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diff --git a/old/52382-8.txt b/old/52382-8.txt deleted file mode 100644 index 341a9fd..0000000 --- a/old/52382-8.txt +++ /dev/null @@ -1,2481 +0,0 @@ -The Project Gutenberg EBook of Studies of Birds Killed in Nocturnal -Migration, by Harrison B. Tordoff and Robert M. Mengel - -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'll have -to check the laws of the country where you are located before using this ebook. - - - -Title: Studies of Birds Killed in Nocturnal Migration - -Author: Harrison B. Tordoff - Robert M. Mengel - -Release Date: June 20, 2016 [EBook #52382] - -Language: English - -Character set encoding: ISO-8859-1 - -*** START OF THIS PROJECT GUTENBERG EBOOK STUDIES OF BIRDS *** - - - - -Produced by Judith Wirawan, Chris Curnow, Joseph Cooper -and the Online Distributed Proofreading Team at -http://www.pgdp.net - - - - - - - - - - - UNIVERSITY OF KANSAS PUBLICATIONS - MUSEUM OF NATURAL HISTORY - - - Volume 10, No. 1, pp. 1-44, 6 figures in text, 2 tables - - September 12, 1956 - - - Studies of Birds - Killed in Nocturnal Migration - - - BY - HARRISON B. TORDOFF AND ROBERT M. MENGEL - - - UNIVERSITY OF KANSAS - LAWRENCE - 1956 - - * * * * * - - UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY - - Editors: E. Raymond Hall, Chairman, A. Byron Leonard, - Robert W. Wilson - - - Volume 10, No. 1, pp. 1-44, 6 figures in text, 2 tables - Published September 12, 1956 - - - UNIVERSITY OF KANSAS - Lawrence, Kansas - - - PRINTED BY - FERD VOILAND, JR., STATE PRINTER - TOPEKA, KANSAS - 1956 - - [Illustration: Logo] - - 26-3856 - - - * * * * * - -Studies of Birds Killed in Nocturnal Migration - -BY HARRISON B. TORDOFF AND ROBERT M. MENGEL - - - - -Contents - - - PAGE - - Introduction 4 - - Accidents to Migrating Birds in early October, 1954 6 - General 6 - Accidents at Topeka, Kansas 6 - Description of WIBW-TV tower 7 - Weather conditions 7 - - Acknowledgments 7 - - Notes on the Species Killed at Topeka 8 - - Randomness of the Sample 17 - - Number of Migrants 18 - - Differential Migration of Sex- and Age-classes 20 - History of the subject 20 - Differential migration of sex- and age-classes as - shown by the Topeka sample 23 - - Molt in Relation to Migration 29 - General comment 29 - Molt in the Topeka sample 30 - - Size Differences according to Sex and Age 31 - Linear measurements 31 - Weights 32 - - Computations of Longevity and Survival 38 - - Processing of Samples 38 - - Summary 39 - - Literature Cited 41 - - - - - -Introduction - - -This paper is primarily an analysis of a sample of migrant birds -killed in the autumn of 1954 by striking a television tower one mile -west of Topeka, Shawnee County, Kansas. Secondarily, some aspects of -migration involved in studies of this kind are discussed and -historical background is presented. - -Considerable interest has been occasioned in recent years in the -eastern United States by large-scale accidents to night-migrating -birds. Most accidents have occurred in the autumn. The widespread -adoption by airports of an instrument called the ceilometer, which -measures the height of cloud ceilings by reflecting from them a -high-powered beam of light, has proved under certain conditions to be -catastrophic to night-flying birds. Among the recent reports of such -accidents are those of Spofford (1949) and Laskey (1951) for -Nashville, Tennessee, Howell and Tanner (1951) for Knoxville, -Tennessee, and Lovell (1952) for Louisville, Kentucky. Recently -Howell, Laskey, and Tanner (1954) reviewed ceilometer "tragedies" -without being able to determine the exact reason for their lethal -effectiveness. Less publicized so far have been mass collisions of -birds with another class of obstacles, tall radio and television -towers. These slender towers, usually 500 to 1000 feet tall, are -increasing rapidly in numbers and there is reason to suppose that they -will take a correspondingly larger toll of bird life. - -Notice has long been given by ornithologists to mass destruction of -birds by more conventional solid obstructions to passage, and -newspapers occasionally mention birds killed at such well-known points -as the Washington Monument and the Empire State Building. - -Seventy-five years ago, J. A. Allen (1880) published the results of -questionnaires circulated by William Brewster to lighthouse keepers. -Brewster himself (1886) described destruction of birds at a lighthouse -in the Bay of Fundy, paying keen attention to behavior of the birds -and the exact conditions under which nocturnal flight and accidents -occurred. The subject also received attention in several countries -across the Atlantic. Destruction of birds at Irish lighthouses was -carefully noted over a period of years and the results were published -periodically, culminating in R. M. Barrington's massive report (1900) -which remains in some ways the most thorough of its type. - -While conservation-minded individuals have been concerned with the -tremendous mortality involved in these various events, the ill wind -blows some good in that, properly used, the data provided by such -accidents can shed light on many obscure aspects of bird migration. -Each accidental kill of birds affords a cross-section, approaching in -variable degree a random sample, of the migrants passing a given point -on a given date. The types of information provided by such kills are -numerous, for example: (1) information on the presence of various -species and the dates of their occurrence; (2) information on the -relative abundance of species; (3) quantitative data on the relative -sizes of males and females, and immatures and adults (of importance to -taxonomic ornithology); (4) information on the relative times of -migration of males, females, adults, and young; (5) information on -molts and plumages; (6) quantitative information on composition by -subspecies of migrants of the same species; (7) physiological data -(fat condition, _etc._) pertinent to the study of migration; and -probably others. - -In spite of the great potential of this kind of material, the majority -of ornithologists with access to such data have contented themselves -with listing the species and sometimes the numbers of birds killed. A -few have gone further. James T. Tanner (unpublished) attempted to -compute the longevity of the Ovenbird (_Seiurus aurocapillus_) by -analysis of ceilometer-killed birds at Knoxville, Tennessee (see -below). Mention should be made of the reports of Rintoul and Baxter -(1914) supplemented by Ticehurst (1916) who used rather small numbers -of birds killed at Scottish lighthouses in studies of molt. However, -the only effort to utilize the results of accidental kills on a large -scale over a period of years appears to have been that, already -mentioned, of Barrington (1900) and his co-workers in Ireland. An idea -of the potentialities of the large recent kills in the United States -may be obtained when it is recalled that in the 18 years of -Barrington's work, which embodied some 1000 reports from lighthouse -keepers, Barrington obtained for study only about 2000 specimens, many -of these consisting of wings and feet only (Barrington's paper not -seen in original; see J. A. Allen, 1901:205). More recently Dobben and -Bruyns (1939) have analyzed the age and sex classes of some birds -killed at lighthouses in Holland. - -As far as we have learned, there is no previous thorough analysis in -the literature of large, accidentally-killed samples of birds. On the -following pages we emphasize some of the uses which can be made of -such material. We think that intensive analyses of such events, -whenever they occur, should become a regular part of ornithological -investigation and that integration of numerous studies of such -incidents will provide an unprecedented mass of information on -migration. - - - - -Accidents to Migrating Birds in early October, 1954 - - -GENERAL.--The few days around the end of the first week of October, -1954, were notable for a series of accidents which occurred to -migrating birds over much of eastern United States. So far as we know, -these were all associated with an extensive belt of bad weather (cold -fronts and stationary fronts) which covered much of the country during -that period, and the accidents involved ceilometers and solid -structures alike. Accidents known to us occurred as far south as -Macon, Georgia (David W. Johnston, letter: Nov. 1, 1954), as far north -as New York City, where many migrants were killed at the Empire State -Building (_New York Times_, Thursday, October 7, 1954, p. 1) and -elsewhere, and as far west as Smoky Hill Air Force Base at Salina, -Kansas (ceilometer, October 7, some birds received at the University -of Kansas). Some of the above, and incidents from a number of other -localities, were mentioned in varying detail in _Audubon Field Notes_ -(vol. 9, no. 1, pp. 6, 10, 15, 17, 18, 32, February, 1955). Still -other accidents occurred at Columbia, Missouri (Richard P. -Grossenheider, verbal communication), and Topeka, Kansas (present -paper). Some probably have escaped our notice; summaries of some of -these will probably appear in ornithological journals for some time to -come. At Robins Air Force Base near Macon, Georgia, at least 50,000 -birds were killed, of which about 2500, representing 54 species, were -picked up (Johnston, _loc. cit._). - - -ACCIDENTS AT TOPEKA, KANSAS.--At Topeka, Shawnee County, Kansas, all -birds were killed by collision with the newly-erected (1954) -television transmitting tower of station WIBW-TV. This tower is one -mile west of the city. - -The first casualties (see Table 1 for all others) were a Sora -(_Porzana carolina_) and a Yellow-bellied Flycatcher (_Empidonax -flaviventris_) found on September 7. The major accidents, however, -occurred on the nights of September 24-25, September 30-October 1, -October 5-6, and October 6-7. Totals of birds picked up (probably over -95 per cent of birds killed) are given in Table 1, in which each date -given is that of the day after the kill, _i. e._, the date on which -the birds were collected. - -All major kills occurred on cloudy and foggy nights associated with -frontal weather. Throughout the period a few birds struck the tower -even on fairly clear nights, and minor but appreciable "falls" -occurred on the nights of October 4-5, 7-8, and 22-23. A few birds -killed probably were overlooked for a time and found their way into -later samples. This is especially probable in the case of some birds -entered under date of October 23, as many of these were somewhat -desiccated. Weights clearly altered by desiccation or mutilation were -not recorded. Reports of these accidents have been published by Carson -(1954 a, b, and c). - -According to Carson (1954c:27), the majority of birds killed on nights -of heavy flight fell "between three and four o'clock in the morning -when skies were overcast and a cool front moved in from the north. Due -to the cooperation of the watchmen it is thought that most of the -birds that were killed were recovered. Of course some injured birds in -hiding were not found and some were lost to predators." - - -DESCRIPTION OF WIBW-TV TOWER.--The tower is 950 feet tall and stands -on a hill approximately 1000 feet above sea level. The fact that the -tower is on a hill places the top of the tower at 1010 feet above the -elevation of the average local terrain. The tower is triangular in -cross-section, each face seven feet wide, and is constructed of -six-inch steel L-beams with three-inch cross-members every seven feet -and smaller diagonal cross-members. It has no taper and bears a -transmitting antenna on the top. The tower is supported by 12 guy -wires, 3 wires attaching at each of 4 levels. The cables extend south, -WNW, and NNE from the tower and are 1-1/2 inches in diameter. The -tower is lighted by a series of red lights, some flashing and others -steady. The transmitter was not in operation when the accidents took -place. - - -WEATHER CONDITIONS.