nest in the higher mountains, move down to the lower regions in 

 August following the breeding season. There is a distinct tendency 

 among the young of mountain-breeding birds to work down to the 

 lower levels as soon as the nesting season is over. The sudden in- 

 creases among birds in the edges of the foothills are particularly notice- 

 able when cold spells with snow or frost occur at the higher altitudes. 

 Some species that normally breed in the Hudsonian or Arctic Zones 

 find suitable breeding areas on the higher levels of the mountains, as for 

 example the pipit, or titlark, which breeds on the tundra of Alaska and 

 northern Canada and also south as far as Colorado on the summits of 

 many peaks in the Rocky Mountains. On the other hand, a few 

 species, as the Clark's crow, or nutcracker, nest at relatively low alti- 

 tudes in the mountains and as the summer advances move higher up, 

 thus performing a vertical migration that in a sense is comparable with 

 the post-breeding movements of herons on the Atlantic coast. These 

 illustrations show that the length of a migration route may depend 

 upon factors other than latitude. 



Vagrant Migration 



The most striking feature of the migrations of some of the herons 

 is a northward movement after the nesting season. The young of 

 some species commonly wander late in the summer and in fall, some- 

 times traveling several hundred miles north of the district in which 

 they were hatched. The little blue heron breeds commonly north 

 to South Carolina, and by the last of July the young birds begin to 

 appear along the Potomac, Patuxent, and Susquehanna Rivers, tribu- 

 tary to Chesapeake Bay. Although almost all are immature individ- 

 uals, as shown by their white plumage, an occasional adult may be 

 noted. With them come egrets and snowy herons and on occasion 

 all three species will travel in the East as far north as New England, 

 and in the Mississippi Valley to southeastern Kansas and Illinois. In 

 September most of them disappear, probably returning south by the 

 same route. 



The black-crowned night heron has similar wandering habits, and 

 young birds banded in a large colony at Barnstable, Mass., have been 

 recaptured the same season north to Maine and Quebec and west to 

 New York. This habit seems to be shared by some of the gulls also, 

 although here the evidence is not so conclusive. Herring gulls banded 



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