COWBIEDS 399 



of willows bordering the Merced River. A pair of Dwarf Cowbirds was 

 seen near the Tuolumne River, 2 miles below Lagrange, on May 8, 1919, 

 but no evidence as to their breeding activities was obtained, nor did we 

 chance to find Cowbirds' eggs in any of the birds' nests examined there. 

 At Mono Lake in the season of 1916 a number of Nevada Cowbirds 

 Avere obtained. Two birds taken on May 10 showed little sign of breeding 

 activity, but a female obtained May 23 contained an egg nearly formed 

 which probably would have found its way into the nest of some small 

 bird the following morning. It is to be recalled here that the female 

 Cowbird is a shirker in that she deposits her eggs, singly, in the nests of 

 other birds, usually species smaller than herself. She thus foists upon 

 these other birds the duties of incubating her eggs and rearing her off- 

 spring. On May 31 a second female was taken which contained a good- 

 sized yolk. Another bird taken the same day was a non-breeder, possibly 

 having failed to find a mate. On June 17 a third female was taken which 

 gave indications of laying activity close to the time of capture. Cowbirds 

 were heard in the corrals at the Farrington Ranch near Williams Butte 

 on September 14, 1915, but since none was obtained nor any others observed 

 during the subsequent week when intensive field work was carried on in 

 the vicinity, this may have marked the last appearance of the species in 

 the region for that season. 



Yellow-headed Blackbird. Xanthocephalus xanthocephalus (Bonaparte) 



Field characters. — Male slightly larger than Robin; head, neck, and breast bright 

 yellow; small patch on wing white; plumage otherwise dull black. Female smaller than 

 a Robin ; body dark brown, not streaked ; head, fore neck, and breast dull yellow. Voice : 

 A'arious harsh and scolding notes, recalling Red-winged Blackbird but distinctly different. 



Occurrence. — Uncommon transient. Recorded near Williams Butte, April 27, 1916, 

 and May 11 and 12, 1916, and Yosemite Valley, "about January, 1917." Reported from 

 Dudley, six miles east of Coulterville, in spring. 



The Yellow-headed Blackbird belongs to the fields and marshes of the 

 lowlands, hence is not often encountered in the Yosemite section. None 

 was seen by us during our work in the western part of the region, and 

 only three were noted in the vicinity of Mono Lake. 



A male bird in full adult plumage was seen near Williams Butte on 

 April 27, 1916, and other individual males were collected on May 11 

 and 12 of the same year ; these latter lacked the white wing patches, and 

 so were probably yearlings. In 1919 there was exhibited in the Park 

 Superintendent's office in Yosemite Valley, a male Yellow-headed Black- 

 bird which was said to have been killed "almost at the door of Sentinel 

 Hotel about January, 1917." It was obviously a stray wanderer from 

 some point on one side or the other of the Sierras. 



