434 Birds of Colorado 
primary obvious, longer than the coverts; iris brown, bill pale 
horn, legs dusky. Length 4:90; wing 2-90; tail 2-2; culmen .40; 
tarsus -75. 
The sexes are alike ; the young bird has the top of the head buffy, 
and buffy tips to some of the coverts. 
Distribution. Breeding in western North America from British 
Columbia and Athabasca south along the eastern border of the Rocky 
Mountains to New Mexico and Lower California ; further south in 
winter to Vera Cruz and Oaxaca in Mexico. 
In Colorado this species is the commonest of the Vireos, arriving 
from the south about the middle of May in El Paso co., and spreading 
up into the mountains, where it breeds up to about 10,000 feet. The 
earliest date for EH] Paso co. is May 15th among the Aiken collection, 
but Warren gives May 3rd for Baca co., and Henshaw the same date 
for Fort Garland. Other recorded localities are Loveland, May 12th, 
W. G. Smith (Cooke), Boulder co. (Minot), Limon (Aiken), and Pueblo 
(Beckham), in the plains and foothills; in the mountains, Estes 
Park (Kellogg), Graymont, 10,000 feet (Keyser), Breckenridge (Carter 
apud Cooke), Twin Lakes (Scott), South Park (Allen), Mesa co., 
common, breeding at 7,500 feet (Rockwell), San Juan co. (Drew) and 
La Plata co. (Gilman). 
Habits.—The Warbling Vireo frequents deciduous trees, 
especially cotton-woods and aspens, and also groves 
and. orchards about the dwelling-places of man. They 
are celebrated for the sweetness of their song, their notes 
being soft, low and musical; according to Keyser they 
sing even while sitting on the nest. They are of great 
service to man as insect destroyers, devouring large 
numbers of scale and other insects injurious to fruit 
and shade trees. 
The nest, like that of the Red-eyed, is suspended to 
the slender forks of twigs either of a cotton-wood or at 
great elevations of a quaking aspen; it is somewhat 
smoother and more compact in its make-up. The eggs, 
four to five in number, are white, sparingly spotted 
about the larger end with reddish to dark brown and 
lilac. They measure about “75 x ‘55. Fresh eggs 
may be looked for about July Ist. 
