562 



ANIMAL LIFE IN THE YOSEMITE 



with its peculiar manner of movement. Even experienced observers are 

 sometimes put to considerable effort in locating and following one of the 

 birds. The brown back with its narrow streaking of light color harmonizes 

 closely with the warm tones and up-and-down pattern of the bark. (See 

 pi. lOh.) Only in side view, when the white under surface shows, and 

 then especially if the bark be wet and so darkened, is the creeper likely to 

 be seen easily. 



The Sierra Creeper keeps closely to one restricted sort of environment, 

 namely, the trunks and larger branches of trees. In our experience we 

 do not recall a single exception to this rule. True enough, one of these 



birds was seen scaling up the slabs of cedar 

 bark covering the exterior of the Camp 

 Curry dining room, but even there the 

 bird was obviously in its proper niche. 

 The creeper's whole scheme of existence, 

 its manner of foraging and of nesting, is 

 more limited and specialized than is that 

 of almost any other bird in the region. 



When on the trunk of a tree the 

 creeper's progress is always upward. 

 Sometimes it moves sidewise a short dis- 

 tance, though always with steeply diagonal 

 posture; often it spirals around the bole 

 while ascending, and occasionally the bird 

 will drop down a step or two ; but it never 

 runs down the tree or even turns head 

 downward, as do the nuthatches. After 

 ascending to near the top of one tree the 

 creeper flies down to near the base of the 

 same or a neighboring tree and there starts 

 a fresh ascent. 



It moves spasmodically, hopping or 'hitching' upward a few steps, 

 then stopping to make inspection when it sees anything of possible service 

 such as food. The tail with its stiffened and pointed feathers is used 

 habitually to give the bird support (fig. 58a). The bird turns its head 

 this way and that, peering into crannies in the bark, and by means of the 

 slender curved bill, used as tweezers, readily picks out insects from the 

 deeper crevices. 



The creeper seems never to be at rest. Whatever the time of the day, 

 it is on the move. The query arises : Do these birds need to forage inces- 

 santly, do they have to keep continually active in order to get sufficient 

 nourishment ? Or is part of their activity a matter of habit or an expendi- 



Fig. 58. Tails of (a) Sierra 

 Creeper and (b) Eed-breasted Nut- 

 hatch. The Creeper uses its tail 

 as a prop, after the manner of a 

 Woodpecker, and hence climbs 

 chiefly or altogether upward on 

 trees; the Nuthatch makes no use 

 of its tail for support and the bird 

 moves in any direction on a tree. 



