, 12 pp., illus.</p> - -<p>1936. Trans-Atlantic flight of gull-billed tern. The Auk, vol. 53, No. 3,</p> - -<p>1937a. The enigma of bird migration. Sci. Digest, vol. 1. No. 5, pp. 63-65.</p> - -<p>1937b. Our greatest travelers. In "The Book of Birds," Nat. Geog. Soc, -vol. 2, pp. 301-350, 1937.</p> - -<p>1939a. The migration of American birds. Doubleday, Doran & Co., New -York, pp. i-xii and 1-189, col. pl. i-xii, maps 1-22.</p> - -<p>1939b. The individual vs. the species in migration studies. The Auk, vol. -56, No. 3, pp. 250-254.</p> - -<p>1940. When the dove travels. Outdoor Georgia, vol. 1. No. 4, pp. 9 and -22 (1 map).</p> - -<p>1941. The waterfowl flyways. "Wild Ducks," Am. Wildlife Inst., pp. 20-29.</p> - -<p>1942a. La migración de aves en el Hemisferio Occidental. Pub. and dist. -by Panam. Sec. of the Int. Comm. for the Protection of Birds. Pp. 1-12, -illus. (maps). Both Spanish and English versions.</p> - -<p>1942b. Migration routes and flyways. In "Ducks, Geese and Swans of -North America," by Francis H. Kortright, Am. Wildlife Inst., pp. 47-53.</p> - -<p>1944a. Regulation by flyways. Am. Rifleman, vol. 92, No. 11, pp. 21-23, 26, -illus. (3 maps).</p> - -<p>1944b. Chimney swift winter range discovered. The Auk, vol. 61, No. 4, -pp. 604-609, map.</p> - -<p>1945a. The mourning dove as a game bird. Fish and Wildlife Serv. Cir. -10, pp. 1-8, illus.</p> - -<p>1945b. Flyway regulations. Trans. 10th N. A. Wildlife Conf., pp. 50-51.</p> -</div> - -<p><span class="pagenum" id="Page_97">-97-</span></p> - -<div class="blockquot"> - -<p>1946. Keeping up with the waterfowl. Audubon Mag., vol. 48, No. 3, pp. -194-205, 7 illus., 10 maps. Reprinted as Fish and Wildlife Serv. Leaflet -294, April 1947, pp. 1-10.</p> - -<p>1949. The Mississippi flyway. Lead-off chapter in "Wildfowling in the -Mississippi Flyway" ed. by Eugene V. Connett, D. Van Nostrand Co., -New York, pp. 1-18, map, 12 photos.</p> -</div> - -<p><span class="smcap">Lowery, George H.</span></p> - -<div class="blockquot"> - -<p>1945, Trans-Gulf spring migration of birds and the coastal hiatus. Wilson -Bull., vol. 57, No. 2, pp. 92-121, pis. 9, 10.</p> - -<p>1946. Evidence of trans-Gulf migration. The Auk, vol. 63, No. 2, pp. -175-211.</p> -</div> - -<p><span class="smcap">McMillan, Neil T.</span></p> - -<div class="blockquot"> - -<p>1938. Birds and the wind. Bird Lore, vol. 40, No. 6, 3 plates. Reprinted -Smithsonian Kept, for 1939, pp. 355-363.</p> -</div> - -<p><span class="smcap">Magee, M. J.</span></p> - -<div class="blockquot"> - -<p>1928. Evening grosbeak recoveries. Northeastern Bird Banding Assoc. Bull., -vol. 4, pp. 56-59.</p> -</div> - -<p><span class="smcap">Main, John S.</span></p> - -<div class="blockquot"> - -<p>1932. The influence of temperature on migration. Wilson Bull., vol. 44, -pp. 10-12.</p> -</div> - -<p><span class="smcap">May, J. B.</span></p> - -<div class="blockquot"> - -<p>1929. Recoveries of black-crowned night herons banded in Massachusetts. -Northeastern Bird Banding Assoc. Bull., vol. 5, pp. 7-16, illus.</p> -</div> - -<p><span class="smcap">Palmén, J. A.</span></p> - -<div class="blockquot"> - -<p>1893. Report on the migration of birds. Transl. from the German by C. W. -Shoemaker. Smithsonian Inst. Ann. Rept., 1892, pp. 375-396, illus.</p> -</div> - -<p><span class="smcap">Phillips, J. C. and F. C. Lincoln</span></p> - -<div class="blockquot"> - -<p>1930. American waterfowl: their present situation and the outlook for their -future. Houghton Mifflin Co., Cambridge, Mass., pp. i-xv, 1-312, illus.</p> -</div> - -<p><span class="smcap">Pough, Richard H.</span></p> - -<div class="blockquot"> - -<p>1948. Out of the night sky. Audubon Mag., vol. 50, No. 6, pp. 354-355, -illus.</p> -</div> - -<p><span class="smcap">Rense, William A.</span></p> - -<div class="blockquot"> - -<p>1946. Astronomy and ornithology. Popular Astron., vol. 54, No. 2, pp. 1-19. -Robbins, Chandler S.</p> - -<p>1949. Weather and bird migration. The Wood Thrush, vol. 4, No. 4, pp. -130-144.</p> -</div> - -<p><span class="smcap">Rowan, W.