enormous ellipse with the minor axis about 2,000 miles and the major 

 axis 8,000 miles, reaching from the Arctic tundra to the pampas of 

 Argentina. The older birds are probably accompanied by some of 

 the young, perhaps those from early nestings, but most of the immature 

 birds leave their natal grounds late in summer and move southward 

 through the interior of the country, returning in spring over essen- 

 tially the same course. The elliptical route is therefore used chiefly by 

 fully adult birds. 



Atlantic coast route and tributaries 



The Atlantic coast is a regular avenue of travel, and along it are 

 many famous points for observing both land and water birds. About 

 50 different kinds of land birds that breed in New England follow the 



Figure 17. — Principal migration routes used by birds in passing from 

 North America to winter quarters in the West Indies, Central America, 

 and South America. Route No. 4 is the one used most extensively; 

 only a few species make the 2,400-mile flight from Nova Scotia to 

 South America. 



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