616 ANIMAL LIFE IN THE YOSEMITE 



Occurrence.- — Common at all seasons in Upper Sonoran Zone on western foothills of 

 Sierra Nevada. Eecorded at nesting time from near Lagrange and at Snelling eastward 

 to Smith Creek (6 miles east of Coulterville) and to near Bullion Mountain. In autumn 

 and early winter appears at higher altitudes eastward as far as Colby Mountain (near 

 Ten Lakes) and commonly in Yosemite Valley; present also in winter season in San 

 Joaquin Valley at Snelling and below Lagrange. In nesting season lives chiefly about 

 blue oaks; but at other seasons of year frequents berry-producing plants especially the 

 mistletoe on oaks. Flocks (openly) through most of year, breaking into attentive pairs 

 at nesting time. 



The Western Bluebird is a species that is likely to be recognized at first 

 sight, even by a beginning student. Nature ha.s produced blue in but a 

 very small number of animals and the species possessing any blue are 

 usually conspicuous because of this color. There are only eight species of 

 really hlue birds in the Yosemite section and among all of these the West- 

 ern Bluebird may be distinguished easily on the basis of other features. 



The jays, including the California, Woodhouse, Blue-fronted, and 

 Piiion, are all of much larger size, and none of them has any chestnut 

 in its plumage. The California Blue Grosbeak is of about the same size 

 as the Western Bluebird and has both blue and chestnut in its scheme 

 of coloration, but its breast is never solidly chestnut and its bill is stout 

 and conical, whereas that of the bluebird is quite slender ; furthermore, 

 the grosbeak is a bird of the stream-side thickets, whereas the bluebird 

 lives as a rule in the more open upland country. The Lazuli Bunting is 

 little more than half the bulk of the bluebird, and the male, who has a 

 buff breast, is white on the belly and of 'lapis lazuli' blue on his back and 

 throat. Both sexes of this bunting have a light wing bar, and the birds 

 keep chiefly to brushy situations. The Western Bluebird may be dis- 

 tinguished from the Mountain Bluebird by its darker tone of blue and 

 bj' the presence of areas of chestnut brown in its plumage. 



In the spring and summer months the local Western Bluebird popu- 

 lation is confined almost entirely to the blue oak belt of the western foot- 

 hills and hence within the Upper Sonoran Zone. The species does nest in 

 small numbers at Snelling, a short distance within the Lower Sonoran 

 Zone, and it also occurs in that season within the margin of the Transition 

 Zone, for example, at Smith Creek east of Coulterville. Although else- 

 where this bluebird is kno\^^l to nest abundantly in the Transition Zone, 

 here at nesting time it avoids that zone almost entirely. Yosemite Valley 

 would seem a very favorable place for the species to nest, but it has never 

 been known to occur there in the summer season. 



In the fall months, however, Western Bluebirds appear at many up- 

 mountain localities not previously tenanted by the species. Several indi- 

 viduals were heard at Glacier Point on September 25, 1915, and flocks 

 were seen on a ridge (Colby Mountain) above Ten Lakes on October 8 