</span></p> - -<div class="blockquot"> - -<p>1925. Relation of light to bird migration and developmental changes. Nature -[London] vol. 115, pp. 494-495.</p> - -<p>1926. On photoperiodism, reproductive periodicity, and the annual migrations -of birds and certain fishes. Boston Soc. Nat. Hist. Proc., vol. 38, pp. 147-189.</p> - -<p>1930a. Experiments in bird migration. II. Reversed migration. Nat. Acad. -Sci. Proc, vol. 16, p. 520-525.</p> - -<p>1930b. The mechanism of bird migration. Sci. Progress, vol. 25, pp. 70-78.</p> - -<p>1931. The riddle of migration. Williams & Wilkins, Baltimore, pp. i-xiv, -1-151, illus.</p> -</div> - -<p><span class="smcap">Snyder, L. L.</span></p> - -<div class="blockquot"> - -<p>1943. The snowy owl migration of 1941-42. Wilson Bull. vol. 55, No. i, -pp. 8-10.</p> -</div> - -<p><span class="smcap">Taverner, P. A.</span></p> - -<div class="blockquot"> - -<p>1935. Continental land masses and their effect upon bird life. The Condor, -vol. 37, pp. 160-162, 2 illus.</p> -</div> - -<p><span class="pagenum" id="Page_98">-98-</span></p> - -<p><span class="smcap">Warner, Lucien H.</span></p> - -<div class="blockquot"> - -<p>1931. The present status of the problems of orientation and homing by birds. -Quart. Rev. of Biol., vol. 6, No. 2, pp. 208-214.</p> -</div> - -<p>Watson, J. B., and K. S. Lashley</p> - -<div class="blockquot"> - -<p>1915. An historical and experimental study of homing. Carnegie Inst. Washington, -Dept. Marine Biol. Papers, vol. 7, pp. 1-60, illus.</p> -</div> - -<p><span class="smcap">Wetmore, A.</span></p> - -<div class="blockquot"> - -<p>1923. Migration records from wild ducks and other birds banded in the Salt -Lake Valley, Utah. U. S. Dept. Agr. Bull. 1145, 16 pp., illus.</p> - -<p>1926. The migration of birds. Harvard Univ. Press, Cambridge, Mass., -pp. i-viii, 1-217, illus.</p> - -<p>1932. Bird migration. Sci. Monthly, vol. 34, pp. 459-462.</p> -</div> - -<p>Williams, George G.</p> - -<div class="blockquot"> - -<p>1945. Do birds cross the Gulf of Mexico in Spring? The Auk, vol. 62, No. 1, -pp. 98-111, map.</p> - -<p>1947. Lowery on trans-Gulf migration. The Auk, vol. 64, No. 2, pp. 217-237.</p> -</div> - -<p><span class="smcap">Winkenwerder, H. A.</span></p> - -<div class="blockquot"> - -<p>1902. The migration of birds with special reference to nocturnal flight. Wisconsin -Nat. Hist. Soc. vol. 2 n. s. pp. 177-263, illus.</p> -</div> - -<p><span class="smcap">Wolfson, Albert</span></p> - -<div class="blockquot"> - -<p>1940. A preliminary report on some experiments on bird migration. The -Condor, vol. 42, No. 2, pp. 93-99.</p> - -<p>1945. The role of the pituitary, fat deposition, and body weight in bird migration. -The Condor, vol. 47, No. 3, pp. 95-127.</p> - -<p>1948. Bird migration and the concept of continental drift. Science, vol. 108, -No. 2793, pp. 23-30.</p> -</div> - -<p><span class="smcap">Woodbury, Angus M.</span></p> - -<div class="blockquot"> - -<p>1941. Animal migration—periodic response theory. The Auk, vol. 58, pp. -463-505.</p> -</div> - -<p><span class="smcap">Yeagley, Henry L.</span></p> - -<div class="blockquot"> - -<p>1947. A preliminary study of a physical basis of bird navigation. Jour. -Applied Physics, vol. 18, No. 12, pp. 1035-1063.</p> -</div> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_99">-99-</span></p> - -<h2 class="nobreak" id="Index"><i>Index</i></h2> -</div> - -<div class="tdc"> -[ <a href="#Alph_A">A</a> ] [ <a href="#Alph_B">B</a> ] [ <a href="#Alph_C">C</a> ] [ <a href="#Alph_D">D</a> ] [ <a href="#Alph_E">E</a> ] [ <a href="#Alph_F">F</a> ] [ <a href="#Alph_G">G</a> ] -[ <a href="#Alph_H">H</a> ] [ <a href="#Alph_I">I</a> ] [ <a href="#Alph_J">J</a> ] [ <a href="#Alph_K">K</a> ] [ <a href="#Alph_L">L</a> ]<br /> -[ <a href="#Alph_M">M</a> ] [ <a href="#Alph_N">N</a> ] -[ <a href="#Alph_O">O</a> ] [ <a href="#Alph_P">P</a> ] [ <a href="#Alph_Q">Q</a> ] [ <a href="#Alph_R">R</a> ] [ <a href="#Alph_S">S</a> ] [ <a href="#Alph_T">T</a> ] -[ <a href="#Alph_V">V</a> ] [ <a href="#Alph_W">W</a> ] [ <a href="#Alph_Y">Y</a> ] -</div> - - -<p class="p0"> -<a id="Alph_A"></a>Advantages of migration, <a href="#Page_6">6</a><br /> -Aerial