DISTRIBUTION. 15 



Lawrence, thence almost due north for 2,000 miles to its breeding 

 grounds, but it is practically unknown in the interior of Canada. In 

 the fall many thousands migrate along the west shore of Hudson Bay 

 and from its southern borders cross to the Atlantic coast. Thus the 

 migration route is in the form of an ellipse some 3,000 miles long 

 north and south by 1,000 miles wide. 



Probably in no other region in the world do so large a proportion 

 of the birds migrate approximately north and south as in North 

 America north of the Gulf of Mexico. The outlines of the coast, the 

 courses of the large rivers, and the trend of the mountain chains unite 

 to make northward and southward migration easy and natural. In the 

 case of ducks, however, there is a factor that causes thousands of 

 individuals of several species to take a northwest-and-southeast route. 

 The Atlantic coast from Chesapeake Bay to South Carolina is especially 

 favorable as a winter home for ducks and until recent years countless 

 flocks swarmed throughout this district. Such other birds as winter in 

 this region breed principally in New England and northward along the 

 Atlantic slope to Labrador. But northeastern North America east of 

 Hudson Bay harbors only a small number of ducks in summer. 

 They prefer the marshes, lakes, and streams of the districts west of 

 Hudson Bay, and the great bulk of North American ducks breed there. 

 Thus there are two great districts, one suitable for a summer home 

 and the other for winter, and the migration route between them is 

 nearly northwest and southeast, between Chesapeake Bay and Great 

 Slave Lake. Through much of the intervening 2,000 miles is a suc- 

 cession of lakes, large and small, that find no counterpart elsewhere 

 on this hemisphere, and which furnish ideal conditions for ducks, 

 both as regards food and shelter. 



Among the most conspicuous species that follow this migration 

 route are the redhead, canvasback, and greater scaup. Less abun- 

 dant, though still numerous, are the baldpate, pintail, and lesser scaup, 

 while the route is extensively used also by the mallard, gadwall, 

 shoveler, and ring-necked duck. Nearly all the individuals of these 

 10 species that winter along the Atlantic coast reach their winter home 

 by a pronounced southeastward migration, though it must be under- 

 stood that these individuals constitute only a small percentage of the 

 vast army of these same species that breed in central Canada. 



One of the principal winter homes of North American ducks and 

 geese is the State of California, where congregates during this season 

 the larger part of all the individuals that breed west of the Eocky 

 Mountains. 



DISTRIBUTION. 



The family of ducks, geese, and swans is represented in North 

 America by 63 species and 8 subspecies — a total of 71 recognized 

 4510— No. 26—06 2 



