BIRDS OF NEW YORK 403 



is not hatched and the warbler's brood is saved from destruction. Although 

 I have noticed many of our native birds desert their nests when they have 

 been parasitized by the Cowbird, the Yellow warbler is the only one that 

 I have noticed which builds a new lining over the interloper's egg. 



The food of the Yellow warbler consists largely of smooth caterpillars, 

 plant lice, small beetles, various flies, especially the Ephemeridae and the 

 smaller Hymenoptera. During the migration season I have watched the 

 Yellow warbler in company with other species devouring plant lice in 

 apple trees and shade trees about our lawns, and, before the young have 

 left the nest, have noticed them bringing large numbers of measuring 

 worms and green caterpillars, gall flies and lake flies. Aside from the 

 destruction of a few beneficial beetles and parasitic Hymenoptera, this 

 beautiful little bird does no damage at all and in general it must be con- 

 sidered a very beneficial species, and it is at the same time one of the 

 most beautiful and interesting of those which nest about our gardens and 

 orchards. 



Dendroica caerulescens caerulescens (Gmelin) 



Black-throated Blue Warbler 



Plate 94 



Motacilla caerulescens Gmelin. Syst. Nat. 1 789. 1 : 960 



Sylvicola canadensis DeKav. Zool. N. Y. 1844. pt 2, p. 98, fig. iog and 



131 

 Dendroica caerulescens caerulescens A. O. U. Check List. Ed. 3 . 

 1910. p. 312. No. 654 



caerulescens , Lat., bluish, beginning to be blue 



Description. Adult male: Upper parts grayish blue; cheeks, throat and 

 sides black; lower breast and belly pure white; wings and tail blackish but 

 edged and overlaid with the color of the back so that when closed the whole 

 upper parts seem nearly uniform in color; a conspicuous white spot in 

 the wing formed by the white bases of the primaries; the 3 outer tail 

 feathers with conspicuotts white spots on their inner webs. Adult female: 

 An inconspicuous, neutral colored warbler; upper parts dusky olive green 

 with only a tinge of bluish on the crown and tail; an obscure whitish line 

 over the eye; dingy white spot in the wing at the base of the primaries in 

 the same position as the pure white spot in the male's wing; under parts 

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