obstructions, <a href="#Page_76">76</a><br /> -Altitudes of travel, <a href="#Page_26">26</a><br /> -Ancestral home theory, <a href="#Page_8">8</a><br /> -Arctic route, <a href="#Page_68">68</a><br /> -Aristotle, <a href="#Page_2">2</a>, <a href="#Page_4">4</a>, <a href="#Page_5">5</a><br /> -Atlantic coast route, <a href="#Page_53">53</a><br /> -Atlantic oceanic route, <a href="#Page_48">48</a><br /> -<br /> -<a id="Alph_B"></a>Baldpate, <a href="#Page_62">62</a><br /> -Banding studies, <a href="#Page_81">81</a>, <a href="#Page_92">92</a><br /> -Blackbird, <a href="#Page_32">32</a>, <a href="#Page_33">33</a>, <a href="#Page_60">60</a><br /> - Brewer's, <a href="#Page_32">32</a><br /> - European, <a href="#Page_4">4</a><br /> - red-winged, <a href="#Page_22">22</a>, <a href="#Page_32">32</a>, <a href="#Page_33">33</a>, <a href="#Page_35">35</a>, <a href="#Page_37">37</a><br /> - rusty, <a href="#Page_70">70</a><br /> - yellow-headed, <a href="#Page_32">32</a><br /> -Bluebird, <a href="#Page_9">9</a>, <a href="#Page_34">34</a>, <a href="#Page_37">37</a>, <a href="#Page_81">81</a><br /> -Bluethroat, <a href="#Page_19">19</a><br /> -Bobolink, <a href="#Page_32">32</a>, <a href="#Page_55">55</a>, <a href="#Page_56">56 (map)</a>, <a href="#Page_69">69</a>, <a href="#Page_70">70</a>, <a href="#Page_71">71</a><br /> -Bobwhite, <a href="#Page_32">32</a>, <a href="#Page_34">34</a>, <a href="#Page_82">82</a>, <a href="#Page_83">83</a><br /> -Brant, <a href="#Page_57">57</a>, <a href="#Page_58">58</a><br /> - Atlantic, <a href="#Page_57">57</a><br /> - Black, <a href="#Page_68">68</a><br /> -Bullbat, <a href="#Page_32">32</a><br /> -Bunting, snow, <a href="#Page_34">34</a><br /> -<br /> -<a id="Alph_C"></a>Canvasback, <a href="#Page_58">58</a><br /> -Cardinal, <a href="#Page_34">34</a>, <a href="#Page_82">82</a><br /> -Chickadee, <a href="#Page_7">7</a>, <a href="#Page_72">72</a><br /> - black-capped, <a href="#Page_83">83</a><br /> - Carolina, <a href="#Page_83">83</a><br /> -Chuck-wills-widow, <a href="#Page_55">55</a><br /> -Clarke, W. E., <a href="#Page_4">4</a>, <a href="#Page_6">6</a><br /> -Compsothlypidae, <a href="#Page_32">32</a><br /> -Conclusions, <a href="#Page_85">85</a><br /> -Continental drift, theory of, <a href="#Page_11">11</a><br /> -Coot, <a href="#Page_55">55</a><br /> -Coues, Elliott, <a href="#Page_4">4</a><br /> -Cowbird, <a href="#Page_29">29</a><br /> -Crane, <a href="#Page_2">2</a>, <a href="#Page_4">4</a>, <a href="#Page_6">6</a>, <a href="#Page_16">16</a>, <a href="#Page_26">26</a>, <a href="#Page_27">27</a>, <a href="#Page_28">28</a><br /> -Creeper, brown, <a href="#Page_75">75</a><br /> -Crossbill, <a href="#Page_7">7</a>, <a href="#Page_32">32</a>, <a href="#Page_74">74</a><br /> -Crow, <a href="#Page_20">20</a>, <a href="#Page_22">22</a>, <a href="#Page_32">32</a><br /> - Clark's, <a href="#Page_73">73</a><br /> -Cuckoo, black-billed, <a href="#Page_55">55</a><br /> - yellow-billed, <a href="#Page_55">55</a><br /> -<br /> -<a id="Alph_D"></a>Diurnal migration, <a href="#Page_15">15</a><br /> -Diving birds, <a href="#Page_16">16</a><br /> -Dove, <a href="#Page_4">4</a><br /> - mourning, <a href="#Page_19">19</a><br /> - turtle, <a href="#Page_2">2</a>, <a href="#Page_6">6</a><br /> -Duck, <a href="#Page_2">2</a>, <a href="#Page_15">15</a>, <a href="#Page_16">16</a>, <a href="#Page_19">19</a>, <a href="#Page_20">20</a>, <a href="#Page_21">21</a>, <a href="#Page_32">32</a>, <a href="#Page_33">33</a>, <a href="#Page_37">37</a>, <a href="#Page_42">42</a>, <a href="#Page_58">58</a>, <a href="#Page_60">60</a>, <a href="#Page_61">61</a>, <a href="#Page_62">62</a>, <a href="#Page_68">68</a><br /> - black, <a href="#Page_20">20</a>, <a href="#Page_33">33</a>, <a href="#Page_58">58</a>, <a href="#Page_61">61</a><br /> - eider, <a href="#Page_68">68</a><br /> - scaup, <a href="#Page_58">58</a><br /> - sea, <a href="#Page_59">59</a>, <a href="#Page_63">63</a><br /> -<br /> -<a id="Alph_E"></a>Eel, <a href="#Page_29">29</a><br /> -Egret, <a href="#Page_73">73</a><br /> -Eider, <a href="#Page_68">68</a><br /> -Evolution of migration