Throughout the ages, migratory birds have been important as a source of food after a lean winter and as the harbinger of a change in season. The arrival of certain species has been heralded with appropriate ceremonies in many lands; among the Eskimos and other tribes, the phenomenon to this day is the accepted sign of the imminence of spring, of warmer weather, and a change from winter food shortages. The pioneer fur traders in Alaska and Canada offered rewards to the Indian or Eskimo who saw the first flight of geese in the spring, and all joined in jubilant welcome to the newcomers.
As the North American Continent became more thickly settled, the large flocks of ducks and geese, rails, doves, and woodcock that always had been hunted for food became objects of the enthusiastic attention of an increasing army of sportsmen. Most of the nongame species were found to be valuable also as allies of the farmer in his never-ending warfare against insect pests. All species have been of ever-increasing recreational and esthetic value for untold numbers of people who enjoy watching birds. We began to realize our migratory bird resource was an international legacy (that cannot be managed alone by one state or country) and all nations were responsible for its well-being. The need for laws protecting game and nongame birds, as well as the necessity to regulate the hunting of diminishing game species, followed as a natural course. In the management of this wildlife resource, it has become obvious that continuous studies must be made of the species' habits, environmental needs, and travels. In the United States, the Department of the Interior recognizes the value of this resource and is devoted to programs that will ensure its preservation and wise use. Hence bird investigations are made by the U.S. Fish and Wildlife Service, an arm of the Interior Department, charged by Congress under the Migratory Bird Treaty Act, with the duty of protecting those species that in their yearly journeys, pass back and forth between the United States and other countries.
For more than three-quarters of a century the Fish and Wildlife Service and its predecessor, the Biological Survey, have been collecting data on the important details of bird migration. Scientists have gathered information concerning the distribution and seasonal movements of many species throughout the New World, from the Canadian archipelago south to the Argentine pampas. Supplementing these investigations is the work of hundreds of U.S. and Canadian university personnel and volunteer birdwatchers, who report on the migrations and status of birds as observed in their respective localities; while others place numbered bands on the legs of birds to determine their movements from one place to another. These data, stored in field notes, computer cards, scientific journals, and on magnetic tape constitute an enormous reservoir of information pertaining to the distribution and movements of North American birds. It is the purpose of this publication to summarize these data and present the more important facts about that little understood but universally fascinating subject of bird migration. The U.S. Fish and Wildlife Service is grateful to the many persons who have contributed their knowledge so that other people, be they bird study classes, conservation organizations, or just individuals interested in the welfare of the birds, may understand and enjoy this precious resource as well as preserve it for generations to come.
THE HISTORY AND SCOPE OF MIGRATION
The migrations of birds were probably among the first natural phenomena to attract the attention and arouse the imagination of man. Recorded observations on the subject date back nearly 3,000 years, to the times of Hesiod, Homer, Herodotus, Aristotle, and others. In the Bible there are several references to the periodic movements of birds, as in the Book of Job (39:26), where the inquiry is made: "Doth the hawk fly by Thy wisdom and stretch her wings toward the south?" The author of Jeremiah (8:7) wrote: "The stork in the heavens knoweth her appointed time; and the turtledove, and the crane, and the swallow, observe the time of their coming." The flight of quail that saved the Israelites from starvation in their wanderings through the Sinai wilderness is now recognized as a vast migration between their breeding grounds in eastern Europe and western Asia and their winter home in Africa.
Of observers whose writings are extant, Aristotle, naturalist and philosopher of ancient Greece, was one of the first to discuss the subject of bird migration. He noted cranes traveled from the steppes of Scythia to the marshes at the headwaters of the Nile, and pelicans, geese, swans, rails, doves, and many other birds likewise passed to warmer regions to spend the winter. In the earliest years of the Christian era, Pliny the Elder, Roman naturalist, in his "Historia Naturalis," repeated much of what Aristotle had said on migration and added comments of his own concerning the movements of starlings, thrushes, and European blackbirds.
Aristotle also must be credited with the origin of some superstitious beliefs that persisted for several centuries. One of these, that birds hibernated, became so firmly rooted, Dr. Elliott Coues (1878),[1] an eminent American ornithologist, listed the titles of no less than 182 papers dealing with the hibernation of swallows. In fact the hibernation theory survived for more than 2,000 years, and it was not until early in the nineteenth century that its acceptance as an explanation for the winter disappearance of birds was almost completely abandoned. Even after this, a few credulous persons suggested this idea as an explanation for the disappearance of chimney swifts in the fall before bands from wintering swifts were finally reported as taken by Indians in Peru (Coffey 1944).
[1] Publications referred to parenthetically by date are listed in the [Bibliography, p. 102].
The followers of Aristotle believed the disappearance of many species of birds in the fall was accounted for by their passing into a torpid state where they remained during the cold season, hidden in hollow trees, caves, or in the mud of marshes. Aristotle ascribed hibernation not only to swallows, but also to storks, kites, doves, and others. Some early naturalists wrote fantastic accounts of the flocks of swallows allegedly seen congregating in marshes until their accumulated weight bent into the water the reeds on which they clung and thus submerged the birds. It was even recorded that when fishermen in northern waters drew up their nets they sometimes had a mixed "catch" of fish and hibernating swallows. Clarke (1912) quotes Olaus Magnus, Archbishop of Upsala, who in 1555 published a work entitled "Historia de Gentibus Septentrionalis et Natura," wherein he observed that if swallows so caught were taken into a warm room they would soon begin to fly about but would live only a short time.
Although the idea of hibernation as a regular method of spending the winter is no longer accepted for any species of bird, certain hummingbirds, swifts, and poorwills have been known to go into an extremely torpid condition in cold weather (Jaeger 1948, 1949). Thus Aristotle was at least partially vindicated.