258 BULLETIN 197, UNITED STATES NATIONAL MUSEUM 



At the age of five and a half days, though the nestlings had grown much 

 larger, their eyes did not appear to have opened, and they continued to 

 be almost naked. A narrow blackish tract had started along the anterior por- 

 tion of the median line of the back, adjacent to the neck; edge of wing was 

 thickly sprouted; and there was slight indication of sprouting on crown and 

 hind head, and in the caudal tract. Nothing on rump or posterior portion of 

 back. Under parts showed barely an indication of broad, extensive tracts 

 along the sides, these showing whitish rather than blackish. At this age one 

 of the nestlings demonstrated a lusty voice for so small a creature — a squeaking 

 noise. 



Plumages. — According to Eidgway (1904), the young Bell's vireo 

 in Juvenal plumage is much like the adult, "but pileum and hindneck 

 soft drab, back and scapulars dark drab, under parts nearly pure 

 white, with sides, flanks, and under tail-coverts tinged with sulphur 

 yellow, wing-bands more distinct, and tertials edged with yellowish 

 white or pale sulphur yellow." 



Apparently the molts are similar to those of other closely related 

 vireos, a partial post ju venal molt in July and August, no prenuptial 

 molt, and a complete postnuptial molt late in summer. 



Food. — Dr. Edward A. Chapin's (1925) report on the summer food 

 of the Bell vireos, was based on the examination of 52 stomachs, col- 

 lected from May to August, inclusive. "Nearly all (99.3 per cent) 

 of the food taken is of animal origin, such forms as bugs, beetles, 

 caterpillars, and grasshoppers predominating." Hemiptera (bugs) 

 make up 34.43 percent of the summer food. Of Orthoptera, the aver- 

 age percentage is 18.52. Dr. Chapin continues: 



No other species of vireo of which the food habits are known takes so large 

 a quantity of such bulky insects as grasshoppers, locusts, and the like. Though 

 the present species is one of the smallest in size, it includes in its diet for 

 July enough of the orthopteroids to make 34.88 per cent of that month's 

 food. * * * About one-fifth (20.63 per cent) of the subsistence of the Bell 

 vireos during the summer is made up of caterpillars, and of adult moths and 

 butterflies, and their eggs. As the last-named items are rarely found in a 

 stomach, the figures given refer mainly to the first two. * * * Beetles of 

 all kinds make up 15.26 per cent of the summer food of the Bell vireos. Lady- 

 bird beetles are taken in moderate numbers and form 2.19 per cent of the total 

 food. Weevils (G.OO per cent) and leaf beetles (3.98 per cent) accoimt for 

 most of the remainder of coleopterous food. * • * Hymeuopterans of all 

 sorts (bees, wasps, etc.) amount to 6.44 per cent of the total diet. * * * The 

 rest of the animal food of the Bell vireos is composed of a few miscellaneous 

 insects and spiders and a very few snails, spiders (2.71 per cent) being the 

 most important. * * * It is not until July that the Bell vireos feed on wild 

 fruits. At that time 1.57 per cent of the subsistence is of vegetable matter. 



In his summary, he remarks : "Grasshoppers, locusts, caterpillars, 

 and moths are frequently injurious to man's best interests, as also 

 are many of the hemipterans. The percentage of these insects in the 

 food of birds of this species is 73.58, nearly three-fourths of the total. 

 Of the remainder about half the beetles and hymeuopterans are in- 



