270 DwiGHT, The Philadelphia Vireo. [^^,y 



olivaceus, both of which are silky white below at the same age. 

 Other specimens in my series show the change of the young into 

 autumn plumage, which is acquired, as in Vireo olivaceus^ without 

 moult of flight-feathers or tail. These remain, although the body- 

 feathers begin to be replaced by new ones before the wings and 

 tail have attained their full growth. The feathers retained are 

 the primaries, their coverts, the secondaries, the tertiaries, and 

 the rectrices, — all the rest of the plumage is evanescent and is 

 renewed soon after the bird leaves the nest. A bird taken July 

 28 has the wings and tail fully grown but the deciduous sheaths 

 are still in place at the bases of the quills. The brown upper 

 parts are mottled with the bright olive-green autumn feathers 

 which have extensively replaced the others on the nape, back and 

 rump. The forehead and sides of head show many new feathers. 

 A yellow band below in strong contrast to the paler first plumage, 

 has developed on the throat and shows faintly on the flanks beyond 

 the forking of the inferior feather tract. The new wing-coverts 

 (except the primary coverts) are beginning to sprout. A bird 

 taken August 4 is farther advanced. The sheaths of the quill 

 feathers have disappeared ; the wing-coverts are nearly full 

 grown ; and the new body plumage is nearly complete, only a few 

 feathers still in their sheaths sprouting here and there. A bird of 

 August 6 is almost entirely in fall dress, and others of August 1 5 

 are still moulting a few auricular and abdominal feathers, while 

 one of September 24 shows no trace whatever of the moult and is 

 practically indistinguishable from the adult. Still, in average 

 specimens the yellow below is a little richer and extends further 

 over the abdomen and the bill is yellowish instead of blackish as 

 in the adult. 



Whether there is any spring moult in this species I am unable 

 to say for I have seen no specimens taken at a time when it might 

 be expected to occur, but the state of the plumage in spring birds 

 indicates that there is none. The fall plumage of young and old 

 is probably worn until the next annual moult, which begins towards 

 the end of July. In spring specimens the amount of yellow is 

 variable, although paler than in the fall, and the abrasion is not at 

 all marked, but this is to be expected in an arboreal species. A 

 specimen of July 22 is the earliest one that shows signs of moult. 



