THE MIGRATION OF NORTH AMERICAN BIRDS 39 
The routes indicated on the maps (figs. 20 and 21) must not be con- 
sidered as representing paths with clearly defined borders, but rather 
as convenient subdivisions of the one great flyway that covers prac- 
tically the entire width of the North American Continent and extends 
from the Arctic coast to South America. 
ATLANTIC OCEANIC ROUTE 
By reference to figure 20 it will be noted that route no. 1 is almost 
entirely oceanic, passing directly over the Atlantic Ocean from 
Labrador and Nova Scotia to the Lesser Antilles, and then through this 
B1032M 
FIGURE 20.—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. 4is the one used most extensively; only 
a few species make the 2,400-mile flight from Nova Scotia to South America. 
croup of small islands to the mainland of South America. It is not 
used by any of the smaller land birds, but is followed chiefly by thou- 
sands of water birds and by shore birds of several species, the adult 
golden plover being a notable example. Since it lies entirely over the 
sea, this route is definitely known only at its terminals and from 
occasional observations made on Bermuda and other islands in its 
course. Some of the shore birds that breed on the Arctic tundras of 
Mackenzie and in Alaska fly southeastward across Canada to the 
Atlantic coast and finally follow the oceanic route to the mainland of 
South America. The golden plover may accomplish the whole 2,400 
miles without pause or rest, in fair weather the flocks passing Ber- 
muda and sometimes even the islands of the Antilles without stopping. 
Although most birds make their migratory flights either by day or by 