--All major kills at Topeka occurred when migrating -birds encountered either a cold front or a stationary front lying over -eastern Kansas. Typically, this frontal weather included rain, fog, -and cloud ceilings down to as low as 800 to 1000 feet. Weather of this -type presumably forces the migrating birds to fly below the cloud -ceiling and thus brings them within the altitudinal range of the -television towers. - - - - -Acknowledgments - - -We gratefully acknowledge our debt to the Topeka Audubon Society for -making this study possible by carefully collecting birds killed at the -television tower. L. B. Carson deserves special mention for his -general supervision of the bird collecting by the members of the -Topeka Audubon Society. Members of the Society and others who picked -up birds under the television tower were: Mrs. Lloyd Biggs, Elaine -Carson, L. B. Carson, Jesse A. Eddy, Elizabeth Fisher, Mrs. Walter -Huxman, Florence McKinney, Mrs. Charles Martin, Mrs. Fred P. Martin, -T. W. Nelson, Fred Prebble, Grace Prebble, Orville Rice, Mrs. G. -Warren Scholl, E. W. Senne, and Beatrice Swenson. - -We received equally important assistance from students and staff of -the University of Kansas in recording of data and preparation of -specimens. The following helped in these ways: Rollin H. Baker, R. W. -Dickerman, David L. Hardy, J. W. Hardy, Jane S. Mengel, Larry D. -Mosby, Richard Van Gelder, South G. Van Hoose, and Glen E. Woolfenden. -We are indebted to the Interlibrary Loan Service of the University of -Kansas Library for help in securing certain reference works. Robert -Sokal of the University of Kansas gave helpful advice concerning -statistical procedures. - - - - -Notes on the Species Killed at Topeka - - -A list of numbers and kinds of birds killed is given in Table 1. -Discussion of data afforded by certain species for which, large -samples were available will be found below. There are additionally -certain data afforded by the sample and certain comments to be made on -various species which can be handled most conveniently in an annotated -list. In this list we have included all weight data (still scarce for -many North American birds), comments on status in Kansas of various -species, results of comparisons to determine subspecies, and -miscellaneous observations. Weights of birds are given in grams and -were taken on a triple-beam balance. Fat condition is given in the -scale proposed by McCabe (1943:556). Weight data from birds migrating -at night should be especially useful because these migrants all have -relatively empty crops and stomachs, thus reducing variability. Not -all birds were suitable for weighing and measuring, for a variety of -reasons. This accounts for discrepancies in totals between Table 1 and -the annotated list. - -All passerine species were aged by noting the degree of ossification -of the skull. In no case, of the more than a thousand passerines aged -by examination of the skull, did we find difficulty in determining -whether an individual was a bird of the year or an adult. We found no -specimens in which ossification of the skull was nearing completion. -In the several species in our sample with distinctive first-winter -plumages, we found complete agreement in age as shown by plumage and -by condition of the skull. We think this is further proof, if such is -needed, that this method of aging is thoroughly reliable in early -autumn for the passerine species included in our sample and for others -with similar breeding seasons. - -TABLE 1.--BIRDS KILLED AT A TELEVISION TOWER AT TOPEKA, KANSAS, IN -1954 - -See annotated list for division into sex- and age-classes. Where -discrepancies exist between totals given here and totals given in the -annotated list, these result from the fact that some specimens could -not be sexed and aged. - - A: Sept. 25 - B: Oct. 1 - C: Oct. 3 - D: Oct. 4 - E: Oct. 5 - F: Oct. 6 - G: Oct. 7 - H: Oct. 8 - I: Oct. 9 - J: Oct. 10 - K: Oct. 23 - L: Totals - - =======================+===+===+===+===+===+===+===+===+===+===+===+==== - | A | B | C | D | E | F | G | H | I | J | K | L - -----------------------+---+---+---+---+---+---+---+---+---+---+---+---- - Pied-billed Grebe | | 1| | | | 1| | | 1| | | 3 - Green Heron | | | | | | 1| | | | | | 1 - Blue-winged Teal | | 1| | | | 1| 6| | | | | 8 - Virginia Rail | | 3| | | | 1| | | | | | 4 - Sora | 1| 6| | | | 1| 1| 1| | | | 10 - American Coot | | | | | | 3| | | | | | 3 - Mourning Dove | | 8| | | 1| | | | | | 1| 10 - Yellow-billed Cuckoo | | | | | | 1| | | | | | 1 - Black-billed Cuckoo | | | | | | | 1| | | | | 1 - Yellow-shafted Flicker | 3| | | | | | | | | | | 3 - Yellow-bellied | | | | | | | | | | | | - Flycatcher | | | | | | | 1| | | | | 1 - House Wren | 2| 3| | | | 1| 2| 1| | | 1| 10 - Long-billed Marsh Wren | | 1| | | | 1| 1| | | | | 3 - Short-billed Marsh Wren| 1| 2| | | | | 1| | | | | 4 - Catbird | 1| 28| 1| | 1| 6| 6| | | | | 43 - Brown Thrasher | | 1| | | | 1| | 1| | | | 3 - Wood Thrush | | 3| | | | | | | | | | 3 - Hermit Thrush | | | | | | | | | | 1| | 1 - Olive-backed Thrush | | 14| | 1| | | 1| | | | | 16 - Golden-crowned Kinglet | | | | | | | | | | 1| 5| 6 - Ruby-crowned Kinglet | 2| 1| | | | | 8| 1| 1| | 1| 14 - Yellow-throated Vireo | | 1| | | | | | | | | | 1 - Blue-headed Vireo | 1| 19| | 1| 2| 5| 8| 3| 1| | | 40 - Red-eyed Vireo | 18| 36| | | 2| 13| 2| 3| | | 1| 75 - Philadelphia Vireo | 3| 9| | | | | | | | | | 12 - Warbling Vireo | 8| 19| 1| | 4| 1| 1| | | | | 34 - Black and White Warbler| 1| 1| | | | 3| | | | | | 5 - Tennessee Warbler | | 1| | | 1| 2| 1| | | | | 5 - Orange-crowned Warbler | 7| 14| | | 1| 4| 19| 5| 1| 1| | 52 - Nashville Warbler | 7| 94| 4| | 3| 39| 27| 5| | 1| 1| 181 - Parula Warbler | | | | | | | 1| | 1| | | 2 - Yellow Warbler | 3| 3| | | | 1| 1| | | | | 8 - Magnolia Warbler | | 1| | | | 2| | | | | | 3 - Black-throated Blue | | | | | | | | | | | | - Warbler | | | | | | | 2| | | | 1| 3 - Myrtle Warbler | | | | | | | | | 1| | | 1 - Black-throated Green | | | | | | | | | | | | - Warbler | | | | | | | | | | 1| | 1 - Chestnut-sided Warbler | | 1| | | | | | | 1| | | 2 - Bay-breasted Warbler | 1| | | | | 2| | | | | | 3 - Palm Warbler | 3| | | | | | | | | | 1| 4 - Oven-bird | 4| 21| | | | 2| 3| 1| | | 1| 32 - Northern Water-thrush | | 5| | | | | | | | 1| | 6 - Mourning Warbler | 15| 64| | | 2| 11| 2| 1| | | | 95 - Yellow-throat | 10|115| 2| | 4| 25| 18| 1| 1| | | 176 - Yellow-breasted Chat | | 1| | | | | | | | | | 1 - Wilson Warbler | 1| 2| | | | | | | | | | 3 - Canada Warbler | | 2| | | | | | | | | | 2 - American Redstart | 1| | | | | | | | | | | 1 - Bobolink | | 4| | | | | | | | | | 4 - Rose-breasted Grosbeak | | 2| | | | | | | | | | 2 - Indigo Bunting | | 1| | | 2| 3| 1| | | | | 7 - Dickcissel | | 31| | | 1| 3| 1| | | | | 36 - Savannah Sparrow | 1| 6| | 1| | 1| 5| 1| | | 1| 16 - Grasshopper Sparrow | | 7| | | 2| 3| 3| 1| 1| | 1| 18 - Leconte Sparrow | | | | | | | | | | | 3| 3 - Sharp-tailed Sparrow | | | | | | 1| 1| | | 1| | 3 - Slate-colored Junco | | | | | | | | | | | 1| 1 - Clay-colored Sparrow | | 11| 1| | | 2| | 1| | | | 15 - Fox Sparrow | | | | | | | | | | | 1| 1 - Lincoln Sparrow | 41| 7| | | 5| 22| 3| 1| | | 3| 82 - Swamp Sparrow | | 1| | | | 1| 2| | | | | 4 - Song Sparrow | | | | | | | | | | | 2| 2 - Total--species | 22| 41| 6| 3| 13| 31| 29| 16| 10| 8| 15| 61 - Total--individuals | 94|585| 16| 3| 26|146|147| 31| 10| 8| 24|1090 - ------------------------------------------------------------------------ - -The annotated list may be consulted for further data in connection -with the species listed in Table 1. As is indicated below, we regard -the figures of this sample as unreliable to an unknown degree in -comparing the relative abundance of one species with another. -Accumulation of such data from various localities, however, should -prove useful in another type of comparison. Samples of the same -species killed in the same way at about the same time at different -localities should be directly comparable. Eventually, this should -provide us with a means of determining relative abundance of a species -in different parts of its migratory route. - -Approximately 200 of the most interesting specimens were preserved as -study skins and are in the University of Kansas Museum of Natural -History. An effort was made to preserve at least one of each species, -and we fell only a few short of this goal. All of the forms rare in -Kansas are represented by skins. We could see no reason to list the -preserved specimens in detail here. Species of which no study skins -were made, however, are so marked. - -So far as we can tell, no truly western subspecies (from west of the -Great Plains) occurred in the Topeka sample. Probably most or all of -the birds came from areas more or less directly north of eastern -Kansas. - -In critical areas where different subspecies of the same species occur -together in migration, data from samples of this kind should prove -enlightening. In future analyses, conducted in such areas, it might be -possible to preserve all specimens of some of the variable species, or -at least to measure all individuals of species in which size is the -most important variable character. Quantitative study could then be -made of the different geographic variants occurring, their proportions -in the migrant population determined, and their origins deduced. In -studying populations of Painted Buntings (_Passerina ciris_) wintering -in Mexico, Storer (1951) has provided an interesting demonstration of -methods which can be applied to such samples. - -A few bats killed at the tower provided a surprise. They will be -discussed separately by Richard Van Gelder. - - _Podilymbus p. podiceps._ Pied-billed Grebe.--Weights: male, - 394.8 (all weights in grams); females, 332.5, 289.7; all - fat. - - _Butorides v. virescens._ Green Heron.--Weight: 1 (unsexed), - 168.6. - - _Anas discors._ Blue-winged Teal.--Weights: 4 males, mean - 421.2 (391.3-458.1); 3 females, 367.7, 371.6, 393.2; all - fat. - - _Rallus limicola._ Virginia Rail.--Weights: 3 males, 73.7, - 83.2, 90.5; 1 female, 67.3; moderately fat to fat. - - _Porzana carolina._ Sora.--Weights: 4 males, mean 76.8 - (68.7-89.9); 3 females, 62.6, 63.2, 63.5; moderately fat to - very fat. - - _Fulica americana._ American Coot.--Weights: 2 females, - 385.3, 530.0, both fat. None preserved. - - _Zenaidura macroura marginella._ Mourning Dove.--Weights: 2 - adult males, 121.8, 140.2; 3 immature males, 113.1, 126.1, - 130.0; 3 adult females, 122.5, 126.9, 136.0; 2 immature - females, 129.4, 132.7; moderately fat to very fat. The - presence of Mourning Doves in the sample is interesting as - these birds are not generally regarded as night migrants. - Conceivably the specimens were local birds going to roost. - None preserved. - - _Colaptes auratus luteus._ Yellow-shafted Flicker.--Weights: - 2 males, 126.0, 139.4, little fat. Flickers have several - times been recorded as night migrants. - - _Empidonax flaviventris._ Yellow-bellied - Flycatcher.--Weight: 1 immature male, 11.9, moderately fat. - This is a rare species in Kansas, the present being the - ninth preserved specimen for the State. - - _Troglodytes aëdon parkmanii._ House Wren.--Weights: 4 adult - males, mean 10.5 (9.8-10.9), 2 immature males, 9.0, 11.3; 1 - adult female, 9.9, 1 immature female, 7.0; no fat (im. - [**Female symbol]) to fat. - - _Telmatodytes palustris dissaëptus._ Long-billed Marsh - Wren.--Weights: 1 adult male, 10.8; 1 adult female, 9.2; - both moderately fat. The specimens are moderately bright and - rufescent above, being typical of the populations of the - central plains. - - _Cistothorus platensis stellaris._ Short-billed Marsh - Wren.--Weights: 1 immature male, 8.2; 1 adult female, 8.1; - immature female, 8.2; all fat. - - _Dumetella carolinensis._ Catbird.--Weights: 6 adult males, - mean 37.5 (34.1-42.5), little fat to very fat; 14 immature - males, mean 37.57 ± .94 (standard error), S. D. (standard - deviation) 3.37, little fat to fat; 11 adult females, mean - 39.09 ± .94, S. D. 2.97, little fat to fat; 12 immature - females, mean 38.42 ± .83, S. D. 2.74, moderately fat to - fat. - - _Toxostoma r. rufum._ Brown Thrasher.--Weight: 1 immature - male, 60.2, little fat. - - _Hylocichla mustelina._ Wood Thrush.--Weights: 1 adult male, - 54.2, moderately fat; 2 adult females, 44.6, 45.7, little - fat and fat, respectively. - - _Hylocichla ustulata swainsonii._ Olive-backed - Thrush.--Weights: 6 immature males, mean 31.0 (28.1-33.2), - little fat to fat; 6 adult females, mean 29.6 (27.1-35.0), - moderately fat to fat; 3 immature females, 27.1, 33.8, 35.8, - little fat to fat. The absence of adult males in our sample - of 15 birds is noteworthy but inexplicable with our few - data. - - _Regulus s. satrapa._ Golden-crowned Kinglet.--Weights: 1 - adult male, 6.7, moderately fat; 2 immature males, 6.5, 7.4, - moderately fat and fat; 2 adult females, 7.3, 7.4, - moderately fat and fat; 1 immature female, 7.2, moderately - fat. - - _Regulus c. calendula._ Ruby-crowned Kinglet.