THE MIGRATION OF NORTH AMERICAN BIRDS a 
that now contain well over 2,500,000 entries, easily the greatest 
existing accumulation of information pertaining to the distribution 
and movements of North American birds. Not only do the facts 
thus assembled form the basis of regulatory action for the protection 
of the birds, but they also make it possible to publish scientific 
accounts of the ranges and migrations of the different species. They 
furnish the basis of this publication. 
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 avail- 
able 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 end 
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 move- 
ments of the Kuropean 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)? 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 sub- 
merged 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. 
2 Italic numbers in parentheses refer to the Bibliography, p. 66. 
