296 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



a man near the young. An alarm call, used at such a time, is a protesting 

 "shu shu shu shu shu." Even this note is gentle when compared with the alann 

 notes of most birds. 



Young are fed by both birds, chiefly on insects, of which span-worms are the 

 most conspicuous and easily identified. One student observed a dragon fly fed 

 to the young, wings and all. From her description it was apparently Aeschna 

 umhrosa, a fairly large species. It is not probable that a vireo could catch 

 a fully matured adult dragon fly, but in the morning, when the insects have just 

 emerged from the nymph stage, their wings are soft and they are incapable of 

 flight, and easily caught. 



When the young are out of the nest, parents are still busy feeding them for 

 a few days. At such times, if the young are near the ground, the parents still 

 show little fear of man, and come to feed them in front of groups of people and 

 camera lenses. 



The very early and very late dates at which eggs have been found 

 suggest that two broods are sometimes raised in a season, as seems to 

 be the case with the mountain vireo. 



Plumages. — The ju venal plumage of the blue-headed vireo is much 

 like that of the adult in pattern, but the general coloration is duller. 

 Dr. Dwight (1900) describes it, in part, as "above, drab, tinged with 

 green, pileum and auriculars clrab-gray. * * * Below, pure white, 

 tinged on flanks and crissum with primrose-yellow. Obscure super- 

 ciliary stripe, loral and orbital regions white; a dusky anteorbital 

 streak." 



The first winter plumage is acquired by a partial postjuvenal molt 

 in August and September, which involves the contour plumage and 

 the wing coverts but not the rest of the wings nor the tail. In this 

 plumage the young bird is practically indistinguishable from the 

 adult, though the head and back are more or less tinged with brownish 

 and the white of the underparts is less pure. Both old and young 

 birds usually, though perhaps not always, have a partial and irregular 

 prenuptial molt in March and April, at which a few or more feathers 

 are renewed on the head, back, throat, and breast. 



The sexes are practically alike in all plumages, though the colora- 

 tion of the female is usually duller. 



Food. — The Biological Survey had 30G well-filled stomachs of the 

 blue-headed vireos and 28 other stomachs only partially filled, on 

 which Dr. Edward A. Chapin (1925) based his report on the food of 

 this species. The animal matter, 96.32 percent of the entire food, con- 

 sisted almost entirely of insects, the few spiders included amounting 

 to 2.63 percent and the snails 0.25 percent. Lepidoptera, in all stages, 

 were the largest items, averaging 38.8 percent for the whole year; 

 caterpillars were eaten in greatest numbers in March (41.56 percent) 

 and in Sejotember (40.39 percent) ; the greatest consumption of adult 

 moths came in July (18.38 percent). Hemiptera, true bugs, formed 

 the second largest item, averaging 20.13 percent for the year, stink 

 bugs (Pentatomidae) predominating. Dr. Chapin writes: 



