BIED MIGRATION. 13 



longer than the water route. Yet beyond Cuba this highway is httle 

 used. About 25 species contmue as far as Porto Rico and remain 

 there through the winter. Only adventurers of some six species 

 gain the South American mainland by completing the island chain. 

 The reason is not far to seek — scarcity of food. The total area of 

 all the West Indies east of Porto Rico is a little less than that of 

 Rhode Island. Should a small proportion only of the feathered 

 inhabitants of the Eastern States select this route, not even the 

 luxuriant fauna and flora of the Tropics could supply their needs. 

 A still more direct route, but one requiring longer single flights, 

 stretches from Florida to South America via Cuba and Jamaica (see 

 fig. 2, route 3). The 150 miles between Florida and Cuba are crossed 

 by tens of thousands of birds of some 60 different species. About 

 half the species take the next flight of 90 miles to the Jamaican 

 mountains. Here a 500-mile stretch of islandless ocean confronts 

 them, and scarcely a third of their number leave the forest-clad hOls for 

 the unseen beyond. Chief among these is the bobolmk (PL I), which, 

 now well fattened on fall seeds, is so fuU of strength and energy that 

 the 500-mile fhght to South America on the way to the waving pam- 

 pas of southern Brazil seems a trifle. Indeed, many bobolmks 

 appear to scorn the Jamaican resting point and to compass in a 

 single flight the 700 miles from Cuba to South America. With the 

 bobolink is an incongruous company of traveling companions — a 

 vireo, a kingbird, and a nighthawk that sunnner in Florida; the 

 chuck-will's-widow of the Gulf States; the two New England cuckoos; 

 the gray-cheeked' thrush from Quebec; the bank swallow from Labra- 

 dor; and the black-poU warbler from far-ofl" Alaska. But the 

 bobolinks so far outnumber all the rest that the passage across the 

 Caribbean from Cuba to South America may with propriety be called 

 the " bobohnk route." Occasionally a wood thrush or a tanager joins 

 the assemblage, but the "bobohnk route" as a whole is not popular 

 with other bhds, and , though many traverse it, they are but a fraction 

 of the multitudes of Nortli American birds that spend the winter in 

 the southern continent. 



GULF ROUTES. 



The main-traveled highway is that which stretches from north- 

 western Florida across the GuK, continuing the southwesterly 

 direction which most of the l)irds of the Atlantic coast follow in 

 journeying to Flori<la(soe fig. 2, route 4). A larger or smaller per- 

 centage of nearly all the species bound for South America take this 

 roiiruluboiit course!, quite regardless of the several-hundred-mUe flight 

 over tlio Gulf of !M(!xic,o, 



The hiifls ca.<^t of the Allegheny Mountains move southwest in tlie 

 full, approximately pumllcl wKli i]w. seacoust, and upparenMy keep 