routes, <a href="#Page_70">70</a><br /> -Exhaustion, <a href="#Page_78">78</a><br /> -<br /> -<a id="Alph_F"></a>Falcon, peregrine, <a href="#Page_19">19</a><br /> -Fall flights, <a href="#Page_37">37</a><br /> -Finch, <a href="#Page_43">43</a><br /> - house, <a href="#Page_82">82</a><br /> - purple, <a href="#Page_74">74</a><br /> - rosy, <a href="#Page_72">72</a><br /> -Fishes, <a href="#Page_29">29</a><br /> -Flicker, <a href="#Page_70">70</a><br /> -Flight speed, <a href="#Page_18">18</a><br /> -Flycatcher, <a href="#Page_15">15</a>, <a href="#Page_19">19</a>, <a href="#Page_31">31</a><br /> -Fly ways, <a href="#Page_46">46</a><br /> - Atlantic, <a href="#Page_49">49 (map)</a>, <a href="#Page_58">58</a><br /> - Mississippi, <a href="#Page_50">50 (map)</a><br /> - Central, <a href="#Page_51">51 (map)</a><br /> - Pacific, <a href="#Page_52">52 (map)</a><br /> -<br /> -<a id="Alph_G"></a>Gätke, Heinrich, <a href="#Page_19">19</a><br /> -Goose, <a href="#Page_2">2</a>, <a href="#Page_4">4</a>, <a href="#Page_15">15</a>, <a href="#Page_16">16</a>, <a href="#Page_19">19</a>, <a href="#Page_20">20</a>, <a href="#Page_21">21</a>, <a href="#Page_33">33</a>, <a href="#Page_59">59</a>, <a href="#Page_60">60</a>, <a href="#Page_61">61</a>, <a href="#Page_62">62</a><br /> - blue, <a href="#Page_22">22</a>, <a href="#Page_32">32</a>, <a href="#Page_61">61</a>, <a href="#Page_62">62</a><br /> - cackling, <a href="#Page_63">63</a><br /> - Canada, <a href="#Page_15">15</a>, <a href="#Page_21">21</a>, <a href="#Page_22">22 (map)</a>, <a href="#Page_32">32</a>, <a href="#Page_58">58</a>, <a href="#Page_59">59</a>, <a href="#Page_81">81</a><br /> - emperor, <a href="#Page_68">68</a><br /> - Ross's, <a href="#Page_64">64 (map)</a><br /> - snow, <a href="#Page_32">32</a>, <a href="#Page_72">72</a><br /> -Gordon, Donald A., <a href="#Page_30">30</a><br /> -Goshawk, <a href="#Page_12">12</a><br /> -Grackle, <a href="#Page_37">37</a><br /> -<span class="pagenum" id="Page_100">-100-</span> - bronzed, <a href="#Page_32">32</a><br /> -Great Lakes route, <a href="#Page_60">60</a><br /> -Grebe, <a href="#Page_34">34</a><br /> -Grosbeak, <a href="#Page_45">45</a>, <a href="#Page_74">74</a><br /> - black-headed, <a href="#Page_37">37</a><br /> - evening, <a href="#Page_74">74</a><br /> - pine, <a href="#Page_72">72</a><br /> - rose-breasted, <a href="#Page_33">33</a>, <a href="#Page_45">45</a>, <a href="#Page_46">46 (map)</a><br /> -Gross, Alfred O., <a href="#Page_74">74</a><br /> -Groups, movements of, <a href="#Page_12">12</a><br /> -Grouse, ruffed, <a href="#Page_82">82</a><br /> -Gull, <a href="#Page_16">16</a>, <a href="#Page_68">68</a>, <a href="#Page_73">73</a>, <a href="#Page_78">78</a><br /> - herring, <a href="#Page_73">73</a><br /> - Ross's, <a href="#Page_68">68</a><br /> -<br /> -<a id="Alph_H"></a>Hawk, <a href="#Page_2">2</a>, <a href="#Page_16">16</a>, <a href="#Page_19">19</a>, <a href="#Page_26">26</a>, <a href="#Page_34">34</a>, <a href="#Page_42">42</a><br /> - broad-winged, <a href="#Page_16">16</a><br /> - Cooper's, <a href="#Page_16">16</a><br /> - duck, <a href="#Page_19">19</a>, <a href="#Page_20">20</a><br /> - red-tailed, <a href="#Page_16">16</a><br /> - rough-legged, <a href="#Page_16">16</a><br /> - sharp-shinned, <a href="#Page_16">16</a><br /> - Swainson's, <a href="#Page_16">16</a><br /> -Herodotus, <a href="#Page_2">2</a><br /> -Heron, <a href="#Page_19">19</a>, <a href="#Page_20">20</a>, <a href="#Page_73">73</a><br /> - black-crowned night, <a href="#Page_73">73</a><br /> - little blue, <a href="#Page_73">73</a><br /> - snowy, <a href="#Page_73">73</a><br /> -Hesiod, <a href="#Page_2">2</a><br /> -Hesperornis, <a href="#Page_11">11</a><br /> -Hibernation, <a href="#Page_4">4</a><br /> -Homer, <a href="#Page_2">2</a><br /> -Homing instinct, <a href="#Page_30">30</a><br /> -Hummingbird, ruby-throated, <a href="#Page_79">79</a><br /> -<br /> -<a id="Alph_I"></a>Ichthyornis, <a href="#Page_11">11</a><br /> -Influence of weather, <a href="#Page_80">80</a><br /> -Insects, <a href="#Page_29">29</a><br /> -<br /> -<a id="Alph_J"></a>Jacksnipe, <a