510 ANIMAL LIFE IN THE YOSEMITE 



During the spring and early summer months the Western Warbling 

 Vireo is, within its range, one of the principal contributors to the early 

 morning chorus of bird voices. At El Portal on May 31, 1915, one of us 

 rated it as fourth among the various contestants, being exceeded in loudness 

 by only the Western Tanager, Pacific Black-headed Grosbeak, and Western 

 House Wren. The song is a voluble rolling warble sustained for several 

 seconds at a time and repeated at very short intervals. It is more varied 

 and slightly more slowly timed than the roll of the Purple Finch and 

 among all the bird songs of almost continuous production it is, to our way 

 of thinking, most pleasing. Often, in the heat of midday, when, for one 

 reason or another, most other species are stilled, the warbling vireo con- 

 tinues its melodious song with little or no indication of lagging. Indeed, 

 it is a warm weather bird, often being silent in the cool of morning or 

 evening, and singing less on cloudy or foggy days than on those marked 

 by bright sunshine. It is a well known trait of the male of this bird to 

 sing while he is taking a turn in the duty of incubation on the nest. The 

 song season lasts from the time the birds first arrive in the region until 

 about mid-July. A male was heard in broken song in Yosemite Valley 

 on July 23, 1915. The call note of the species is a burred zree or szhee. 

 This note may be repeated over and over again in a very insistent tone, 

 in case a jay has entered the nesting precincts of the vireo. 



In a shady spot among some pine trees on the north side of Yosemite 

 Valley, a nest of the Western Warbling Vireo was found on June 17, 1915. 

 It was located 4i/2 feet above the ground at the forking of two almost 

 leafless branches of a coffee berry bush. The nest was, as usual, strapped 

 to and slung within the crotch between the diverging branches. The cup 

 was about 3 inches in outside diameter at the top and about 6I/2 inches 

 from rim to rim around the bottom. One of the parent vireos was sitting 

 on the nest, and the color of its back blended well with the gray bark of 

 the bush and the gray nest material, but its bright black-appearing eye 

 was conspicuous. The bird did not flush until the observer was within 

 four feet of the nest. Two of the four eggs in this nest hatched on June 22 

 and the others were hatched by the 24th. By July 7 this brood had left 

 the nest. Another nest of this species was discovered in a young black 

 oak. It was about 12 feet above the ground and 3 feet out from the trunk. 

 Like the other nest, it was composed of light gray bark fibers and weed 

 stems together with some white egg-cases of spiders. There were 4 tiny 

 young in this nest on June 25 (1915). Upon our visiting the place again 

 on July 7 the then fully feathered young took wing and left the nest as 

 the observer climbed the tree. Some few broods are evidently brought off 

 at later dates, as a family group was seen near Merced Lake on August 23, 

 1915. 