--Weights: 3 - adult males, 6.2, 7.6, 8.2, little fat to fat; 1 immature - male, 6.6, fat; 4 adult females, mean 6.1 (5.6-6.7), - moderately fat to fat; 3 immature females, 5.8, 6.6, 7.0, - moderately fat to fat. - - _Vireo flavifrons._ Yellow-throated Vireo.--Weight: 1 - immature male, 21.5, very fat. - - _Vireo s. solitarius._ Blue-headed Vireo.--Weights: 9 adult - males, mean 17.7 (16.6-19.5), little fat to very fat; 17 - immature males, mean 17.53 ± .46, S. D. 1.83, no fat (13.8) - to very fat (21.3); 7 adult females, mean 17.6 (15.0-21.6), - moderately fat to very fat; 6 immature females, mean 17.0 - (14.5-18.9), moderately fat to fat. Surprisingly numerous in - the sample. - - _Vireo olivaceus._ Red-eyed Vireo.--Weights: 1 adult male, - 16.1, moderately fat; 38 immature males, mean 21.21 ± .43, - S. D. 2.60, little fat (1 specimen) to excessively fat, - mostly moderately fat or fat; 2 adult females, 18.1, 18.1, - both fat; 23 immature females, mean 19.28 ± .46, S. D. 2.16, - little (2 specimens) to very fat, mostly fat. - - Wing length: 1 adult male, 79.1; 38 immature males, mean - 78.05 ± .30, S. D. 1.80; 2 adult females, 76.3, 79.0, 23 - immature females, mean 75.83 ± .42, S. D. 1.99. - - As mentioned below, the presence of only 3 adults in the - sample of 64 Red-eyed Vireos is highly significant and their - occurrence only in the earlier samples is strong evidence of - early migration by the adults. - - _Vireo philadelphicus._ Philadelphia Vireo.--Weights: 2 - adult males, 12.1, 15.9, moderately fat and very fat; 2 - immature males, 11.1, 13.2, fat and very fat; 2 adult - females, 13.1, 14.2, both fat; 5 immature females, mean 14.1 - (12.0-15.2), moderately fat to very fat. - - This species previously has been collected in Kansas only - twice. Both records are from Doniphan County in September, - 1922. Field observers occasionally record the Philadelphia - Vireo in eastern Kansas. Long (1940:450) calls it a "very - rare migrant in the extreme east." Our sample of 12 birds - killed on two nights (and probably after the peak of - migration of this species) leads us to think that this vireo - is actually a regular, but overlooked, migrant in fair - numbers. - - _Vireo g. gilvus._ Warbling Vireo.--Weights: 12 adult males, - mean 15.92 ± .43, S. D. 1.44, moderately fat to very fat; 8 - immature males, mean 16.64 (14.2-17.8), fat to very fat; 5 - adult females, mean 16.1 (13.7-18.0), fat to very fat; 5 - immature females, mean 15.4 (14.1-17.8), little fat to fat. - - Wing length: 12 adult males, mean 73.08 ± .49, S. D. 1.64; 8 - immature males, mean 71.15 (69.9-72.8); 5 adult females, - mean 70.0 (69.2-71.0); 5 immature females, mean 68.4 - (67.7-70.3). - - Tail length: 12 adult males, mean 53.33 ± .53, S. D. 1.77; 8 - immature males, mean 50.03 (47.1-51.3); 4 adult females, - mean 48.6 (47.7-49.8); 5 immature females, mean 49.2 - (47.3-53.0). - - There is no indication that western birds (_V. g. - swainsonii_) make up any part of this sample. - - The sample of 34 Warbling Vireos is too small to show the - significance, if any, of the 2:1 ratio of males to females - in the sample. Adequate samples of this species, taken at - intervals, would add interesting information on time of - migration of the four sex- and age-classes. - - _Mniotilta varia._ Black and White Warbler.--Weights: 1 - adult male, 12.5, fat; 2 adult females, 10.0, 10.0, little - fat, fat. - - _Vermivora peregrina._ Tennessee Warbler.--Weights: 1 adult - male, 10.9, very fat; 1 immature male, 12.9, very fat; 2 - adult females, 9.1, 12.5, moderately fat and very fat. The - relative scarcity of Tennessee Warblers in the sample is - surprising. They are common in the area in spring. - - _Vermivora c. celata._ Orange-crowned Warbler.--Weights: 9 - adult males, mean 8.8 (7.7-10.9), little fat to fat; 13 - immature males, mean 8.92 ± .15, S. D. .53, little fat to - fat; 5 adult females, mean 8.8 (8.3-10.3), little fat to - moderately fat; 17 immature females, mean 9.13 ± .08, S. D. - .72, little fat to fat. Of the 19 Orange-crowned Warblers - killed on October 7, 11 had little fat, 6 were moderately - fat, and only 2 were fat. No one-night sample of any other - warbler killed at Topeka had less fat than this group of - warblers. Furthermore, our sample (including 11 males) from - October 7 (all sex- and age-classes) averaged 8.81 grams; - the sample of 13 (including only 4 males) from October 1 - averaged 9.1 grams. If one can assume, for any one species, - that individuals undertake nocturnal migration only when - they are physiologically ready, and this includes a certain - amount of fat as a fuel source (Wolfson, 1954), then this - further assumption seems justified: birds killed in - migration with little fat must have flown longer or farther - or both than birds killed with more fat. No further - speculation on this point is permissible with our data, but - the possibilities for study of future large kills, - especially where actual time of death of the birds is known, - are obvious. - - _Vermivora r. ruficapilla._ Nashville Warbler.--More - Nashville Warblers were picked up at Topeka than any other - species and they are discussed in detail elsewhere in this - report. The four sex- and age-classes can be identified with - fair accuracy on plumage characteristics alone. Adult males - have a large amount of reddish-brown in the crown, not - completely veiled by the gray tips of the crown feathers. - Immature males have a smaller but distinct crown patch, - usually completely veiled. All males, compared with females, - are grayer on the sides of the head, have a more nearly - white eye-ring, and show clearer yellow on the throat. Adult - females differ from immature females in that they more often - have a trace of rufous in the crown and tend to be brighter - below than the immatures. Of 177 specimens, 20 were very - fat, 108 were fat, 46 were moderately fat, and 3 had little - fat. - - _Parula americana._ Parula Warbler.--Weight: 1 adult female, - 7.9, fat. - - _Dendroica petechia aestiva._ Yellow Warbler.--Weights: 1 - immature male, 10.2, fat; 3 adult females, 8.8, 9.5, 10.1, - moderately fat; 2 immature females, 9.0, 9.4, little fat and - fat. - - _Dendroica magnolia._ Magnolia Warbler.--Weights: 1 adult - female, 9.0, moderately fat; 2 immature females, 7.9, 10.3, - moderately fat and fat. - - _Dendroica c. caerulescens._ Black-throated Blue - Warbler.--Weights: 2 immature males, 13.8, 14.1, excessively - fat; 1 immature female, 11.4, fat. This species is rare in - Kansas. Although its breeding range is almost entirely east - and north of Kansas, records in files at the University of - Kansas show that more specimens have been taken in western - than in eastern Kansas. - - _Dendroica c. coronata._ Myrtle Warbler.--Weight: 1 immature - female, 11.6, fat. - - _Dendroica pensylvanica._ Chestnut-sided Warbler.--Weights: - 2 immature females, 8.1, 10.0, little fat. Only one specimen - from Kansas had been preserved previously although the - species is a regular transient in small numbers throughout - the state. - - _Dendroica castanea._ Bay-breasted Warbler.--Weights: 1 - adult male, 19.2, excessively fat; 1 adult female, 11.7, - little fat; 1 immature female, 11.2, moderately fat. Only 5 - specimens of this warbler have been taken previously in - Kansas, 4 in spring (Ruth, 1952:18-19) and 1 in fall. - - _Dendroica p. palmarum._ Palm Warbler.--Weights: 2 immature - males, 9.9, 10.9, moderately fat; 2 unsexed immatures, 9.1, - 9.4, moderately fat. This species has been taken in fall in - Kansas only once before (KU 26353, taken by Wetmore, at - Lawrence, on October 5, 1907), but probably occurs regularly - in both spring and fall migration. - - _Seiurus a. aurocapillus._ Oven-bird.--Weights: 2 adult - males, 22.5, 23.8, fat and very fat; 14 immature males, mean - 21.89 ± .66, S. D. 2.46, fat to very fat; 8 adult females, - mean 21.4 (18.3-25.7), moderately fat to fat; 6 immature - females, mean 18.2 (15.6-20.0), moderately fat to fat. - - _Seiurus noveboracensis notabilis._ Northern - Water-thrush.--Weights: 3 immature males, 18.1, 18.6, 22.2, - moderately fat to fat; 1 immature female, 22.2, fat. - Referring these birds to _notabilis_ is a somewhat arbitrary - procedure. They display some intermediacy of characters and - probably stem from a population, intermediate between - _notabilis_ and _noveboracensis_, occupying much of central - North America (cf. McCabe and Miller, 1933). - - _Oporornis philadelphia._ Mourning Warbler.--Weight data - presented elsewhere. The birds killed at Topeka provide the - latest fall dates for this species in Kansas. Fifteen were - killed on September 25, 64 on October 1, 2 on October 5, 11 - on October 6, 2 on October 7, and 1 on October 8. We find no - other records later than September 15. Of 93 specimens - examined, 1 was excessively fat, 22 were very fat, 45 were - fat, 21 were moderately fat, and 4 had little fat. The - abundance of this secretive species in the sample was a - great surprise. It had previously been considered a rather - rare migrant in this area. - - _Geothlypis trichas occidentalis [>brachidactyla?]._ - Yellow-throat.--Weight data presented elsewhere. This - species was second in numbers only to the Nashville Warbler - in the total kill at Topeka. Of 167 birds examined, 29 were - very fat, 114 were fat, 23 were moderately fat, and 1 had - little fat. - - The Yellow-throats are greatly in need of meaningful and - comprehensive revision, which to date has been restricted to - the western subspecies (Behle, 1950). Since the appearance - of the 1931 A. O. U. Check-List a great deal of scattered - taxonomic work on the species, as yet unsynthesized, has - made the picture of its geographic variation a blurry one so - far as the details are concerned. Made in the absence of - adequate comparative material, the above identification is - to be regarded as tentative. Also, it is, unfortunately, - based only on those 6 of our 176 specimens preserved as - skins. Five of these are adult males, the sixth being an - immature female. Compared with a series of Kentucky - specimens regarded as typical _brachidactyla_, these birds - are paler and brighter above (tending toward gray-green - rather than brownish olive), brighter and more extensively - yellow below, with broader, more nearly white superciliary - stripes above their black masks (in males). In size they are - close to _occidentalis_ (see Behle, 1950:202). Five males - have an average wing-length of 56.6 mm. (53-59); one female - measures 53. Six males from Kentucky: 55.1 (53-56); four - females, 51.1 (48-56). Our birds may be assumed to have - stemmed from a population to the north and west which, if - not _occidentalis_ (or _campicola_ Behle and Aldrich, of - which no comparative material is at hand), is intermediate - between _brachidactyla_ and more western birds. Judging from - Behle's map (1950:fig. 32), these birds may have come from - an area near the confluence of three subspecies - (_campicola_, _occidentalis_, _brachidactyla_). Long - (1940:452) reports three subspecies breeding in Kansas - (_brachidactyla_, northeast; _occidentalis_, west; - _trichas_, southeast). The occurrence in Kansas of _G. t. - trichas_ as currently understood is completely out of the - question. - - _Icteria v. virens._ Yellow-breasted Chat.--Weight: 1 - unsexed immature, 29.7, moderately fat. - - _Wilsonia p. pusilla._ Wilson Warbler.--Weights: 2 adult - females, 7.5, 7.8, fat, moderately fat; 1 unsexed adult, - 8.3, fat. - - _Wilsonia canadensis._ Canada Warbler.--Weight: 1 immature - female, 10.0, little fat. We know of only five other - specimens from Kansas, although this warbler seems to be a - regular migrant in small numbers in the state. - - _Setophaga r. ruticilla._ American Redstart.--Weight: 1 - immature female, 9.1, moderately fat. - - _Dolichonyx oryzivorus._ Bobolink.--Weights: 2 adult - females, 39.5, 42.9; 2 immature females, 38.8, 42.0; all - excessively fat. Specimens of the Bobolink previously have - been taken in fall in Kansas only on September 20 and 24, - 1933, near Lawrence, by Long and Preble (Long, 1934). - - _Pheucticus ludovicianus._ Rose-breasted Grosbeak.--Weights: - 1 adult male, 50.4, fat; one immature male, 54.5, very fat. - - _Passerina cyanea._ Indigo Bunting.--Weights: 1 adult male, - 18.4, fat; 2 immature males, 17.2, 17.2, fat and very fat; 2 - adult females, 14.3, 16.9, moderately fat and very fat; 1 - immature female, 13.4, little fat. The sample was carefully - checked for Lazuli Buntings (_Passerina amoena_); none was - found. - - _Spiza americana._ Dickcissel.