href="#Page_37">37</a><br /> -Jaeger, Edmund C., <a href="#Page_5">5</a><br /> -Jaeger, parasitic, <a href="#Page_68">68</a><br /> -Jay, blue, <a href="#Page_34">34</a>, <a href="#Page_83">83</a><br /> -Junco, <a href="#Page_10">10</a>, <a href="#Page_34">34</a>, <a href="#Page_72">72</a><br /> - slate-colored, <a href="#Page_37">37</a>, <a href="#Page_70">70</a>, <a href="#Page_75">75</a><br /> -<br /> -<a id="Alph_K"></a>Kingbird, <a href="#Page_32">32</a>, <a href="#Page_42">42</a>, <a href="#Page_55">55</a><br /> -Kingfisher, belted, <a href="#Page_34">34</a><br /> -Kinglet, <a href="#Page_77">77</a><br /> - golden-crowned, <a href="#Page_75">75</a><br /> -Kite, <a href="#Page_4">4</a><br /> -Kittiwake, red-legged, <a href="#Page_68">68</a><br /> -Knot, <a href="#Page_11">11</a>, <a href="#Page_42">42</a><br /> -<br /> -<a id="Alph_L"></a>Lapwing, <a href="#Page_28">28</a><br /> -Lark, horned, <a href="#Page_19">19</a><br /> - meadow, <a href="#Page_34">34</a>, <a href="#Page_76">76</a><br /> -Lewis, Harrison F., <a href="#Page_57">57</a><br /> -Lincoln, Frederick C., <a href="#Page_5">5</a><br /> -Long distance migrations, <a href="#Page_38">38</a><br /> -Longspur, <a href="#Page_34">34</a>, <a href="#Page_76">76</a><br /> -Lapland, <a href="#Page_37">37</a>, <a href="#Page_75">75</a><br /> -Loon, <a href="#Page_16">16</a><br /> - yellow-billed, <a href="#Page_84">84</a>, <a href="#Page_85">85</a><br /> -<br /> -<a id="Alph_M"></a>Mackenzie Valley route, <a href="#Page_60">60</a><br /> -Magnetic sense, <a href="#Page_30">30</a><br /> -Magnus, Olaus, <a href="#Page_4">4</a><br /> -Mallard, <a href="#Page_22">22</a>, <a href="#Page_31">31</a>, <a href="#Page_33">33</a>, <a href="#Page_58">58</a><br /> -Man-o'-war bird, <a href="#Page_30">30</a><br /> -Martin, purple, <a href="#Page_12">12</a><br /> -Migration, advantages of, <a href="#Page_6">6</a><br /> - altitudes, <a href="#Page_26">26</a><br /> - distances, <a href="#Page_38">38</a><br /> - diurnal, <a href="#Page_15">15</a><br /> - fall, <a href="#Page_37">37</a><br /> - historical accounts, <a href="#Page_4">4</a><br /> - long distance, <a href="#Page_38">38</a><br /> - mystery of, <a href="#Page_4">4</a><br /> - nocturnal, <a href="#Page_15">15</a><br /> - origin, <a href="#Page_7">7</a><br /> - perils, <a href="#Page_75">75</a><br /> - problems, <a href="#Page_81">81</a><br /> - routes, <a href="#Page_41">41</a><br /> - segregation during, <a href="#Page_31">31</a><br /> - short, <a href="#Page_34">34</a><br /> - species and groups, <a href="#Page_12">12</a><br /> - speed, <a href="#Page_18">18</a><br /> - theories of causes, <a href="#Page_7">7</a><br /> - undetermined, <a href="#Page_34">34</a><br /> - vagrant, <a href="#Page_73">73</a><br /> - variable, <a href="#Page_35">35</a><br /> - vertical, <a href="#Page_72">72</a><br /> - weather, <a href="#Page_80">80</a><br /> -Mississippi Valley route, <a href="#Page_60">60</a><br /> -Mockingbird, <a href="#Page_83">83</a><br /> -Movements of residents, <a href="#Page_82">82</a><br /> -Movements of species and groups, <a href="#Page_12">12</a><br /> -Murre, <a href="#Page_29">29</a><br /> -Mystery of migration, <a href="#Page_4">4</a><br /> -<br /> -<a id="Alph_N"></a>Nighthawk, <a href="#Page_9">9</a>, <a href="#Page_16">16</a>, <a href="#Page_32">32</a>, <a href="#Page_38">38</a>, <a href="#Page_55">55</a>, <a href="#Page_60">60</a>, <a href="#Page_70">70</a><br /> -Nocturnal migration, <a href="#Page_15">15</a><br /> -Northern ancestral home theory, <a href="#Page_8">8</a><br /> -Nutcracker, Clark's, <a href="#Page_73">73</a><br /> -Nuthatch, <a href="#Page_7">7</a><br /> - white-breasted, <a href="#Page_83">83</a><br /> -<br /> -<a id="Alph_O"></a>Orientation, <a href="#Page_28">28</a><br /> -Origin of migration, <a href="#Page_7">7</a><br /> -Oriole, <a href="#Page_15">15</a><br /> - orchard, <a href="#Page_9">9</a><br /> -Ovenbird, <a href="#Page_70">70</a>, <a href="#Page_78">78</a>, <a href="#Page_80">80</a><br /> -Owl, great horned, <a href="#Page_34">34</a><br /> - screech, <a href="#Page_83">83</a><br /> - snowy, <a href="#Page_12">12</a>, <a