630 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



A complete postnuptial molt occurs in July, at which an adult 

 winter plumage is assumed that differs only slightly from the first 

 winter plumage. 



These remarks refer to the male. The plumages and molts of the 

 female are similar, but the black cap is wholly lacking in the first 

 winter plumage and more restricted afterward. 



Food. — No comprehensive study of the food of "Wilson's warbler has 

 appeared in the literature, and practically nothing has been published 

 in detail on the food of our eastern bird. Prof. Beal (1907) examined 

 the contents of 53 stomachs of one of the western races of the species 

 and found that 93 percent of the food was animal matter and only 7 

 percent of it vegetable. There is no reason to suppose that the eastern 

 race has not a somewhat similar diet. Moreover, since our Wilson's 

 warbler has been seen repeatedly foraging among the twigs and foliage 

 of trees and shrubs, presumably in search of insects and their eggs 

 and larvae, or darting out into the air to capture flying insects, it may 

 be safely regarded as primarily insectivorous and hence mainly a 

 beneficent species. 



Dr. Alexander F. Skutch (MS.), speaking of the bird in Central 

 America, says : "Among the peculiar foods of the Wilson's warblers 

 in their winter home are the little, white, beadlike protein corpuscles 

 which they daintly pluck from the furry cushions at the bases of the 

 long petioles of the Cecropia tree. These minute grains, the chief 

 nourishment of the Azteca ants that dwell in myriads in the hollow 

 stems of the tree, are also sought by a number of other small birds, 

 both resident and migratory." 



Mrs. Edith K. Frey tells me that she has seen Wilson's warblers and 

 several other species of wood warblers feeding on aphids in her shrub- 

 bery day after day until the pests were gone. 



Behavior. — Wilson's warbler is a bright spot to bird watchers at 

 the full tide of migration in May, and again in late summer, although 

 we meet the bird less frequently during its southerly retreat from 

 its breeding ground. It is a bright spot not solely because of brilliancy 

 of plumage, but rather because it appears as a lively personality, 

 standing out sharply as an individual among the quieter warblers. 

 It gives us the impression of extreme alertness as it flits about in 

 the trees and shrubbery, fluttering among the foliage, dashing into 

 the air to capture flying insects, restless, full of energy, symbolizing, 

 in spring, its characteristics by its brisk, vivid song. William Brew- 

 ster (1936) thus pictures the bird: 



Wilson's Blackcap is a most interesting little bird, very like the Canadian 

 Warbler in general behavior, but fussier and more animated. It feeds chiefly 

 among low bushes (especially willows) near water and is incessantly in motion. 

 It is much given to making short, abrupt upward flights to seize insects from the 

 under sides of the leaves. It jerks its tail upward every few seconds and also 



