142 WITH THE U. S. NATURALISTS 



Mexico to Colombia, although this means a direct 

 flight over the water of 500 to 700 miles." 



''I'd reckon," said Bull, after a moment's 

 thought, ''they'd go down by Palm Beach and the 

 keys to West Indies an' south that way." 



"That does look like a natural highway, sure 

 enough," answered the official, "but, as a matter 

 of fact, out of all our birds, there are only six 

 species that use it all the way." 



"Why is that?" asked Shan. 



"Lack of food," was the answer, "which, as I 

 said a little while ago, is a great factor in deter- 

 mining the currents of migration. The area of all 

 the West Indies, east of Porto Eico, is only a little 

 larger than the territory of the small state of 

 Rhode Island. So, if a large number of migrating 

 species used that route, stopping for food as they 

 went along, there wouldn't be enough for all of 

 them to eat. 



"Although the route from Florida to Cuba and 

 Jamaica requires single flights which are longer 

 than the highway of the outside islands, it is much 

 more popular. This is the Bobolink route, and, 

 Shan, your friend the Chuck-Will 's-Widow goes 

 that way. So does the Kingbird, one of the 

 Yireos, the two New England Cuckoos, the Gray- 