href="#Page_74">74</a><br /> -<br /> -<a id="Alph_P"></a>Pacific coast route, <a href="#Page_63">63</a> -<span class="pagenum" id="Page_101">-101-</span><br /> -Pacific oceanic route, <a href="#Page_66">66</a><br /> -Passerella iliaca, <a href="#Page_35">35</a><br /> -Pelican, <a href="#Page_4">4</a>, <a href="#Page_16">16</a>, <a href="#Page_26">26</a><br /> -Perils, aerial obstructions, <a href="#Page_76">76</a><br /> - exhaustion, <a href="#Page_78">78</a><br /> - migration, <a href="#Page_75">75</a><br /> - storms, <a href="#Page_75">75</a><br /> -Pewee, western wood, <a href="#Page_72">72</a><br /> -Phalarope, <a href="#Page_33">33</a><br /> - northern, <a href="#Page_27">27</a><br /> -Photoperiodism, theory of, <a href="#Page_9">9</a><br /> -Pigeon, homing, <a href="#Page_30">30</a>, <a href="#Page_31">31</a><br /> -Pintail, <a href="#Page_22">22</a>, <a href="#Page_55">55</a>, <a href="#Page_62">62</a>, <a href="#Page_79">79</a><br /> -Pipit, <a href="#Page_73">73</a><br /> -Pliny, <a href="#Page_4">4</a><br /> -Plover, <a href="#Page_15">15</a><br /> - golden, <a href="#Page_11">11</a>, <a href="#Page_19">19</a>, <a href="#Page_48">48</a>, <a href="#Page_49">49</a>, <a href="#Page_51">51</a>, <a href="#Page_54">54 (map)</a>, <a href="#Page_66">66</a>, <a href="#Page_68">68</a>, <a href="#Page_71">71</a>, <a href="#Page_79">79</a><br /> - upland, <a href="#Page_15">15</a><br /> -Poor-will, <a href="#Page_5">5</a><br /> -Problems, migration, <a href="#Page_81">81</a><br /> - banding studies, <a href="#Page_81">81</a><br /> - migration of the white-throated sparrow, <a href="#Page_84">84</a><br /> - migration of the yellow-billed loon, <a href="#Page_84">84</a><br /> - movements of residents, <a href="#Page_82">82</a><br /> -<br /> -<a id="Alph_Q"></a>Quail, <a href="#Page_2">2</a>, <a href="#Page_34">34</a><br /> - California, <a href="#Page_82">82</a><br /> - migratory, <a href="#Page_2">2</a><br /> -<br /> -<a id="Alph_R"></a>Rail, <a href="#Page_4">4</a>, <a href="#Page_15">15</a><br /> - Carolina, <a href="#Page_79">79</a><br /> -Raven, <a href="#Page_19">19</a><br /> -Redhead, <a href="#Page_58">58</a>, <a href="#Page_62">62</a>, <a href="#Page_85">85</a><br /> -Redpoll, <a href="#Page_12">12</a><br /> -Redstart, <a href="#Page_14">14</a>, <a href="#Page_45">45</a>, <a href="#Page_47">47 (map)</a>, <a href="#Page_70">70</a>, <a href="#Page_78">78</a><br /> -Residents, movements of, <a href="#Page_82">82</a><br /> -Robin, <a href="#Page_9">9</a>, <a href="#Page_22">22</a>, <a href="#Page_24">24</a>, <a href="#Page_33">33</a>, <a href="#Page_34">34</a>, <a href="#Page_35">35</a>, <a href="#Page_61">61</a>, <a href="#Page_70">70</a>, <a href="#Page_76">76</a><br /> -Routes, <a href="#Page_41">41</a>, <a href="#Page_53">53 (map)</a><br /> - Arctic, <a href="#Page_68">68</a><br /> - Atlantic coast, <a href="#Page_53">53</a><br /> - Atlantic oceanic, <a href="#Page_48">48</a><br /> - "bobolink," <a href="#Page_55">55</a>, <a href="#Page_56">56 (map)</a><br /> - evolution of, <a href="#Page_70">70</a><br /> - flyways, <a href="#Page_46">46</a><br /> - Great Lakes, <a href="#Page_60">60</a><br /> - Great Plains, <a href="#Page_62">62</a><br /> - Mackenzie Valley, <a href="#Page_60">60</a><br /> - Mississippi Valley, <a href="#Page_60">60</a><br /> - narrow, <a href="#Page_42">42</a><br /> - Pacific coast, <a href="#Page_63">63</a><br /> - Pacific oceanic, <a href="#Page_66">66</a><br /> - Rocky Mountain, <a href="#Page_62">62</a><br /> - wide, <a href="#Page_42">42</a><br /> -Rowan, William, <a href="#Page_10">10</a><br /> -<br /> -<a id="Alph_S"></a>Salmon, <a href="#Page_29">29</a><br /> -Sanderling, <a href="#Page_11">11</a>, <a href="#Page_27">27</a><br /> -Sandpiper, <a href="#Page_15">15</a>, <a href="#Page_27">27</a><br /> - Bartramian, <a href="#Page_15">15</a><br /> - purple, <a href="#Page_42">42</a><br /> -Sapsucker, Williamson's, <a href="#Page_72">72</a><br /> -Scaup, <a href="#Page_58">58</a><br /> -Scoter, <a href="#Page_63">63</a><br /> - white-winged, <a href="#Page_59">59</a>, <a href="#Page_65">65</a><br /> -Segregation, <a