540 ANIMAL LIFE IN THE YOSEMITE 



chat in full song^ as early as 3 :15 in the morning, and it continues to sing 

 until late dusk ; sometimes it breaks forth in the night time. Its best 

 efforts seem to be put forth in the drowsy heat of early afternoon when 

 many other tuneful creatures are silent. During the course of a song 

 the bird often jumps up high into the air and then flutters slowly down 

 to its perch with curiously drooping wings and tail. Although an active 

 bird the chat does not ordinarily display any nervousness of movement 

 as do the smaller warblers, its actions in general being deliberate. 



These birds arrive by the first part of May, having been found already 

 present near Lagrange on May 6, 1919, and they depart by September. 



PiLEOLATED Warblers. Wilsonia pusilla (Wilson)^" 



Field characters. — Half size of Junco. Top of head with a black cap (restricted in 

 females) ; plumage plain yellowish green above, yellow on forehead and on under surface 

 of body. No dark streaks or white markings whatsoever. (See pi. 9gr.) Movements 

 quick and nervous; often flies out to capture passing insects. Voice: Song of male a 

 series of rather flat-toned notes, on about same key, emphasis and intervals between 

 them decreasing toward end of series; call note a similarly flat tchep. 



Occurrence. — Common summer visitant, chiefly to Canadian Zone, on west slope of 

 Sierra Nevada (subspecies chryseola). Also found in spring along eastern base of 

 the mountains and as a migrant through the western foothills (subspecies pileolata) .^^ 

 Lives in thickets over damp ground, usually close to streams, foraging within 6 feet 

 of ground and nesting near or upon the ground. In pairs or solitary. 



In the territory surrounding the Yosemite Valley the small streams 

 and boggy meadows bordered by creek dogwood and willow are frequented 

 by small black-capped yellow birds which are likely to be seen capturing 

 insects close to or within the thickets. The species is the Golden Pileolated 

 Warbler and this territory is its regular headquarters during the summer 

 months. A few of the birds have been seen in summer near the Happy 

 Isles in Yosemite Valley, but the main population at that season is to be 

 looked for in the Canadian Zone above, where pairs are found in favorable 

 country every two hundred yards or so. 



The Golden Pileolated Warblers arrive on the west slope of the Yosemite 

 section at least by April 29 (1916). Males seemingly precede the females 



36 Two subspecies of Pileolated Warbler occur in the Yosemite section. These cannot 

 often be distinguished with certainty in life. 



Golden Pileolated Warbler, Wilsonia pusilla chryseola Eidgway, a slightly smaller 

 more yellowish backed subspecies with an orange tinge ofl the forehead. (See pi. 9g.) 

 It nests in California and is a common summer visitant on the west slope of the Sierra 

 Nevada in the Canadian Zone and locally in the Transition Zone. It was recorded 

 sparingly in Yosemite Valley, and commonly from Hazel Green and Chinquapin eastward 

 to Merced Lake. 



Alaska Pileolated Warbler, Wilsonia pusilla pileolata (Pallas), a darker toned 

 more greenish subspecies of slightly larger size which summers in the Eocky Mountain 

 district and the Northwest, was found to be common in spring at Mono Lake and in 

 small numbers as a spring transient near Lagrange. 



