460 ANIMAL LIFE IN THE YOSEMITE 



the bird takes ta flight the tail is seen to be broadly margined with white. 

 The young in the juvenal plumage, which they acquire in the nest and 

 wear until the first fall molt, are streaked over the whole body, and they 

 lack any indication of the black cowl, but their white outer tail feathers 

 are just as conspicuous as those of the parent birds. The middle of the 

 back and sides of the body are reddish brown in the adult Sierra Junco, 

 a feature which helps to separate this species from the near-related Shu- 

 feldt and Slate-colored juncos. No other bird is likely to be confused 

 with the junco. The Spurred Towhee has a black cowl similar to that 

 of the junco, but the former is a much larger bird, has white spots on 

 the black wings and tail, and stays almost exclusively within heavy brush, 

 instead of foraging out on open ground. 



The Sierra Junco, in summer, is found throughout the main forest belt 

 of the Sierra Nevada. It eschews dense growths of timber, preferring to 

 live in clear areas beneath the larger trees or between tracts of timber, 

 but always where there is convenient cover close by, to be sought if danger 

 threatens. The bird gains the greater portion of its forage on open ground 

 and nests there, but it uses the trees and large bushes as song perches 

 and as safety refuges. In winter a lesser degree of restriction in habita- 

 tion is evident, for then the juncos invade all sorts of vegetational environ- 

 ments save open prairie where no cover of any sort is available. 



The total junco population on the Sierra Nevada during the summer 

 months is in excess of that of any other one species of bird. Three to five 

 an hour will usually be seen at this season in any part of its range, save 

 perhaps in Yosemite Valley. The Sierra Junco is outnumbered by the 

 Western Chipping Sparrow on the floor of the Valley, but it is much 

 better represented in the zones above, especially in the Canadian. The 

 junco population is larger, relatively as well as absolutely, on the west 

 slope of the Sierras than on the east slope. The winter distribution is 

 less uniform. Then the birds are in flocks and their inclusion in a census 

 depends upon the observer's meeting one of these companies, which may 

 aggregate 15 to 50 birds. 



Many juncos remain in the highlands through the crisp fall weather, 

 and the birds are then present literally in droves in the red fir territory 

 immediately above and surrounding the Yosemite Valley. But the first 

 flurry of snow, forecasting the approach of winter, starts them do^vn-slope 

 rapidly and soon relatively few remain even as high as Yosemite Valley. 

 Some depart for the lower altitudes by October; these are joined later 

 by those which linger until they are literally forced out of the high 

 mountains by the snow mantle which covers up their food supply there. 

 The bulk of the population at this season is concentrated in the foothills, 

 but some go down still farther to the west, into the San Joaquin Valley. 