--Weight data presented - elsewhere in this paper. Dickcissels were picked up at the - television tower on October 1 (31), 5 (1), 6 (3), and 7 (1). - These birds, together with an adult female taken 3 miles - east and 3 miles south of Lawrence, on October 11, 1953, by - Tordoff, are the only specimens of this species taken as - late as October in Kansas. The Dickcissel becomes - inconspicuous in late summer and many observers here and - elsewhere have thought the species disappeared much earlier - than it really does (see Ganier, 1949). Of 34 specimens, 20 - were very fat and 14 were fat. - - _Passerculus sandwichensis nevadensis._ Savannah - Sparrow.--Weights: 1 adult male, 19.4, fat; 2 immature - males, 18.3, 19.0, moderately fat; 5 adult females, mean - 17.2 (14.8-19.5), little fat to fat; 4 immature females, - mean 18.0 (16.9-19.6), moderately fat to fat. Many of the - Savannah Sparrows migrating through Kansas have in the past - been referred to the subspecies _P. s. anthinus_ (= - _alaudinus_ of the 1931 A. O. U. Check-List) by various - workers (see Long, 1940:454). As Peters and Griscom - (1938:464-5) have shown, true _anthinus_, breeding in the - far northwest, ordinarily occurs in migration only in the - western part of the country, the breeding Savannah Sparrows - of a large part of the central continental region (east to - southern Wisconsin) being _P. s. nevadensis_ as now - understood. Migrants of this pale, clay-colored subspecies - should be abundant in Kansas, and all of the specimens in - the present sample are referable to it. - - _Ammodramus savannarum perpallidus._ Grasshopper - Sparrow.--Weights: 3 adult males, 16.4, 17.6, 20.6, - moderately fat, fat, fat; 5 immature males, mean 18.1 - (16.0-20.2), little fat to fat; 5 adult females, mean 17.9 - (16.8-18.9), moderately fat to very fat; 5 immature females, - mean 18.1 (16.8-20.6), fat to very fat. - - _Passerherbulus caudacutus._ Leconte Sparrow.--Weights: 1 - immature male, 11.2, moderately fat; 1 immature female, - 12.2, moderately fat. - - _Ammospiza caudacuta nelsoni._ Sharp-tailed - Sparrow.--Weights: 2 adult males, 15.2, 17.1, moderately fat - and very fat; 1 adult female, 13.3, little fat. Five - specimens of this species have been taken previously in - Kansas, all in October in the eastern part of the state. - Additionally, several observers have reported birds seen but - not collected. The three birds from Topeka were picked up on - October 6, 7, and 10 and are the only specimens taken since - 1907. Possibly our specimens from Topeka struck the tower on - the same night. Tordoff noticed, upon preparation, that the - specimens from October 7 and 10 showed progressive drying of - the extremities and spoilage as compared with the bird - picked up on October 6. - - _Junco hyemalis cismontanus._ Slate-colored Junco.--Weight: - 1 immature female, 16.4, little fat. Juncos of hybrid type, - whether _J. h. hyemalis_ × _J. oreganus_ subsp. or true _J. - h. cismontanus_, are fairly common in eastern Kansas. - - _Spizella pallida._ Clay-colored Sparrow.--Weights: 2 adult - males, 11.6, 12.2, both fat; 1 immature male, 11.8, fat; 1 - adult female, 12.5, fat; 7 immature females, mean 11.1 - (9.7-12.5), little fat to fat. - - _Passerella iliaca iliaca._ Fox Sparrow.--Weight: 1 adult - female, 29.4, little fat. A trifle grayer above than any of - several Kentucky specimens, this bird nevertheless seems - well within the range of variation of _iliaca_. - - _Melospiza l. lincolnii._ Lincoln Sparrow.--Weights and - measurements are discussed elsewhere. Of 81 specimens, 15 - were very fat, 47 were fat, 12 were moderately fat, and 7 - had little fat. Interestingly, there is no evidence that the - large southern montane subspecies (_M. l. alticola_) has - contributed to the present sample. No bimodality is evident - in the curve of wing-length in our birds, the largest of - which barely approach, the small extreme recorded for - _alticola_ by Miller and McCabe (1935:156). - - _Melospiza georgiana ericrypta._ Swamp Sparrow.--Weights: 3 - immature females, 14.3, little fat, 16.7, 17.0, moderately - fat. Swamp Sparrows examined were all more or less brightly - colored and seem to belong to this northern subspecies. - - _Melospiza melodia juddi._ Song Sparrow.--Weights: 1 adult - female, 19.4, little fat; 1 unsexed immature, 16.0, little - fat. A large proportion of the migrant and wintering Song - Sparrows in eastern Kansas probably originate from the range - of this subspecies in the northern plains. _Melospiza - melodia euphonia._--One immature female (not weighed) was - picked up below the tower on October 27, 1954, and thus does - not appear in Table 1. The specimen proved typical of this - generally more eastern subspecies upon comparison with a - large series from Kentucky. For what it may be worth we - refer the single specimen to this subspecies. Long - (1940:456) reported two eastern subspecies from Kansas - ("_beata_," _melodia_). All Kansas specimens genuinely of - eastern origin probably originate from the range of - _euphonia_, as now understood. - - - - -Randomness of the Sample - - -The reliability of certain of the conclusions which might be drawn -from data of the kind presented herein depends largely on the -randomness of the sample. To what degree does this sample provide a -true cross-section of the nocturnal migrants present over the area on -a given night or succession of nights? As far as the relative -abundance of species in the sample is concerned, there is little doubt -that it is not at all random. The absence of such species as the -Gray-cheeked Thrush (_Hylocichla minima_), among the passerines, and -many of the shorebirds known to be migrating through the area at the -time is evidence for this statement. Quite possibly many seminocturnal -species did not strike the tower at all for the simple reason that -they could see it, and certain large-eyed diurnal species (such as -thrushes and shorebirds) may avoid collision to some extent, thus not -appearing in the sample in proportion to their actual numbers. -Finally, some or all of the species concerned probably migrate partly -by day. The sample may to some degree reflect the true relative -abundance of closely related species. For example, there is little -doubt that, as shown by the sample, Nashville Warblers are more -numerous locally at this season than Tennessee Warblers, a fact that -can readily be corroborated by ordinary field observation. Also, the -sample is useful in suggesting the actual abundance of species which -are furtive and/or difficult to identify under normal field -conditions, for example, the Mourning Warbler and Philadelphia Vireo. -It is obvious that the sample should reflect the true relative -abundance at one place and time of any two species with equal tendency -to migrate by night and equal tendency to strike the tower. Since the -facts in regard to both tendencies are at present unknown for most -species, we think that interspecific comparisons should be avoided or -approached with extreme caution. - -In respect to the relative abundance of the various sex- and -age-classes within a given species, the sample is, we think, as close -to random as is possible to obtain. Certainly it is greatly superior -to samples obtained by field collecting, where possible differences in -habits, wariness, and experience of the birds, and subconscious (if -not conscious) selection by collectors can all bias the results. -Dwight (1900:128-9) believed that the greater wariness of adult birds -was almost entirely responsible for the seemingly disproportionate -number of immatures in autumn and gave some observational evidence in -favor of his views. The large percentage of adults in some of the -samples here treated tends to reinforce Dwight's position. To a -somewhat lesser extent, this advantage in randomness of accidental -kills over routine collecting may be supposed to apply also in -demonstrating the composition by subspecies of a single migrant -species. - -So far as particulars already mentioned are concerned, the present -sample or other samples of tower-killed birds would seem to be in no -way superior (that is, more nearly random) to samples obtained in -connection with lighthouses and other lighted objects, and -ceilometers. In one important respect, however, it is probably -somewhat superior to these as the dimly red-lighted structure has not -been shown to have any important collecting or attracting influence. -Thus, in computations intended to estimate the over-all abundance of -migrants, the sample should be more reliable than samples involving -bright light with its possible attracting effect. - - - - -Number of Migrants - - -If it can be assumed that nocturnally migrating birds are -approximately uniformly spaced across the sky and that the red lights -did not attract birds which would otherwise have missed the tower, it -is possible to compute the volume of migration from the sample killed. -In regard to the first assumption, both Stone (1906:250-251) and -Lowery (1951:409-413) have presented evidence of fairly uniform -distribution of nocturnal migrants. We have no information on the -second assumption beyond the facts that birds do not strike the high -towers on clear nights or lower towers even on stormy nights. - -On nights when large numbers of birds struck the 950 foot Topeka -tower, only a few struck a 500 foot radio tower, also lighted with red -lights, at Lawrence, 24 miles east, under similar weather conditions. -Most of the birds found at Topeka were fairly close to the base of the -tower, indicating that they struck the tower itself or that they were -flying high enough to strike guy wires only fairly close to the tower. -The scarcity of birds under the guy wires some distance from the tower -at Topeka and at the radio tower at Lawrence causes us to think that -most of the birds were flying more than 450 feet above the ground. On -this basis, we have computed numbers of migrants passing through a -plane one mile long and 500 feet high (2,640,000 square feet), -intersecting the assumed path of migration at right angles. -Vertically, the theoretical plane begins at 450 feet above ground and -has its top edge at 950 feet. The solid (discounting spaces between -girders, _etc._) cross-sectional area of the tower intersecting this -plane was computed by actual measurement to be 1685 square feet. On -the night of September 30-October 1, 585 birds were killed. By -computation (585/1685 = X/2,640,000), approximately 916,000 birds -passed through the mile-long plane that night. On each of the nights -of October 5-6 and October 6-7, approximately 230,000 birds passed -through this plane. By comparison, Lowery (1951:436) recorded maximum -station densities in one night in spring of 63,600 birds at Tampico, -Mexico, and 51,600 at Lawrence, Kansas, as determined by -moon-watching. Lowery's figures refer to numbers of birds crossing any -part of a circle one mile in diameter and are roughly comparable to -ours if, as we think, most of the birds at Topeka were flying at -altitudes between 450 and 950 feet above the ground. - -It must be realized that these figures are only approximations. One -variable ignored is the frontal extent (or area, viewed from the -front, subject to damage by striking an obstruction) of the birds -themselves. Since practically all birds killed showed head or trunk -injuries, rather than a high proportion with only broken wings, we -chose to disregard frontal extent of the birds in our calculations. If -our figures are inaccurate by as much as 50 per cent in either -direction, which seems unlikely to us, they still give some idea of -the tremendous volume of nocturnal migration under some conditions. - -It may be more meaningful to compute numbers of migrants by species. -This can be done readily by making appropriate substitutions from -Table 1 in the equation given above. For example, on the night of -September 30-October 1, approximately 147,000 Nashville Warblers -passed through the mile-long plane and on the same night, 100,000 -Mourning Warblers and 14,000 Philadelphia Vireos. Neither of the last -two species would be judged to be abundant migrants in autumn in -eastern Kansas by ordinary field observations; the television tower -sample, however, indicates that these as well as other species must -often be overlooked when they do stop in Kansas. - - - - -Differential Migration of Sex- and Age-classes - - -HISTORY OF THE SUBJECT.