Differing routes to various parts of a large breeding or wintering ground, and used by large groups of individuals of other species, are not unknown. For example, the redhead duck is one of the common breeding ducks of the Bear River marshes of Utah, where a great many have been banded each summer. The recovery records of banded redheads show that while many travel westward to California, others start their fall migration in the opposite direction and, flying eastward across the Rocky Mountains, either turn southeast across the plains to the Gulf of Mexico, or deliberately proceed in a northeasterly direction to join the flocks of this species moving toward the Atlantic coast from the prairie regions of southern Canada.
Conclusions
The migration of birds as it is known today had its beginning in times so remote that its origins have been entirely obscured, and it can be interpreted now only in terms of present conditions. The causes underlying migration are exceedingly complex. The mystery that formerly cloaked the periodic travels of birds, however, has been largely dispelled through the fairly complete information that is now available concerning the extent and times of the seasonal journeys of most of the species. Many gaps, however, still remain in our knowledge of the subject. Much has been learned, and present knowledge is being placed on record, but it must be left to future study to clear away many of the uncertainties that continue to make bird migration one of the most fascinating subjects in the science of ornithology.
Each kind of bird seems to have its own reaction to its environment, so that the character of movement differs widely in the various species, and seldom do any two present the same picture. In fact, bird migration has been described as a phase of geographic distribution wherein there is a more or less regular seasonal shifting of the avian population caused by the same factors that determine the ranges of the sedentary species. If this view is correct, then it must be recognized that the far-reaching works of man in altering the natural condition of the earth's surface can so change the environment necessary for the well-being of the birds as to bring about changes in their yearly travels. The nature and extent of the changes wrought by man on the North American Continent are easily apparent. Forests have been extensively cut away and their places have been taken by second growth or cultivated land, and wide stretches of prairie and plain have been broken up, irrigated, and devoted to agriculture. These great changes are exerting a profound effect upon the native bird populations, and the various species may be either benefited or adversely affected thereby.
The Federal Government has recognized its responsibility to the migratory birds under changing conditions brought about by man, and by enabling acts for carrying out treaty obligations, it is now giving most species legal protection under regulations administered by the Fish and Wildlife Service. Much is being done by legislation for the welfare of the birds. The effectiveness of these conservation laws, however, is increased in the same measure that the people of the country become acquainted with the facts in the life histories of the migrants and interest themselves personally in the well-being of the various species. Long before the white man came to America the birds had established their seasonal lanes of migration throughout the Western Hemisphere. The economic, inspirational, and esthetic values of these migratory species dictate that they be permitted to continue their long-accustomed and still-mysterious habits of migration from clime to clime.
Appendix I—List of Birds Mentioned in the Text
| Common name | Scientific name |
| American egret | Casmerodius albus egretta |
| Arctic tern | Sterna paradisaea |
| Atlantic brant | Branta bernicla hrota |
