8 



BULLETIN 185. U. S. DEPARTMENT OF AGRICULTURE. 



the rest remain stationary, as in the ease of the pine warbler and the 

 black-headed grosbeak, which do not venture in winter south of the 

 breeding range. With them fall migration is only a withdrawal from 

 the northern and a concentration in the southern part of the summer 

 home — the warbler in about a fourth and the grosbeak in less than an 

 eighth of the summer area. In the case of the Maryland yellow- 

 throat, the breeding birds of Florida are strictly nonniigratory, while 

 in spring and fall other yellow-throats pass through Florida in their 



Fig. 2. — Principal migration routes of North America. Most migrants use route No. 4, though this neces- 

 sitates a night of 500 to 700 miles across the Gulf of Mexico. A few traverse the more direct route No. 3, 

 and still fewer, route No. 2. Only water birds make the 2,400-mil9 flight along route No. 1, from Nova 

 Scotia to South America. (See p. 11.) 



journeys between their winter home in Cuba and their summer home 

 in New England. 



Another variation is illustrated by the robin, which occurs in the 

 middle districts of the United States throughout the year, in Canada 

 only in summer, and along the Gulf of Mexico only in winter. Prob- 

 ably no individual robin is a continuous resident in any section; but 

 the robin that nests, let us say, in southern Missouri, spends the winter 

 near the Gulf, while his hardy Canada-bred cousin is the winter tenant 

 of the abandoned summer home of the southern bird . 



Most migratory birds desert the entire region occupied in summer 

 for some other district adopted as a winter home. These two homes 