--For a long time it has been known in a -general way that old and young birds and males and females of some -species do not always migrate at the same times, by the same routes, -or even to the same places. This is a subject about which much has -been written. Reading the summaries of some general texts, it is easy -to acquire the impression that the facts of the matter are well known. -On the contrary, they are poorly known and much remains to be learned -before differential migration is understood. This can best be -indicated by a brief survey of the literature. - -The importance of the subject was emphasized by Meinertzhagen -(1930:52) in one of the later reviews of differential migration: "The -main problem concerns the Cause of Migration, the Stimulus which -compels Migration and the Origin of the Migratory Habit.... There is, -however, a minor problem which affords valuable evidence in helping us -to solve the major problem, bearing very directly on it, namely, the -order of sex and age on migration." - -The mystery of how birds, especially the young, find their way in -migration has fascinated students since the earliest times. The quite -natural though purely anthropomorphic conclusion of early scholars was -that the old birds led the young on migration. This attractive idea -persisted long after ornithology began to grow into a science. The -classic theory was restated by Palmén (1876:267), in one of the first -thorough reviews of the subject of migration, as follows: "Directe -Beobachtungen in der Natur ergeben, dass die Schaaren von ziehenden -Vögeln allgemein ältere und stärkere Individuen als Anführer des Zuges -haben." Variously modified, this view continued to crop up for some -time and still found support in the 1890's (see Dixon, 1892:69). Gätke -(1895:101) correctly questioned the credibility of Palmén's "direct -observations." - -With the gradual abandonment of the unsupportable classic theory, -diametrically opposed views were adopted by workers on opposite sides -of the Atlantic. The American stand was ably expressed by Brewster -(1886), who went to great pains to state his case and give evidence, -and who was later supported by Allen (1896:144-147; 1909:17). The -Americans held that adult birds nearly always preceded the young in -migration, and this was based on much evidence, whether or not -correctly interpreted. Dwight (1900:127) also gave evidence in favor -of this theory. Equally definite, if, as has later been shown, -somewhat vaguely documented, was the famous work of Gätke (1895:see -pp. 100-113), who after many years' observation of migrant birds in -Heligoland concluded the exact opposite, that young in general precede -adults (see critiques of Allen, 1896:144-147; Wiegold, 1926:5). -Gätke's dissenting opinion was for a time supported enthusiastically -by British workers (Gurney, 1923:579-580). - -As so often happens, neither extreme has withstood the test of time, -and more recent summaries (Meinertzhagen, 1930:55-56; Thomson, 1926, -1936:488-489; Wiegold, 1926) have tended to compromise. Many -exceptions to Gätke's extreme conclusion have been detected. -Exceptions to the Brewster-Allen stand have also been discovered, -although work along these lines on the American side has lagged -somewhat. Rowan (1926) has given further evidence on the migration of -certain shorebirds, and some evidence has accrued in relation to -particular species and groups as a result of life-history and banding -studies (see Pitelka, 1946). Authors of major works on migration, -however, have either been preoccupied with other phases of migration -or avoided the issue. In an able study (one of several on related -subjects) of the composition by sex and age of migrant populations in -north Germany, Drost (1935:177) did not go into the question of order -on migration. - -One is left with the impression that the whole subject is still -unsettled. While earlier workers sought to reduce the entire matter to -law, the latest disclaim the possibility of generalization. After -summarizing Brewster's and Gätke's opinions, Thomson (1926:79) wrote: -"It would seem, in any event, that no general rule can be laid down." -Meinertzhagen's summation (1930:56-57) still represents fairly well -the status of our knowledge: "Order of sex and age on autumn passage -is very difficult to arrive at, as evidence is conflicting. But, on -the whole, it seems that birds flock together, old and young, -preparatory to moving south, and do in many cases initiate migration -in company.... But once movement is initiated, among birds which do -not habitually fraternise in flocks, adults, and especially males, -will naturally outstrip the less virile females and still less virile -offspring.... The consequence is that any observer at an intermediate -station such as Heligoland is, in noting birds of the year as first -arrivals, has not had an opportunity of noting the flocks of adults -which have passed without alighting. On the other hand, there is very -definite evidence to show that among certain species, adults follow -their offspring on migration. The reason for different behaviour -among different types of birds remains obscure." We regard much of -this as still theory. - -[Illustration: FIG. 1. Composition by age and sex as found in one or -more series of each of eight species of birds included in the Topeka -sample. Each separate series is represented by a single histogram, the -histograms for a species being grouped with the earliest series on the -left. Each histogram expresses the numbers of adults (left-hand -column) and immatures (right-hand column) in terms of percentage of -the whole series. Thus the two bars of each couplet add up to 100 per -cent. The hatched portion of each bar represents males, the clear -portion females.] - -It would be difficult to imagine a better way of resolving the -problems and uncertainties just reviewed than by the detailed -analysis of large samples of migratory birds killed at random at -various points and times. An analysis of the sample of birds -accidentally killed at Topeka is presented here as an initial step in -this direction. Although the conclusions based on this sample are -tentative and may in time be altered, the data themselves are -definite. If this general type of analysis is repeated again and -again--applied to samples taken on many dates and in many -localities--a mass of hitherto unparalleled evidence for the study of -migration will emerge. - - -DIFFERENTIAL MIGRATION OF SEX- AND AGE-CLASSES AS SHOWN BY THE TOPEKA -SAMPLE.--Smaller samples have not been treated. Species affording -samples seemingly large enough to justify at least preliminary -analysis were: Catbird, Red-eyed Vireo, Mourning Warbler, Dickcissel, -Nashville Warbler, Orange-crowned Warbler, Yellow-throat, and Lincoln -Sparrow (Fig. 1). For all of these except the Catbird and Dickcissel, -at least two samples from a week or more apart were available for -comparison in an effort to detect trends in migration. Fig. 1 shows -the actual ratios of sex- and age-classes observed in samples of the -species listed above. Each of the last four species provided two -separate samples, of sufficient size to warrant an attempt at -measuring the statistical significance of the observed changes in -adult-immature ratios (Table 2). - -TABLE 2.--STATISTICS OF THE RATIOS OF ADULTS TO IMMATURES IN FOUR -SPECIES - - ======================================================================= - Species | Dates |Total | Number | Differ- |P[3] - | of samples |number| and | ence | - | | |percentage |(in %)[2]| - | | |of adults[1]| | - --------------|--------------------|------|------------|---------|---- - Nashville |Oct. 1 (93) | 156 | 45 (.484) | .071 |.36 - Warbler |Oct. 5-7 (63) | | 26 (.413) | | - | | | | | - Orange-crowned|Sept. 25-Oct. 1 (19)| 44 | 3 (.158) | .282 |.05 - Warbler |Oct. 5-9 (25) | | 11 (.440) | | - | | | | | - Yellow-throat |Oct. 1 (115) | 159 | 62 (.540) | .085 |.34 - |Oct. 5-8 (44) | | 20 (.455) | | - | | | | | - Lincoln |Oct. 1-3 (44) | 71 | 27 (.614) | .318 |.01 - Sparrow |Oct. 6-10 (27) | | 8 (.296) | | - ---------------------------------------------------------------------- - - Footnotes: - - [1] Percentage of immatures equals 1.000 minus percentage of - adults. - - [2] Standard error of the difference between ratios was - computed by the formula - [Greek: s]^e = sqrt(P_e Q_e (1/N_1 + 1/N_2)) - where P_e equals percentage of adults and Q_e equals - percentage of immatures in the entire sample. - - [3] Probability of error; _i. e._, a P of .01 means there is - one chance in 100 that the difference observed does not - represent an actual difference in nature. - -Upon the application of statistical methods it soon became evident -that, unless changes in ratio between two samples are marked, large -samples would be required in order to reach conclusions of high -statistical significance in a single study of the present type. In -this case (see Table 2), the Lincoln Sparrow and Orange-crowned -Warbler, though represented by only moderate-sized series, show marked -changes in age composition over the period studied, and the -statistical treatment indicates a high degree of probability that -these changes are real. Assurance that the lesser changes observed in -the Nashville Warbler and Yellow-throat are real, on the other hand, -is much less, even though the samples are larger. Few if any of the -samples here discussed are as large as might be desired. Therefore, -conclusions based upon them (see below) are to be regarded as -tentative. Many other, future, samples will perhaps also be -insufficient in size in themselves. There are, however, statistical -advantages to repetition which will serve to make the repeated -analysis even of small samples significant and valuable. - -Certain of the samples not treated statistically show ratios that can -be seen by inspection to be probably significant. For example the -almost complete absence of adults from the three samples of Red-eyed -Vireos (Fig. 1E) cannot be disregarded in view of the size of the -whole sample of the species. The same applies to the high percentage -of adult females and the near absence of adult males in the sample of -the Dickcissel (Fig. 1F). The continuity in direction of changes -observed in the three samples of the Mourning Warbler (Fig. 1G) and -Red-eyed Vireo is likewise probably significant, even though some of -the samples compared are small. It seems to us that the application of -statistical methods to these species should await the accumulation of -more material. For anyone desiring to treat them statistically now, -the data are inherent in this paper. - -We have not computed the standard errors of the ratios of sexes within -age groups (except experimentally in a few cases). This can easily be -done, however, and the significance of a given ratio determined, on -the assumption (perhaps sometimes dubiously justifiable) that the -sex-ratio in the species concerned is one:one. Obviously there is no -point in computation of the standard errors of adult-immature ratios -in single samples (such as that of the Dickcissel) until the actual -ratio prevailing in the species in nature at the season in question is -known for comparison with the observed ratio. Our formal statistical -treatment, therefore, has been limited to an examination of the -significance of the _changes_ between adult-immature ratios in samples -of the same species taken a number of days apart. - -The samples suggest several patterns of differential migration of sex- -and age-classes. Indeed, the important consideration brought out--in -our opinion not hitherto sufficiently emphasized in literature--seems -to be that in generalizing about adults and immatures, one must be -careful to take sexes into account, and conversely, in generalizing -about males and females, one must consider also age. In other words, -there are really four classes to be considered. This poses additional -problems in analysis and introduces the need for still larger samples -in order to reach significant conclusions. To illustrate: an -adult-immature ratio of 40:20 (N = 60) may be satisfactorily -significant, while within the 40 adults a ratio of 25 males:15 females -may not be. Were the original sample 80:40 (N = 120) with male adults -50 and female adults 30, it is obvious that the significance of the -latter ratio would be greater. The