44 ROUTES OF MIGRATION 
Porto Rico from the westward. This route, however, is followed by 
only a small portion of the birds which migrate southward, through 
Florida and the Bahamas, into the Greater Antilles. If they continue 
their journey to South America, most of them do so through Jamaica, 
the 400 miles of water separating this island from northern South 
= 
Fie. 7. Migration of the Bobolink. A species which breeds west of the Rocky 
Mountains, but migrates through the southeastern United States, reaching South 
America through the Greater Antilles and Central America. 
eee area—Breeding range. Black area—Winter range. Arrows—Migration 
route, 
America being evidently no barrier to such great. travelers as the Bobo- 
link and Blackpoll Warbler. 
Within the limits of the United States, coast-lines, mountain 
chains, and the larger river valleys, appear to be followed by birds 
in their migrations; nevertheless, there is a more or less pronounced 
