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 AN AMERICAN'S VIEWS OF BIRD MIGRATION.* 



BY 

 J. A. ALLEN. 



Some birds are resident the whole year throughout the 

 areas they inhabit, while others move more or less north- 

 ward or southward with the change of the seasons, while 

 still others roam practically from pole to pole. The 

 extent of the seasonal movement varies in different 

 species mainly in accordance with the nature of their 

 food, and is also more or less correlated with their powers 

 of flight, the greatest wanderers being also strong of wing. 

 Most of the Grouse tribe and many of the hardy, seed- 

 eating, semi-omnivorous Passerine birds, are nearly or 

 quite non-migratory, while such exclusively insectivorous 

 and berry-eating species as Swallows, Flycatchers, 

 Warblers, and many of the Shore-birds make semi-annual 

 journeys of thousands of miles. Again, many birds 

 that are resident as species over large areas are, in winter, 

 more or less nomadic as individuals ; in other species 

 the more northern representatives move to a small ex- 

 tent north or south with the change of seasons. In the 

 species of this latter class the individuals that breed in 

 the southern part of the common range of the species are 

 permanently resident throughout the year, while those 

 that breed in the northern part move to lower latitudes 

 at the approach of winter, returning to their breeding 

 stations with the return of summer. Other species entirely 

 leave their breeding ranges in winter, migrating often 

 thousands of miles to reach their winter quarters. There 

 is thus every degree of migratory movement in different 

 species of birds, from slight nomadic movements to ex- 

 tended migration, in accordance with the physiological 

 needs of the species. 



* The present article, written by request, is a brief statement of the 

 author's present views on the subject of Bird Migration, to which he 

 has for many years given careful consideration. To go into a discus- 

 sion of the whys and wherefores would require the space of a volume. 

 It has therefore seemed sufficient to give here his conclusions, with 

 merely a slight thread of argument and evidence. — J. A. A. 