| Atlantic golden plover | Pluvialis dominica dominica |
| Bank swallow | Riparia riparia |
| Barn swallow | Hirundo rustica erythrogaster |
| Bartramian sandpiper or upland plover | Bartramia longicauda |
| Belted kingfisher | Ceryle alcyon |
| Black-and-white warbler | Mniotilta varia |
| Black-billed cuckoo | Coccyzus erythropthalmus |
| Black brant | Branta bernicla nigricans |
| Black-capped chickadee | Parus atricapillus atricapillus |
| Black-crowned night heron | Nycticorax nycticorax hoactli |
| Black duck | Anas rubripes |
| Black-headed grosbeak | Pheucticus melanocephalus |
| Blackpolled warbler | Dendroica striata |
| Black-throated blue warbler | Dendroica caerulescens |
| Bluebird | Sialia sialis |
| Blue goose | Chen caerulescens |
| Blue jay | Cyanocitta cristata |
| Bluethroat | Cyanosylvia suecica |
| Blue-winged teal | Anas discors |
| Bobolink | Dolichonyx orizivorus |
| Bobwhite | Colinus virginianus |
| Bohemian [greater] waxwing | Bombycilla garrulus pallidiceps |
| Brewer's blackbird | Euphagus cyanocephalus |
| Broad-winged hawk | Bueto platypterus |
| Bronzed grackle | Quiscalus guiscula versicolor |
| Brown [tree] creeper | Certhia familiaris |
| Cackling [Canada] goose | Branta canadensis minima |
| California quail | Lophortyx californica |
| Canada goose | Branta canadensis |
| Canvasback | Aythya valisineria |
| Cape May warbler | Dendroica tigrina |
| Cardinal | Richmondena cardinalis |
| Carolina chickadee | Parus carolinensis |
| Carolina wren | Thryothorus ludovicianus |
| Chimney swift | Chaetura pelagica |
| Chipping sparrow | Spizella passerina |
| Chuck-wills-widow | Caprimulgus carolinensis |
| Clark's nutcracker | Nucifraga columbiana |
| Cliff swallow | Petrochelidon pyrrhonota |
| Common tern | Sterna hirundo |
| Cooper's hawk | Accipiter cooperi |
| Coot [American] | Fulica americana |
| Cowbird | Molothrus ater |
| Crossbill | Loxia curvirostra |
| Crow | Corvus brachyrhynchos |
| Duck hawk [peregrine falcon] | Falco peregrinus |
| Eastern fox sparrow | Passerella iliaca iliaca |
| Eider | Somateria mollissima |
| Emperor goose | Philacte canagica |
| Evening grosbeak | Hesperiphona vespertina |
| European blackbird | Turdus merula merula |
| Field sparrow | Spizella pusilla |
| Forster's tern | Sterna forsteri |
| Frigate [man-o'-war] bird | Fregata magnificens |
| Golden-crowned kinglet | Regulus satrapa |
| Golden plover | Pluvialis apricaria |
| Golden-winged warbler | Vermivora chrysoptera |
| Goshawk | Accipiter gentilis |
| Grackle | Quiscalus quiscula |
| Gray-cheeked thrush | Hylocichla minima |
| Greenland wheatear | Oenanthe oenanthe leucorhoa |
| Harris's sparrow | Zonotrichia querula |
| Hermit thrush | Hylocichla guttata |
| Herring gull | Larus argentatus |
| Horned lark | Eremophila alpestris |
| Horned owl | Bubo virginianus |
| House finch | Carpodacus mexicanus |
| Ipswich sparrow | Passerculus princeps |
| Jacksnipe [see Wilson's snipe] | Capella gallinago delicata |
| Junco | Junco hyemalis |
| Kentucky warbler | Oporonis formosus |
| Kingbird | Tyrannus tyrannus |
| Knot | Calidris canutus |
| Kodiak fox sparrow | Passerella iliaca hyperborea |
| Lapland longspur | Calcarius lapponicus |
| Lapwing | Vanellus vanellus |
| Lesser yellowlegs | Totanus flavipes |
| Little blue heron | Florida caerulea |
| Loggerhead shrike | Lanius ludovicianus |
| Long-billed marsh wren | Telmatodytes palustris |
| Mallard | Anas platyrhynchos |
| Maryland yellowthroat | Geothlypis trichas trichas |
| Meadowlark | Sturnella magna |
| Migratory quail | Coturnix coturnix |
| Mockingbird | Mimus polyglottos |
| Mourning dove | Zenaidura macroura |
| Myrtle warbler | Dendroica coronata |
| Nighthawk | Chordeilies minor |
| Noddy tern | Amous stolidus |
| Northern phalarope | Lobipes lobatus |
| Northern robin | Turdus migratorius migratorius |
| Orchard oriole | Icterus spurius |
