DI8TBIB1 TloN. 15 
Lawrence, thence almost due aorth for 2,000 mile- to it- breeding 
grounds, but it is practically unknown in the ulterior of Canada. In 
the fall many thousands migrate along the wesl 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 <*». 000 miles long 
north and south by L,000 miles wide. 
Probably in do 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-southeasl route 
The Atlantic coasi from Chesapeake Bay to South Carolina is especially 
favorable as a winter home for ducks and until recent years countless 
flocks ^warmed throughout this district. Such other birds as winter in 
this region breed principally in New England and northward along tUe 
Atlantic slope to Labrador. But northeastern North America easl 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, gad wall, 
shoveler, and ring-necked duck. Nearly all the individuals of these 
In 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 Rocky 
Mountains. 
DISTRIBUTION. 
The family of ducks, geese, and swans is represented in North 
America by 63 species and 8 subspecies — a total of 71 recognised 
4510— No. 20—06 2 
