490 ANIMAL LIFE IN THE YO SEMITE 



their sojourn in the Valley. The grosbeaks often dominate these places 

 to the exclusion of other birds, even the robins; and among the grosbeaks 

 themselves certain individuals seem to be more aggressive than others. 



California Blue Grosbeak. Guiraca caerulea salicarius Grinnell 



Field characters. — Decidedly larger than Junco or Linnet; tail shorter than body; 

 bill heavy, very thick at base. Sexes different. Adult male: Almost solidly dark blue; 

 wing with a broad bar of reddish brown. Female and young: Pale yellowish brown, 

 the wings and tail darker; two light bars across wing. Behavior similar to that of 

 Linnet. Voice : Song of male a rather weak rhythmical warble of short duration and 

 uttered at relatively long intervals; call note of both sexes a sharp clinl\ 



Occurrence. — Common summer visitant in Lower Sonoran Zone. Pound by us only 

 at Snelling. Lives in willows and similar vegetation along river bottoms. To be sees 

 singly or in pairs. 



The California Blue Grosbeak is restricted to the Lower Sonoran Zone 

 where it lives in the low dense thickets of willow on the bottom lands of 

 the big rivers. It is therefore not likely to come to the attention of the 

 mountain-seeking visitor unless he should stop off at some place in the 

 lowlands and make special search for the bird. 



The blue grosbeak takes its name from the color of the male bird which 

 is almost entirely blue of a dark ultramarine hue and not cerulean or the 

 usual sky blue as one of the scientific names of the species would suggest. 

 The female and young birds are almost solidly brown, with no conspicu- 

 ously contrasted markings. Not infrequently breeding males are to be 

 seen which have only a few irregular patches of blue on an otherwise 

 brownish plumage. The males in this imperfect stage have their wing 

 and tail feathers much more worn than those of the males with full blue 

 plumage. This latter fact suggests that the birds in mixed plumage are 

 of the previous season's brood and hence just under a year in age. The 

 flight feathers acquired in the nest (juvenal plumage) are not shed at 

 the first fall molt. These feathers, retained throughout the first year of 

 life, show relatively more wear than the wing and tail feathers of the 

 adults, which are newly acquired at some time in the fall following com- 

 pletion, for the season, of the nesting duties. 



The blue grosbeak is the only one of our emphatically big-billed finches 

 which has blue in its scheme of coloration, and it can be distinguished, 

 as regards the male, on this score alone. The Lazuli Bunting, which is 

 conspicuously blue (of a lighter tone) is much smaller, with white on 

 belly and with a smaller bill. The Western Bluebird is slender of bill 

 and brown of chest. 



During the nesting season the blue grosbeak seems to prefer the vicinity 

 of water, the banks of an irrigating ditch grown up to tall weeds or willows 



