Loomis, Birds, Chester Co. S.O, 
5 6. Vireo solitarius. Blue-headed Vireo.— The Blue-headed Vireo is 
a regular, but not common migrant. In spring it occurs in April (41021). 
In fall, it returns about the middle of October — 15th the earliest date — 
and abides until November. Laggards sometimes linger on into this 
latter month. These Vireos sing finely in April, and occasionally, though 
imperfectly, in autumn. While uttered with equal force and unction, the 
musical efforts of the vernal performers (intermediates) seem to lack the 
penetrating power peculiar to alticola as heard in its mountain home. 
Still they may not attain their complete song when migrating. 
All the spring specimens that have been taken are intermediate between 
solitarius and alticola (their upper parts beyond the rump being strongly 
washed with plumbeous), while the majority ol the autumnal ones aie 
typical solitarius. Taking the Pickens examples (Auk, Vol. VII, p. 126) 
as a basis of comparison, I am impelled to rank these intergrades with 
solitarius. The uniform deep black of the bill in adult alticola seems to 
be a more potent character in the discrimination of the two forms than the 
variable plumbeous veiling of the upper portions, which, however, in ex. 
treme alticola is always diagnostic. In Chester specimens— both in spring 
and fall— the lower mandible invariably displays plumbeous. In some the 
plumbeous predominates, the tip only being black. The black of the 
whole bill is of a slaty cast, not an intense black as in the mountain race. 
Mr. Ridgway has informed me that the examples of solitarius which have 
passed under his notice have invariably had the basal half, at least, of the 
lower mandible plumbeous. 
Attk, 3, April,139L p* lb? 
