The several important bird-protective measures adopted by State and Federal Governments, particularly those having as their objective the conservation of the migratory song, insectivorous, and game species, can be effective only if they have intelligent public support. To increase such support, information must be more generally available on that little understood but universally fascinating subject of bird migration. A brief presentation of facts on the migratory habits of the birds, scientifically gathered by the Bureau of Biological Survey over many years, will be helpful to bird-study classes, to conservation organizations, and to farmers and others individually interested in the welfare of the birds. =THE MYSTERY OF MIGRATION= HISTORICAL ACCOUNTS Of observers whose writings are extant, Aristotle, naturalist and philosopher of ancient Greece, was one of the first to discuss the subject of bird migration. He noted that cranes traveled from the steppes of Scythia to the marshes at the headwaters of the Nile, and that pelicans, geese, swans, rails, doves, and many other birds likewise passed to warmer regions to spend the winter. In the earliest years of the Christian era, the elder Pliny, Roman naturalist, in his Historia Naturalis, repeated much of what Aristotle had said on migration, and added comments of his own concerning the movements of the European blackbird, the starling, and the thrushes. In spite of the keen perception shown in some of his statements, Aristotle also sponsored some superstitions on bird migration that persisted for several centuries. One of these, that of hibernation, became so firmly rooted that in 1878, the American ornithologist Coues (_20_)[2] listed the titles of no less than 182 papers dealing with the hibernation of swallows (Hirundinidae). The hibernation theory accounted for the autumnal disappearance of certain species of birds as their passing the cold season in a torpid state, hidden in hollow trees, caves, or 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 flocks of swallows seen congregating in the marshes until their accumulated weight bent into the water the reeds on which they clung and thus submerged the birds. It was even recorded that when fishermen in northern waters drew up their nets they sometimes had a mixed "catch" purported to consist of fish and hibernating swallows. Clarke (_4_) quotes Olaus Magnus, Archbishop of Upsala, who in 1555 published a work entitled "Historia de Gentibus Septentrionalibus et Natura", wherein he observed that if swallows so caught were taken into a warm room they soon begin to fly about but would live only a short time. [Footnote 2: Ttalic numbers in parentheses refer to the Bibliography, p. 66.]