href="#Page_31">31</a><br /> -Shore bird, <a href="#Page_9">9</a>, <a href="#Page_11">11</a>, <a href="#Page_12">12</a>, <a href="#Page_32">32</a>, <a href="#Page_33">33</a>, <a href="#Page_38">38</a>, <a href="#Page_42">42</a>, <a href="#Page_48">48</a>, <a href="#Page_50">50</a>, <a href="#Page_55">55</a>, <a href="#Page_57">57</a>, <a href="#Page_60">60</a>, <a href="#Page_61">61</a><br /> -Short and undetermined migrations, <a href="#Page_34">34</a><br /> -Shrike, <a href="#Page_19">19</a>, <a href="#Page_34">34</a><br /> - loggerhead, <a href="#Page_37">37</a><br /> -Snipe, <a href="#Page_15">15</a><br /> - Wilson's, <a href="#Page_37">37</a><br /> -Snowbird, <a href="#Page_10">10</a><br /> -Sora, <a href="#Page_79">79</a><br /> -Southern ancestral home theory, <a href="#Page_8">8</a><br /> -Sparrow, <a href="#Page_15">15</a>, <a href="#Page_31">31</a>, <a href="#Page_32">32</a>, <a href="#Page_34">34</a>, <a href="#Page_60">60</a>, <a href="#Page_76">76</a>, <a href="#Page_77">77</a><br /> - chipping, <a href="#Page_37">37</a>, <a href="#Page_70">70</a><br /> - field, <a href="#Page_37">37</a><br /> - fox, <a href="#Page_35">35</a>, <a href="#Page_36">36 (map)</a><br /> - Harris's, <a href="#Page_43">43 (map)</a>, <a href="#Page_44">44</a>, <a href="#Page_45">45</a><br /> - Ipswich, <a href="#Page_43">43</a><br /> - song, <a href="#Page_33">33</a>, <a href="#Page_34">34</a><br /> - swamp, <a href="#Page_75">75</a><br /> - tree, <a href="#Page_34">34</a>, <a href="#Page_37">37</a>, <a href="#Page_75">75</a><br /> - vesper, <a href="#Page_37">37</a><br /> - white-throated, <a href="#Page_75">75</a>, <a href="#Page_84">84</a><br /> -Species, movements of, <a href="#Page_12">12</a><br /> -Speed, flight, <a href="#Page_18">18</a><br /> - migration, <a href="#Page_18">18</a><br /> -Starling, <a href="#Page_4">4</a><br /> -Stork, <a href="#Page_2">2</a>, <a href="#Page_4">4</a>, <a href="#Page_6">6</a>, <a href="#Page_27">27</a><br /> -Storms, <a href="#Page_75">75</a><br /> -Swallow, <a href="#Page_2">2</a>, <a href="#Page_4">4</a>, <a href="#Page_6">6</a>, <a href="#Page_9">9</a>, <a href="#Page_17">17</a>, <a href="#Page_18">18</a>, <a href="#Page_26">26</a>, <a href="#Page_32">32</a>, <a href="#Page_34">34</a>, <a href="#Page_57">57</a><br /> - bank, <a href="#Page_55">55</a><br /> - barn, <a href="#Page_20">20</a>, <a href="#Page_38">38</a>, <a href="#Page_60">60</a><br /> - cliff, <a href="#Page_16">16</a>, <a href="#Page_17">17 (map)</a>, <a href="#Page_26">26</a>, <a href="#Page_38">38</a><br /> - hibernating, <a href="#Page_4">4</a><br /> -Swan, <a href="#Page_4">4</a><br /> -Swift, <a href="#Page_4">4</a>, <a href="#Page_16">16</a>, <a href="#Page_19">19</a>, <a href="#Page_20">20</a>, <a href="#Page_34">34</a><br /> - chimney, <a href="#Page_4">4</a>, <a href="#Page_32">32</a><br /> -<br /> -<a id="Alph_T"></a>Tanager, <a href="#Page_55">55</a>, <a href="#Page_66">66</a><br /> - scarlet, <a href="#Page_33">33</a>, <a href="#Page_44">44 (map)</a>, <a href="#Page_45">45</a><br /> - western, <a href="#Page_65">65 (map)</a>, <a href="#Page_66">66</a>, <a href="#Page_67">67 (map)</a><br /> -Teal, blue-winged, <a href="#Page_20">20</a>, <a href="#Page_55">55</a>, <a href="#Page_58">58</a>, <a href="#Page_60">60</a> -<span class="pagenum" id="Page_102">-102-</span><br /> -Tern, arctic, <a href="#Page_11">11</a>, <a href="#Page_38">38</a>, <a href="#Page_39">39 (map)</a>, <a href="#Page_40">40</a>, <a href="#Page_41">41</a>, <a href="#Page_68">68</a><br /> - common, <a href="#Page_40">40</a><br /> - Forster's, <a href="#Page_40">40</a><br /> - noddy, <a href="#Page_30">30</a><br /> - sooty, <a href="#Page_30">30</a><br /> -Theories of migration, <a href="#Page_7">7</a><br /> -Thrush, <a href="#Page_4">4</a>, <a href="#Page_15">15</a>, <a href="#Page_19">19</a>, <a href="#Page_21">21</a>, <a href="#Page_27">27</a>, <a href="#Page_31">31</a>, <a href="#Page_38">38</a>, <a href="#Page_60">60</a>, <a href="#Page_77">77</a><br /> - gray-cheeked, <a href="#Page_21">21</a>, <a href="#Page_23">23 (map)</a>, <a href="#Page_55">55</a><br /> - hermit, <a