BIRD MIGRATION ix 



Nor are they content with journeying to northern South America, but many cross the 

 Equator and pass on to the pampas of Argentina and a few even to Patagonia. Among 

 these long-distance migrants are some of our commonest birds; the Scarlet Tanager migrates 

 from Canada to Peru; the Bobolinks that nest in New England probably winter in Brazil, 

 as do Purple Martins, Cliff Sparrows, Barn Sparrows, Nighthawks, and some Thrushes, 

 which are their companions both summer and winter. The Black-poll Warblers that nest 

 in Alaska winter in northern South America, at least 5,000 miles from the summer home. 

 The land bird with the longest migration route is probably the Nighthawk, which occurs 

 north to Yukon and south 7,000 miles away, to Argentina. 



But even these distances are surpassed by some of the water birds, and notably by some 

 of the shorebirds, which as a group have the longest migration routes of any birds. Nine- 

 teen species of shorebirds breed north of the Arctic Circle, every one of which visits South 

 America in winter, six of them penetrating to Patagonia, a migration route more than 8,000 

 miles in length. The world's migration champion, however, is the Arctic Tern. 



The shape of the land areas in the northern half of the Western Hemisphere and the 

 nature of the surface has tended to great variations in migratory movements. If the whole 

 area from Brazil to Canada were a plain with the general characteristics of the middle section 

 of the Mississippi Valley, the study of bird migration would lose much of its fascination. 

 There would be a simple rhythmical swinging of the migration pendulum back and forth, 

 spring and fall. But much of the earth's surface between Brazil and Canada is occupied by 

 the Gulf of Mexico, the Caribbean Sea, and parts of the Atlantic Ocean, all devoid of 



Most migrants use n 

 traverse the mo 

 along route No. 



l^jurtL-sy of U. S. Uept. of Agriculture 



PRINCIPAL MIGRATION ROUTES OF NORTH AMERICA 



ute No. 4. though this necessitates a flight of 500 to 700 miles across the Gulf of Mexico. A few 

 re direct route No. ,i, and still fewer, route No. 2. Only water birds make the 2,400-nule flight 

 I, from Nova Scotia to South America. 



