550 ANIMAL LIFE IN THE YOSEMITE 



greasewood stems overhung by sprays of foliage of the same plant. The 

 nest rim was 31 inches (770 millimeters) above the ground. There were 

 3 eggs, one infertile, one half-incubated, and the third nearly ready to 

 hatch. The second nest was found on May 12. It was situated in a small 

 live oak which was growing at the side of a grassy glade bounded by 

 chaparral. The nest was 57 inches (1440 millimeters) above the ground 

 at the rim, and was supported upon a tangle of twigs as well as by the 

 slanting main trunk of the tree. The material used was chiefly dead twigs 

 of greasewood with a few shreds of bark from the same shrub. The 

 interior was lined with smaller twigs and rootlets. Outside, the nest 

 measured approximately 7i/^ by 12 inches (190 by 300 millimeters), while 

 the saucer-shaped depression was about an inch deep and 4 inches across 

 (25 by 100 millimeters). This nest was well shaded from above, although 

 in plain view from the side. At 7 :30 in the morning it contained two 

 fresh eggs, and a third was added by 2 :20 p.m. the same day. 



Thrashers obtain much of their food by digging with their long bills 

 in leafy debris under bushes; and this habit, when they chance to forage 

 in gardens, brings them into disrepute. At the Campbell place above 

 Pleasant Valley the birds were said to have practically dug up the garden 

 during the summer of 1915. This is only likely to occur where cultivation 

 is attempted close to chaparral-covered areas. General clearing and tilling 

 of the land ordinarily results in the thrashers withdrawing from the 

 vicinity altogether. 



Rock Wren. Salpinctes obsoletus obsoletus (Say) 



Field characters. — Size nearly that of Junco; bill long and slender. Upper surface 

 light grayish brown; under surface whitish, lightly flecked with dusky on breast; tail 

 with a subterminal blackish bar and light tip. Body bobbed down and up at frequent 

 intervals. Voice: Song a series of burred and clear notes of varying pitch, with occa- 

 sional rests, chr, chr, chr, trr, ter, ter, eche, eche, chr, etc. ; call note a clear tinkling trill. 



Occurrence. — Common in summer at numerous points in the Yosemite section from 

 near Merced Falls eastward across the Sierra Nevada to Williams Butte; ranges up to 

 timber line; in winter disappears from the higher country, but remains all the year 

 below level of heavy snow. Lives in rocky situations, either on broken outcrops or about 

 masses of slide rock; also, in winter, on earth walls of gullies. Solitary. 



The Rock Wren is one of a considerable group of birds and mammals 

 whose local distribution is dependent upon the presence of a particular 

 type of habitat. In the case of this bird the special requirement is met 

 in bare, steep, or broken surfaces of rock or of hard-packed earth. The 

 domes and rock slides of the high Sierras, the outcrops on the sides of 

 the lower Merced Caiion, and the earth bluffs near Snelling afford suitable 

 conditions for the species. In winter the mountains are deserted, the birds 