same applies in reverse if the -greater emphasis is placed on sex and the lesser on age. Because of -the moderate size of the samples this problem has been felt in the -present study in respect to sex ratios within age groups, many of -which must at present be regarded as of tentative significance. - -In short, what the earlier ornithologists regarded as a simple problem -is in reality a complex one. There are only two patterns in what may -be called the Brewster-Gätke argument: adults first or immatures first -(with of course the further possibility of both at the same time). -Both patterns occur, as is now known, at least to some extent. But -actual patterns, as suggested by our samples, are more complex when -all classes are considered. It will readily be seen that, if adult -males, immature males, adult females, and immature females be regarded -as units, each with certain migratory characteristics, the -combinations of these units in various orders of migratory precedence -are potentially numerous. In fact, of course, they do not behave -strictly as units (or perhaps very rarely so), but our data strongly -indicate that the tendency exists in many cases. This may be stated -another way. The present samples may be reduced to two basic patterns, -fitting the classic early American (adults first) and early European -(immatures first) theories. But, either such simple arrangement is -compounded in some, perhaps in truth in all, instances by differential -migration of the sexes _within_ each age class. This proposition can -also be stated backwards: the samples show differential times of -migration of the sexes, compounded by differential times of migration -of the age groups within each sex. The order in which these matters -are approached depends on what one is trying to find out. Influenced -by the literature, in which most emphasis has been placed on age, we -have approached the problem from that standpoint. The data and figures -here given, however, can be juggled if one wishes to place first -emphasis on the order of sexes in migration. - -Bearing in mind what has just been said, particularly in respect to -sizes of samples necessary for significance, let us consider the -patterns of migration suggested by the Topeka sample. These are as -follows: - -(1) _An early migration largely composed of adults, giving way later -on to a preponderance of immatures._ Regardless of variations among -them, samples showing this basic pattern are in line with the opinions -of Brewster (1886) and his followers. This pattern is here shown by -the Lincoln Sparrow, Yellow-throat, Nashville Warbler, Catbird (one -sample only), and Red-eyed Vireo (Fig. 1, A, B, C, D, E). The evidence -of these and all other samples would admittedly be more conclusive if -the samples were further apart in time or, better still, were there -more of them. There is evidence that differences in migration of the -sexes, within age classes, influence this pattern, sharply in some -instances. In the later samples of Lincoln Sparrow, Yellow-throat, and -Red-eyed Vireo (Fig. 1, A, B, E) there are relatively fewer males, -both adult and immature, than in the earlier samples and this may be -true also of the Catbird, judging from the single sample. The Red-eyed -Vireo (Fig. 1, E) is characterized by small number, or absence of, -males in each sample but the samples are not significantly different, -and can be regarded as one. Although the samples of the Dickcissel and -Mourning Warbler (Fig. 1, F, G) show a somewhat different over-all -pattern and are discussed further on, they also contain few adult -males. Since these samples are from a period that is near the end of -the migration of Red-eyed Vireos, Mourning Warblers, and Dickcissels, -it may be assumed tentatively that the adult males have already -migrated. Meinertzhagen (1930:56) postulated that in many species -there is an earlier or more rapid migration of adults, particularly -males, and the data for the above species in our sample tend to -support his assumption. But our data suggest in addition that in some -species _immature males_ migrate earlier, or more rapidly, than do -_immature females_, just as adult males precede adult females in some -instances. Within this general pattern (adults first) another -variation is shown by the Nashville Warbler (Fig. 1, C) in which the -later sample of adults is heavily weighted towards males, even though -an increasing over-all proportion of immatures is evidenced. In this -case, and contrary to Meinertzhagen's suggestion, it would seem that -adult females have preceded or outstripped adult males in migration. - -(2) _An early preponderance of immatures, followed by a preponderance -of adults._ The several species of birds at Topeka that display this -pattern conform with the conclusions of Gätke and other early Old -World ornithologists that in most species immatures precede adults in -migration. In the present sample two variations of this pattern occur. - -(a) In the Dickcissel (Fig. 1, F) and the Mourning Warbler (Fig. 1, -G), immatures decrease more markedly than adults (visible in samples -of Mourning Warbler; inferred in Dickcissel), leaving the adults in -the majority in the closing phase of migration. The distinctive and -interesting feature in each of these two species is the ascendancy in -numbers of adults _despite_ the almost complete disappearance of adult -males. The relative increase of adults is here caused by a retarded -migration of adult females, which linger conspicuously behind all -other classes. Something of this nature was suggested, in theory, by -Dixon (1892:70) who thought that adult females are delayed by -"maternal duties." It was hinted at also by Dwight (1900:127) who -thought that in some species females molted later than males as a -result of prolongation of parental responsibilities. As mentioned -already, there is need for caution in interpreting the present samples -because the Dickcissel is represented only by one sample and two of -the three samples of Mourning Warblers are small. In the case of the -Mourning Warbler, the samples may be regarded as one, nearly lacking -in adult males. The progressive increase of adult females, however, -may be significant; at least there are enough of these to make -division of the birds into three samples enlightening. There is, of -course, some chance that the majority of adult males have not yet -migrated, or are migrating by a different route. This seems unlikely -in both cases. October 1 is late in the migration of the Dickcissel -and it seems that large-scale migration would not occur much later, -and in the case of the Mourning Warbler adult males are rare in all -three samples, extending over a considerable period and reaching late -into the probable migration period of the species. It is interesting -to conjecture just when and where adult male Mourning Warblers do -migrate in autumn. Brewster (1886:16) wrote: "This species arrives at -Cambridge [Massachusetts] about September 12, and during the remainder -of the month is ... abundant.... The adults, however, are so very -uncommon that I have never known them [to] represent more than five -per cent of the total number of individuals. They do not seem to be -more numerous in the earlier flights than towards the close of the -month, and I am very sure that they cannot be found in this locality -before the young begin to appear." While the present samples show an -abundance of adult _females_ of this species (could Brewster have -failed to recognize these as adults?) the whereabouts of the adult -males remains a mystery. - -(b) Another variation is displayed by the Orange-crowned Warbler (Fig. -1, H). Here also there is an increase of adults towards the end of -migration, but this increase is marked by a growing percentage not of -females but of males. Locally this species is a late migrant compared -with most others of the Parulidae. Thus the first sample, composed of -birds taken September 25-October 1, may be regarded as fairly early in -the fall migration. Immature birds compose 84.2 per cent of this -sample, there being no adult males at all. By October 5-9 the picture -has changed markedly, the sample being composed of 44 per cent adults -(82 per cent of which, in turn, are males) and 56 per cent immatures. -In view of this trend one can not help suspecting that a still later -sample would show a majority of adults, perhaps nearly all males. This -of course does not necessarily follow; the migration of immatures -could simply be more protracted, and could have commenced earlier, -than that of adults. - -Little imagination is required to see how enlightening it might be -could we analyze thoroughly the patterns of all migrating species. -When the detailed facts are available, it seems likely that general -trends will emerge which may be of great significance to the study of -migration in general. A final point which must eventually be clarified -is determination of the extent of variability in the pattern of each -species from year to year and locality to locality. - -Once patterns of precedence in migration of different classes are -established, search into the life-histories of the species concerned -may help to explain the peculiarities discovered. In the present case, -for instance, we find a possible clue to the reason for the high -proportion of adult females of the Dickcissel late in migration, as -shown by our sample. Gross (1921:14-15) presented evidence that adult -female Dickcissels molt considerably later than their mates, and we -have independent evidence that individuals of this species are at -times almost flightless when molting the remiges! - - - - -Molt in Relation to Migration - - -GENERAL COMMENT.--The exact relationship between molt and migration -seems not to have been definitely established. The subject has -received cursory attention in the literature and conflicting opinions -have been expressed. Dwight (1900:126-128) believed that molt is -completed or nearly completed before migration in nearly all passerine -species that occur in New York save for certain swallows and -flycatchers. Molt has since been found to precede migration of at -least one of the flycatchers (_Empidonax virescens_) considered by -Dwight to be an exception to this rule (Mengel, 1952). In Great -Britain the subject of molt in migration was considered in some detail -by Rintoul and Baxter (1914) and Ticehurst (1916), who arrived at -conclusions similar to Dwight's. These workers also found certain -swallows to be exceptions to the rule. - -The above authors and others have shown that, at least among -passerines, some body molt is frequently found in migrating -individuals but that molt of tail feathers is much less often found -and molt of remiges almost nonexistent. Baxter and Rintoul noted only -four cases of molting wing feathers among hundreds of migrants. Among -the diverse non-passerine orders the picture seems to be more -complicated, as might be expected. We do not, however, comprehend the -reasoning which led Meinertzhagen (1930:56) to summarize: "... on the -whole it can be said that though birds seldom migrate when flight -feathers are in quill, moult in general does not influence migration." -This seems to us an obvious _non sequitur_. Meinertzhagen (_loc. -cit._) went on to say: "Males and females of one species are believed -to moult simultaneously [see, however, Dwight, 1900:127], and there is -no doubt that in some cases the two sexes migrate at slightly -different times, and occasionally prefer different winter quarters. -Birds of the year never moult their quills previous to their first -autumn migration [Consultation of Dwight, 1900, who gives many -examples of this, would have spared Meinertzhagen this error.], and -yet they frequently follow adults on passage and sometimes precede -them. There are no grounds for believing that adults have moulted -their quills before birds of the year are prepared to migrate [but -there are, in many cases; _cf._ Dwight, 1900:127], in the case where -adults precede the latter. Neither is there any evidence to show that -adults have not moulted their quills till after their offspring are -ready for passage, in the case where they follow their offspring. It -does not, therefore, appear that moult is an important factor." - -Comments interpolated above show our feeling that this summary is -inadequate and misleading. To us it seems that the extreme rarity in -migration of birds with remiges in molt is strong evidence that molt -_does_ influence at least the time of migration. It is immaterial -whether this molt occurs before or after migration, although in the -majority of cases it seems to take place before. Much more needs to be -known of the migration pattern and molt of each species before -generalizations can safely be made. - -Analysis of samples of migrants can show only the presence and nature -or the absence of molt in birds actually migrating. In the present -instance shortage of time and manpower for preserving some and -processing all of the sample resulted in incomplete data being kept on -molt. We include this section to emphasize uncertainties still -prevalent and to stimulate further work. - - -MOLT IN THE TOPEKA SAMPLE.