JAX., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 



649 



Adult female: Similar, but upper 

 parts slightly deeper olive yellow than 

 the male; under parts, pale yellow, 

 rufous streaks faint or entirely wanting. 

 Diagnostic character in any plumage: 

 Tail feathers, fuscous brown, with inner 

 webs largely clear yellow. 

 Length, 4.90; wing, 2.50; tail, 2; bill, .38. 



The Yellow Warbler is a very common summer resident in Illinois 

 and Wisconsin; noticeable on account of its yellow plumage. The 

 majority arrive from the south the latter part of April or early in 

 May, and leave early in September. Aside from its familiar chirp 

 it has a pleasing song, which may be crudely described as we-chee, 

 we-chee, we-chee-u. 



Breeds in May and June; the nest is cup shaped, usually in bushes 

 or low trees, and composed of plant fiber and grass, lined with plant 

 down and feathers. The eggs are from 3 to 6, bluish or greenish 

 white, spotted with light and very dark brown and gray chiefly at 

 the larger end, and measure about .68 x. .49 inches. 



The Field Museum collection contains a series of sets of eggs of 

 this species taken in northern Illinois between June 8th and i8th. 



312. Dendroica caerulescens (GMEL.). 

 BLACK-THROATED BLUE WARBLER. 



Distr.: Eastern North America, west to the Rocky Mountains 

 and north to Labrador, northern Ontario, and Quebec; breeds from 

 northern New England and northern New York northward and in 

 the Alleghany Mountains south to Georgia; winters in the West 

 Indies, Central America, and northern South America. 



Adult male: Upper plumage, slaty 

 blue (occasionally in full breeding 

 plumage showing more or less black on 

 the back) ; sides of the head from above 

 the eyes, throat and sides of body, 

 black, the sides more or less mixed with 

 white ; rest of under parts, pure white ; 

 basal portion of most of quills, white, 

 extending beyond the coverts and form- 

 ing a white wing spot ; wing coverts, black, edged with slaty blue ; 

 tail, blackish, the outer feathers with white blotches on inner webs. 