| Ovenbird | Seiurus aurocapillus |
| Pacific [American] golden plover | Pluvialis dominica fulva |
| Parasitic jaeger | Stercorarius parasiticus |
| Peregrine falcon [duck hawk] | Falco peregrinus |
| Pine Grosbeak | Pinicola enucleator |
| Pine warbler | Dendroica pinus |
| Pintail | Anas acuta tzitzihoa |
| Pipit | Anthus spinoletta |
| Poor-will | Phalaenoptilus nuttallii |
| Purple finch | Carpodacus purpureus |
| Purple martin | Progne subis |
| Purple sandpiper | Erolia maritima |
| Raven | Corvus corax |
| Red-eyed vireo | Vireo olivaceus |
| Redhead | Aythya americana |
| Red-legged kittiwake | Rissa brevirostris |
| Redpoll | Acanthis flammea |
| Redstart | Setophaga ruticilla |
| Red-tailed hawk | Buteo jamaicensis |
| Red-winged blackbird | Agelaius phoeniceus |
| Robin | Turdus migratorius |
| Rock wren | Salpinctes obsoletus |
| Rose-breasted grosbeak | Pheucticus ludovicianus |
| Ross's goose | Chen rossi |
| Ross's gull | Rhodostethia rosea |
| Rosy finch | Leucosticte tephrocotis |
| Rough-legged hawk | Buteo lagopus |
| Ruby-throated hummingbird | Archilochus colubris |
| Ruffed grouse | Bonasa umbellus |
| Rusty blackbird | Euphagus carolinus |
| Sanderling | Crocethia alba |
| Scarlet tanager | Piranga olivacea |
| Scaup | Aythya marila |
| Screech owl | Otus asio |
| Sharp-shinned hawk | Accipiter striatus |
| Shumagin fox sparrow | Passerella iliaca unalaschensis |
| Slate-colored junco | Junco hyemalis |
| Snow bunting | Plectrophenax nivalis |
| Snow goose | Chen hyperborea |
| Snowy heron | Leucophoyx thula |
| Snowy owl | Nyctea scandiaca |
| Song sparrow | Melospiza melodia |
| Sooty fox sparrow | Passerella iliaca fuliginosa |
| Sooty tern | Sterna fuscata |
| Sora or Carolina rail | Porzana Carolina |
| Southern robin | Turdus migratorius achrusterus |
| Starling | Sturnus vulgaris |
| Swainson's hawk | Buteo swainsoni |
| Swamp sparrow | Melospiza georgiana |
| Townsend's fox sparrow | Passerella iliaca townsendi |
| Tree sparrow | Spizella arborea |
| Tufted titmouse | Parus bicolor |
| Turkey vulture | Cathartes aura |
| Turnstone | Arenaria interpres |
| Upland plover [Bartramian sandpiper] | Bartramia longicauda |
| Valdez fox sparrow | Passerella iliaca sinuosa |
| Vesper sparrow | Pooecetes gramineus |
| Western palm warbler | Dendroica palmarum palmarum |
| Western tanager | Piranga ludoviciana |
| Western wood pewee | Contopus richardsonii |
| White-breasted nuthatch | Sitta carolinensis |
| White-throated sparrow | Zonotrichia albicollis |
| White-winged scoter | Melanitta fusca |
| Widgeon | Mareca americana |
| Williamson's sapsucker | Sphyrapicus thyroideus |
| Wilson's [common] snipe | Capella gallinago delicata |
| Winter wren | Troglodytes troglodytes |
| Woodcock | Scolopax rusticola |
| Wood thrush | Hylocichla mustelina |
| Worm-eating warbler | Helmitheros vermivorus |
| Wrentit | Chamaea fasciata |
| Yakutat fox sparrow | Passerella iliaca annectens |
| Yellow-billed cuckoo | Coccyzus americanus |
| Yellow-billed loon | Gavia adamsii |
| Yellow-headed blackbird | Xanthocephalus xanthocephalus |
| Yellow palm warbler | Dendroica palmarum hypochrysea |
| Yellow warbler | Dendroica petechia |
Appendix II—Bird Banding
Frequent reference has been made in this bulletin to bird banding as a means for obtaining information on the migrations and life histories of birds. Since 1920 this work in North America has been under the direction of the Fish and Wildlife Service in cooperation with the Dominion Wildlife Service of Canada. Each year birds to the number of a quarter of a million or more may be marked with numbered bands.
As anyone interested in birds, either game or nongame, may have a marked individual come into his hands, there are several pertinent details that should be remembered if the recovery record is to have maximum value in advancing the science of ornithology.