Cir 
est 
THE MIGRATION OF NORTH AMERICAN BIRDS 
straight as to attain these small oceanic islands, 2,000 miles south 
of the Aleutians, 2,000 miles west of Baja California, and nearly 
4,000 miles east of Japan, the evidence admits only the conclusion 
that year after year this transoceanic round-trip journey between 
Alaska and Hawaii is made by considerable numbers of golden plovers. 
B4499M 
FIGURE 26.—Migration of the western tanager. The birds that arrivein eastern Alberta by May 20 do not 
travel northward along the eastern base of the Rocky Mountains, as in that region the van has then only 
reached northern Colorado. Instead the isochronal lines indicate that they migrate north through 
California, Oregon, and Washington, and then cross the mountains of British Columbia. 
The Pacific oceanic route probably is used also by the arctic 
terns that breed in Alaska, and possibly by those from the more west- 
ern tern colonies of Canada. This species is of regular occurrence on 
the western coasts of both the United States and South America, 
indicating that the western representatives travel southward to the 
Antarctic winter quarters without the spectacular migration features 