href="#Page_75">75</a><br /> - wood, <a href="#Page_55">55</a><br /> -Titlark, <a href="#Page_73">73</a><br /> -Titmouse, <a href="#Page_34">34</a><br /> - tufted, <a href="#Page_82">82</a><br /> -Transmutation, <a href="#Page_5">5</a><br /> -Turd us migratorius, <a href="#Page_35">35</a><br /> -Turnstone, <a href="#Page_11">11</a><br /> -Turtle [dove], <a href="#Page_2">2</a>, <a href="#Page_6">6</a><br /> -<br /> -<a id="Alph_V"></a>Vagrant migration, <a href="#Page_73">73</a><br /> -Variable migrations within species, <a href="#Page_35">35</a><br /> -Vertical migration, <a href="#Page_72">72</a><br /> -Vireo, <a href="#Page_15">15</a>, <a href="#Page_55">55</a>, <a href="#Page_75">75</a>, <a href="#Page_77">77</a><br /> - red-eyed, <a href="#Page_69">69 (map)</a>, <a href="#Page_70">70</a><br /> -Vulture, <a href="#Page_26">26</a><br /> - turkey, <a href="#Page_34">34</a><br /> -<br /> -<a id="Alph_W"></a>Warbler, <a href="#Page_15">15</a>, <a href="#Page_17">17</a>, <a href="#Page_18">18</a>, <a href="#Page_27">27</a>, <a href="#Page_60">60</a>, <a href="#Page_75">75</a>, <a href="#Page_76">76</a><br /> - black and white, <a href="#Page_12">12</a>, <a href="#Page_13">13 (map)</a>, <a href="#Page_14">14 (map)</a><br /> - blackpolled, <a href="#Page_16">16</a>, <a href="#Page_18">18</a>, <a href="#Page_24">24</a>, <a href="#Page_25">25 (map)</a>, <a href="#Page_55">55</a>, <a href="#Page_60">60</a>, <a href="#Page_70">70</a><br /> - black-throated blue, <a href="#Page_14">14</a><br /> - Cape May, <a href="#Page_37">37</a><br /> - golden-winged, <a href="#Page_63">63</a><br /> - Kentucky, <a href="#Page_63">63</a><br /> - myrtle, <a href="#Page_61">61</a>, <a href="#Page_70">70</a><br /> - palm, <a href="#Page_37">37</a><br /> - pine, <a href="#Page_37">37</a><br /> - summer, <a href="#Page_21">21</a><br /> - wood, <a href="#Page_31">31</a>, <a href="#Page_32">32</a><br /> - worm-eating, <a href="#Page_63">63</a><br /> - yellow, <a href="#Page_14">14</a>, <a href="#Page_21">21</a>, <a href="#Page_70">70</a><br /> -Waterfowl, <a href="#Page_20">20</a>, <a href="#Page_47">47</a>, <a href="#Page_55">55</a>, <a href="#Page_58">58</a>, <a href="#Page_59">59</a>, <a href="#Page_61">61</a>, <a href="#Page_64">64</a>,93<br /> -Waxwing, <a href="#Page_32">32</a>, <a href="#Page_33">33</a><br /> - Bohemian, <a href="#Page_12">12</a>, <a href="#Page_74">74</a><br /> -Weather, influence of, <a href="#Page_80">80</a><br /> -Wheatear, Greenland, <a href="#Page_11">11</a><br /> -Widgeon, <a href="#Page_55">55</a><br /> - American, <a href="#Page_62">62</a><br /> -Woodcock, <a href="#Page_37">37</a><br /> -Woodpecker, <a href="#Page_34">34</a><br /> -Wren, <a href="#Page_15">15</a><br /> - Carolina, <a href="#Page_34">34</a>, <a href="#Page_82">82</a>, <a href="#Page_83">83</a><br /> - long-billed marsh, <a href="#Page_33">33</a><br /> - rock, <a href="#Page_37">37</a><br /> - winter, <a href="#Page_34">34</a>, <a href="#Page_75">75</a><br /> -Wrentit, <a href="#Page_82">82</a><br /> -<br /> -<a id="Alph_Y"></a>Yeagley, Henry L., <a href="#Page_30">30</a><br /> -Yellowlegs, lesser, <a href="#Page_21">21</a><br /> -Yellowthroat, Maryland, <a href="#Page_35">35</a>, <a href="#Page_78">78</a><br /> -</p> - -<p class="tdc larger">◯</p> - -<hr class="tb" /> - -<div class="transnote"> -<p class="caption3nb">Transcriber Note</p> - -<p>Illustrations moved to prevent splitting paragraphs. Minor typos corrected.</p> -</div> - -<div style='display:block; margin-top:4em'>*** END OF THE PROJECT GUTENBERG EBOOK USFWS CIRCULAR 16: MIGRATION OF BIRDS (1950) ***</div> -<div style='text-align:left'> - -<div style='display:block; margin:1em 0'> -Updated editions will replace the previous one—the old editions will -be renamed. -</div> - -<div style='display:block; margin:1em 0'> -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. Special rules, set forth in the General Terms of Use part -of this license, apply to copying and distributing Project -Gutenberg™ electronic works to protect the PROJECT GUTENBERG™ -concept and trademark. 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