--Our limited findings coincide with those -of Rintoul and Baxter (1914). Body molt was noted in a number of -individuals and species. When present, this molt almost invariably was -in its final stages. One immature male Rose-breasted Grosbeak (October -1) was in heavy body molt. It is perhaps worthy of mention here that -this grosbeak evidently migrates at times in extensive molt. An adult -male (RMM 1102) taken by Mengel near Henderson, Kentucky, on September -9, 1949, was molting plumage of body, wings, and tail, no feather of -the last being longer than one half inch. This remarkable specimen had -only five primaries on one side and four on the other fully -functional. The outermost on the left and two outermost on the right -were from the previous plumage, not yet dropped; the three innermost -of each wing were new and full-length. - -In the present sample molt of remiges was noted in one specimen, an -adult female Indigo Bunting (October 1) with outer primaries sheathed -and with molt in progress in the body plumage. The one (immature) -Yellow-breasted Chat in the sample (October 1) had all of its tail -feathers nearly full-length but in quill, possibly as a result of -accident, and two feathers were being replaced also in the tail of an -immature Clay-colored Sparrow (October 6), which was also in body molt -and had some, juvenal feathers on the belly and flanks. - -Body molt near completion was further noted as follows: immature male -Yellow-throated Vireo (October 1), adult male Blue-headed Vireo -(October 1), immature female Leconte Sparrow (October 23), several -Lincoln Sparrows (various dates). - - - - -Size Differences according to Sex and Age - - -LINEAR MEASUREMENTS.--Taxonomists long have recognized in many species -that males differ in size from females. Less attention, until -recently, has been paid to the relative sizes of adult and immature -birds. Many taxonomists, however, seem to have had an uneasy suspicion -that immature birds are "untrustworthy" in comparison with adults, and -immatures have often been excluded from samples when recognizable. -Since, however, there are still relatively few reliably aged specimens -in collections, for the most part only those immature birds -immediately recognizable as such by obvious plumage differences (which -are often present only in juvenal plumage) have been excluded from -series. The majority of birds in first winter plumage so closely -resemble adults that the two ages have been included in series for -measurement. In most passerines these younger birds still bear the -juvenal feathers in wing and tail and are, in size of these important -parts, quite as "untrustworthy" as birds still in juvenal body -plumage. Even if a complete postjuvenal molt occurs we still should -not assume that first winter feathers are as long as adult winter -feathers without first determining that this is so. Although aware of -this problem, systematists until recently seemingly have been more or -less content to disregard it, or forced to do so for practical -reasons. Miller (1941:179) had little choice but to hope that size -differences between adult and immature juncos were unimportant. Behle -(1942:217) wrote of Horned Larks, _Eremophila alpestris_: "... the -plumages of first-year birds and adults seem indistinguishable, though -I have never quite satisfied myself that there are no differences in -lengths of rectrices and remiges." He added, with logic confusing to -us: "Since it is a difficult problem to determine the ages of horned -larks that have passed the postjuvenal molt, this similarity of -plumages is fortunate for the systematist." - -In recent years, some workers have analyzed size differences between -adults and immatures. Sibley (1950:115) showed that adult Red-eyed -Towhees (_Pipilo erythrophthalmus_) had notably longer wings and tails -than immatures, and the same was demonstrated in Red Crossbills -(_Loxia curvirostra_) by Tordoff (1952). In work with jays -(_Aphelocoma_), Pitelka (1951:199) found that: "... in comparisons of -dimensions of sex and age groups within a given sample, although -magnitude of difference varies from one character to another, most of -the averages are successively smaller for first-year males and adult -and first-year females." He listed exceptions and concluded: -"Segregation [of sex and age classes] has proved to be of extreme -significance in an interpretation of individual and geographic -variation." - -Much along these lines can be learned by examination of large random -samples such as that afforded by the Topeka accident. Although only a -few species in this sample were measured, the results secured seem to -show further the need for segregation of age classes in taxonomic work -with some species. - -Figure 2 shows the variation in the lengths of wing and tail in the -Nashville Warbler. It is evident from the figure that in both of these -characters the four sex- and age-classes differ significantly. An -accurate idea of geographic variation in this species could not be -obtained without separating these classes in comparisons. Age classes -in spring and summer, long after the skull is completely ossified, can -be segregated only if differences in plumage can be found. In the -Nashville Warbler, such differences occur in fall (see annotated list) -but these probably are obliterated by the partial prenuptial molt. -These facts emphasize the importance, for taxonomic studies, of aged -specimens collected in late summer or early fall on their breeding -ground and in fresh winter plumage. Figure 3 shows the variation in -length of wing in the Lincoln Sparrow in which age seems to be of much -less importance than in the Nashville Warbler. Males and females of -the Lincoln Sparrow differ significantly in wing-length, but adults -and immatures are of nearly the same size. It would seemingly not be -necessary to separate age classes in studies of geographic variation -in the Lincoln Sparrow. Size data for some other species are given in -the annotated list. - - -WEIGHTS.--Little seems to have been done to determine the correlation -of weights with sex- and age-classes. Weight may be the best single -index of over-all size and is especially useful to students of the -physiology of migration. Weight, however, is subject to the -considerable variable imposed by fat condition. In large and -comparable series, this variable is probably removed insofar as -comparability of means is concerned, but the high variability of -weight in most cases naturally results in more overlap (less -separability) between populations with means close together than is -found with most linear measurements. - -[Illustration: FIG. 2. Statistics of variation in length of wing and -tail in the Nashville Warbler. The solid lines represent the observed -ranges in millimeters. The stippled boxes represent two standard -errors ([Greek: s]m) to each side of the means (vertical lines). The -open boxes represent one standard deviation ([Greek: s]) to each side -of the means.] - -[Illustration: FIG. 3. Statistics of variation in length of wing in -the Lincoln Sparrow.] - -Figures 4-6 show variation in weight in the samples of Nashville -Warbler, Mourning Warbler, Yellow-throat, Dickcissel, and Lincoln -Sparrow. Each figure is essentially self-explanatory. It will be seen -that in the Nashville Warbler and Lincoln Sparrow, weight is roughly -proportional to wing-length (shown in figs. 2 and 3), giving about -equally good separation of sex- and age-classes in the latter and -poorer separation in the former. Data for these and other species -indicate a generally greater weight of males than of females, but less -difference according to age. In some other species, for example the -Yellow-throat, immatures seem to be a little heavier on the average -than adults. It is unfortunate that wing-lengths are not at present -available for these. - -[Illustration: FIG. 4. Statistics of variation in weight in the -Nashville Warbler and Mourning Warbler.] - -[Illustration: FIG. 5. Statistics of variation in weight in the -Yellow-throat and Dickcissel.] - -[Illustration: FIG. 6. Statistics of variation in weight in the -Lincoln Sparrow.] - -These comments on weight suggest an additional factor which may play a -part in rate of migration and which some day may be profitably -studied. Suppose that in some species adults and immatures are nearly -the same in weight but that immatures have shorter wings. In such a -species the immatures are relatively shorter-winged for their weight -than adults. In aerodynamic terms, they would have a higher -"wing-loading." (Wing-loading is the result obtained by dividing area -of effective wing by total weight; it is here assumed that in a single -species wing area is directly proportional to wing length.) This being -the case, immatures with higher "wing-loading" would require more -energy (derived from fat) to fly the same distance as adults, or with -the same amount of fat they would fly a shorter distance. Thus they -might tend to be outstripped in migration by adults starting at the -same time. The reverse, of course, would also be theoretically true, -if adults possessed a higher wing-loading than immatures. Physical -factors such as these rather than the differential "virility" -postulated by Meinertzhagen (1930:56) might account for the arrival of -certain classes of some species on the wintering grounds in advance of -others. There are, of course, many other factors which must be taken -into account before the effect, if any, of the wing-loading factor can -be evaluated. Data for illuminating calculations will become -available, however, with the accumulation of abundant information on -weights, measurements, and migration patterns. - - - - -Computations of Longevity and Survival - - -Tanner (ms., and letter, April 21, 1955) recently devoted considerable -ingenuity to computing by actuarial methods the longevity of the -Oven-bird, using the adult-immature ratio in samples killed at a -ceilometer at Knoxville, Tennessee. Tanner's computations were based -on the simple assumption that - -S (survival rate) = Number of adults in population (or sample) / Total -size of population (or sample). - -Further application of such techniques may prove desirable and -rewarding. It would seem at present, however, to be a risky procedure, -as it has been abundantly shown (see above) that adults and immatures -often do not migrate at the same times and rates, and the ratios of -adults to immatures in samples of migrants are likely to be far from -representative of the true proportions in the populations concerned. -It should be added that Tanner is perfectly aware of this objection. - - - - -Processing of Samples - - -Thorough processing of large samples of birds killed accidentally is -time-consuming. We were fortunate in having considerable assistance; -even so, all desirable data could not be obtained from the 1090 birds -of the present sample. As aids to others conducting studies of this -kind we should mention a few points which may be of assistance. - -Birds should be picked up as soon as possible after death, certainly -by the end of the day after the accident and preferably much sooner. -They should be weighed as soon as possible after collection (weights -decrease rapidly, even under refrigeration), and the weights (in -grams, to one tenth of a gram) written on tags attached to a leg of -each specimen. The sample should then be sorted by species or groups -of species of approximately equal size (to avoid crushing of smaller -birds by larger ones), placed in boxes, paper bags, or better, -air-tight containers clearly marked with date, locality, and other -necessary particulars, and relegated to a deep-freeze compartment. For -all but the smallest samples, such freezing units are indispensable to -complete study. Once frozen, the birds may be selected for study at -leisure, but time is still important, as, even when frozen, gonads may -eventually deteriorate, and birds eventually become desiccated which -is a disadvantage if skins are to be made. - -In the cases of large kills, or limited manpower, or both, it may be -impossible to process all birds, however desirable this might be. If -possible, however, all should be collected, identified, the numbers -and species recorded, and rarities saved. Further, partial analysis, -or more properly, complete analysis of a partial sample, can be made. -Analyses which for any reason require randomness of sample pose a -special problem. We think that in very large kills the best way to -solve this problem is probably to make one or more transects across -the area where dead birds are found. These transects should cross both -the areas of greatest and least density (to allow for fast and slow -flying species). Their width may be adjusted to give the desired -number of birds, that is, the number that can be adequately processed. -Another alternative would be to decide to study certain abundant -species and pick up all of these. There are other possibilities, but -in any event the method of sampling should be thoroughly described -wherever all birds have not been processed. - - - - -Summary - - -The foregoing paper discusses accidents in which large numbers of -night-migrating birds are killed. A brief historical review of -ornithological interest in such occurrences is given, and the types of -data provided by the accidents are listed and discussed. In -particular, recent accidents occurring in early October, 1954, through -much of eastern United States are cited, and detailed analysis is -presented of a sample of 1090 birds killed one mile west of Topeka, -Shawnee County, Kansas, between September 25 and October 23, 1954. - -At Topeka during the period mentioned, 1090 birds representing 61 -species were collected and were processed at the University of Kansas. -For all specimens, weight, sex, age, and fat condition were recorded, -and certain species were measured as well. Some notes on molt were -taken. A total of 193 birds was preserved as study skins, and 49 as -skeletons. Comments on weight, size, sex, age, subspecific identity, -and status in Kansas are presented in an annotated list. - -Randomness of this and other similar samples is discussed. A -theoretical computation is given for several nights of the numbers of -migrants passing through a plane one mile in width, from 450 to 950 -feet above ground level, and oriented to face the arriving migrants. -The computed totals give some idea of the tremendous volume of -nocturnal migration under some conditions. Potentialities of further -study of such events are discussed and a comparison is made with lunar -observations. - -Differential migration of sex- and age-groups as shown by the larger -samples taken at Topeka (Catbird, Red-eyed Vireo, Nashville Warbler, -Yellow-throat, Mourning Warbler, Dickcissel, Lincoln Sparrow) is -discussed and the history of theories on this subject reviewed. It is -shown that age and sex must both be taken into account in studies of -differential migration. Several patterns of migration are displayed by -the species analyzed, adults migrating earlier than immatures in some -instances, young earlier than adults in others, but all seemingly -being complicated to varying degrees by differential migration of -sexes within age groups. It is suggested that explanations of these -patterns may be sought in the life histories of the species involved. - -Molt in relation to migration is discussed briefly, and it is held -that there is an important relationship between molt and time of -migration. Specimens noted to be in molt are listed. - -Size differences, in wing length, tail length, and weight are -discussed in relation to sex and age, and variation in one or more of -these characters is analyzed as found in the Topeka samples of -Nashville Warbler, Mourning Warbler, Yellow-throat, Dickcissel, and -Lincoln Sparrow. It seems that in some instances significant size -differences prevail between adults and immatures and that these age -classes should be separated in taxonomic work with species where -differences in size are known to exist. When the facts are not known -they should be determined, and the large samples collected in -accidents to nocturnal migrants present excellent opportunities for -ascertaining the facts. - -Other uses of material obtained in large migration accidents are -discussed, such as computations of longevity and the problems of -processing large, accidentally-killed samples. Care should be taken to -select samples as nearly random as possible when all birds cannot be -processed. - -Repeated and thorough analysis of accidental kills should provide a -mass of valuable data bearing on many questions and problems which -have thus far been little studied. - - - - -Literature Cited - - -ALLEN, J. A. - - 1880. Destruction of birds by light-houses. Bull. Nuttall - Orn. Club, 5(3):131-138, July. - - 1896. Gätke's 'Heligoland.' Auk, 13(2):137-153, April. - - 1901. Barrington's 'The Migration of Birds at Irish Light - Stations.' [Review.] Auk, 18(2):205-206, April. - - 1909. An American's views of bird migration. Brit. Birds, - 3(1):12-19, June 1. - -BARRINGTON, R. M. - - 1900. The migration of birds as observed at Irish - lighthouses and lightships [_etc._]. London, R. H. Porter; - Dublin, Edward Ponsonby. Pp. XXV, 285, 667. (Not seen; - citation from Mullens and Swann, Bibliogr. Brit. Orn., 1917, - p. 43 and Zimmer, Cat. Ayer Coll., I, p. 40, 1926; see also - reviews, Ibis, 1900:677-679, Auk, 1901:205-206; some sources - list pagination as XXV + 667, possibly in error.) - -BEHLE, W. H. - - 1942. Distribution and variation of the Horned Larks - (Otocoris alpestris) of western North America. Univ. - California Publ. Zoöl., 46(3):205-316, May 20. - - 1950. Clines in the Yellow-throats of western North America. - Condor, 52(5):193-219, September-October (September 25). - -BREWSTER, W. - - 1886. Bird migration. Mem. Nuttall Orn. Club, No. I, pp. - 1-22, Cambridge, March. - -CARSON, L. B. - - 1954a. [Destruction of birds at a television tower at - Topeka, Kansas.] Topeka Aud. News, 9(1):pp. = 1-2, July, - August, September [published October]. [Unsigned, unpaged, - and untitled article by L. B. Carson, ed.] - - 1954b. [Further destruction of birds at a television tower - at Topeka, Kansas.] Topeka Aud. News, 9(2):pp. = 5-7, - October, November, December [published December]. [Unsigned, - unpaged, and untitled article by L. B. Carson, ed.] - - 1954c. New records for fall migrants in eastern Kansas. - Kansas Orn. Soc. Bull., 5(4):27-29, December. - -DIXON, C. - - 1892. The migration of birds. London, Chapman and Hall. Pp. - XVI + 300. - -DOBBEN, W. W. H. VAN, and M. F. BRUYNS - - 1939. Zug nach Alter und Geschlecht an niederländischen - Leuchttürmen. Ardea, 28:61-79, December (not seen; see Auk, - 1940:271). - -DROST, R. - - 1935. Ueber das Zahlenverhältnis von Alter und Geschlecht - auf dem Herbst-und Frühjahrszuge. Vogelzug, 6(4):177-182, - October. - -DWIGHT, J., JR. - - 1900. The sequence of plumages and moults of the passerine - birds of New York. Annals New York Acad. Sci., 13(1):73-360, - October 19. - -GANIER, A. F. - - 1949. The late summer Dickcissel departure. Migrant, - 20(3):52-53, September. - -GÄTKE, H. - - 1895. Heligoland as an ornithological observatory. - Translated by Rudolph Rosenstock. Edinburgh, David Douglas. - Pp. X + II + 599 + 11 II. (advt.). - -GROSS, A. O. - - 1921. The Dickcissel (Spiza americana) of the Illinois - prairies. Auk, 38(1):1-26, January 18 (first of two parts). - -GURNEY, J. H. - - 1923. Bird migration as observed on the east coast of - England. Ibis, 11th ser., 5(4):573-603, October 3. - -HOWELL, J. C., LASKEY, A. R., and J. T. TANNER - - 1954. Bird mortality at airport ceilometers. Wilson Bull., - 66(3):207-215, September [published October 29]. - -HOWELL, J. C., and J. T. TANNER - - 1951. An accident to migrating birds at the Knoxville - airport. Migrant, 22(4):61-62, December. - -LASKEY, A. R. - - 1951. Another disaster to migrating birds at the Nashville - airport. Migrant, 22(4):57-60, December. - -LONG, W. S. - 1934. Notes from eastern Kansas. Auk, 51(2):255, April 4. - -1940. Check-list of Kansas birds. Trans. Kansas Acad. Sci., -43:433-456. - -LOVELL, H. B. - - 1952. Catastrophe to birds at a Louisville airport. Kentucky - Warbler, 28(1):5-6, February. - -LOWERY, G. H., JR. - - 1951. A quantitative study of the nocturnal migration of - birds. Univ. Kansas Publ., Mus. Nat. Hist., 3(2):361-472, - June 29. - -MCCABE, T. T. - - 1943. An aspect of collectors' technique. Auk, - 60(4):550-558, October 7. - -MCCABE, T. T., and A. H. MILLER - - 1933. Geographic variation in the Northern Water-thrushes. - Condor, 35(5):192-197, September-October (September 15). - -MEINERTZHAGEN, R. - - 1930. Nicoll's birds of Egypt. Vol. I (of 2). London, Hugh - Rees Ltd. Pp. XVI + 348. - -MENGEL, R. M. - - 1952. Certain molts and plumages of Acadian and - Yellow-bellied flycatchers. Auk, 69(3):273-283, July 7. - -MILLER, A. H. - - 1941. Speciation in the avian genus Junco. Univ. California - Publ. Zoöl., 44(3):173-434, May 24. - -MILLER, A. H., and T. T. MCCABE - - 1935. Racial differentiation in Passerella (Melospiza) - lincolnii. Condor, 37(3):144-160, May-June (May 15). - -PALMÉN, J. A. - - 1876. Ueber die Zugstrassen der Vögel. Leipzig, Wilhelm - Engelmann. Pp. VI + 292 + I. - -PETERS, J. L., and L. GRISCOM - - 1938. Geographical variation in the Savannah Sparrow. Bull. - Mus. Comp. Zoöl., 80(13):445-478, January. - -PITELKA, F. A. - - 1946. Age in relation to migration in the Blue Jay. Auk, - 63(1):82-84, January 25. - - 1951. Speciation and ecologic distribution in American jays - of the genus Aphelocoma. Univ. California Publ. Zoöl., - 50(3):195-464, July 20. - -RINTOUL, L. J., and E. V. BAXTER - - 1914. Notes on some passerine birds found migrating in - moult. Scottish Naturalist, no. 35, pp. 245-252, November. - -ROWAN, W. - - 1926. Notes on Alberta waders included on the British list. - Part II. Brit. Birds, 20(2):34-42, June 1. - -RUTH, E. L. - - 1952. The Bay-breasted Warbler in Kansas. Kansas Orn. Soc. - Bull., 3(3):18-19. - -SIBLEY, C. G. - - 1950. Species formation in the Red-eyed Towhees of Mexico. - Univ. California Publ. Zoöl., 50(2):109-194, November 24. - -SPOFFORD, W. R. - - 1949. Mortality of birds at the ceilometer of the Nashville - airport. Wilson Bull., 61(2):86-90, June. - -STONE, W. - - 1906. Some light on night migration. Auk, 23(3):249-252, - July. - -STORER, R. W. - - 1951. Variation in the Painted Bunting (_Passerina ciris_), - with special reference to wintering populations. Occas. - Papers Mus. Zool., Univ. Michigan, no. 532, pp. 1-12, June - 29. - -THOMSON, A. L. - - 1926. Problems of bird-migration. Boston and New York, - Houghton Mifflin Company. Pp. XV + I + 350. - - 1936. Recent progress in the study of bird-migration: a - review of the literature, 1926-35. Ibis, 13th ser., - 6(3):472-530, July 1. - -TICEHURST, C. B. - - 1916. Notes on migrants and moult, with special reference to - the moults of some of our summer visitants. Scottish - Naturalist, no. 50, pp. 29-38, February. - -TORDOFF, H. B. - - 1952. Notes on plumages, molts, and age variation of the Red - Crossbill. Condor, 54(4):200-203, July-August. - -WIEGOLD, H. - - 1926. Masse, Gewichte und Zug nach Alter und Geschlecht bei - Helgoländer Zugvögeln. Wissenschaftliche - Meeresuntersuchungen, Abt. Helgoland, Neue Folge, 15ter - Band, Heft 3, No. 17, Lipsius & Tischer, Kiel und Leipzig, - pp. 1-73. - -WOLFSON, A. - - 1954. Weight and fat deposition in relation to spring - migration in transient White-throated Sparrows. Auk, - 71(4):413-434. - -_Transmitted June 30, 1955._ - - - - -Transcriber's Notes: - - -Words surrounded by _ are italicized. - -Small capitals are presented as all capitals in this e-text. - -Obvious printer's errors have been repaired, other inconsistent -spellings have been kept, for example inconsistent use of hyphen (e.g. -"age-classes" and "age classes") and diacritical mark (e.g. "Zool." -and "Zoöl."). - - - - - -End of the Project Gutenberg EBook of Studies of Birds Killed in Nocturnal -Migration, by Harrison B. Tordoff and Robert M. 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