WESTERN BLUEBIRD 273 



Field marks. — There are several partially or largely blue birds on 

 the Pacific slope, but not one is so intensely blue as the male western 

 bluebird; the rich blue of his head, wings, and tail and the deep chest- 

 nut on his breast are distinctive marks. The jays are all much larger, 

 the blue grosbeak does not have the solidly chestnut breast and its 

 stout bill is quite noticeable, and the lazuli bunting is a much lighter 

 blue and has white wing bars. The colors of the female are similar to 

 but much paler and duller than those of the male. The mountain 

 bluebird, in its pale soft colors, is not likely to be confused with the 

 western, as there is no chestnut in the plumage of either sex. 



Fall. — Theed Pearse writes to me that, on Vancouver Island, some 

 birds, possibly local breeding individuals, move southward very early, 

 during the last of June or the first two weeks in July. Other migrating 

 parties pass through in August and as late as October 20, consisting 

 of bluebirds, Audubon's warblers, robins, and cedar waxwings. Mr. 

 Rathbun tells me that the western bluebird is a very common migrant 

 during the latter part of October in western Washington. Grinnell 

 and Storer (1924) write: 



The manner of association during the season of molt has not been observed, but 

 by September flocks have been formed which include both adult and immature 

 birds, and in this fashion they spend the winter. The flocks, in observed instances, 

 included from 6 to 25 members. Sometimes other birds are associated. In 

 Yosemite Valley we saw Western Bluebirds in company with Audubon Warblers 

 on one or more occasions, and Mr. C. W. Michael (MS) reports Western and Moun- 

 tain Bluebirds together there during November of 1920. Western Bluebirds and 

 Robins are frequently seen together during the winter months though the two 

 do not flock with each other in the usual sense of the word." 



They say that there is an up-mountain movement of the bluebirds 

 in fall in the Yosemite region and that they are seen at high altitudes 

 all through the late fall and early winter. "The attraction for these 

 birds at these higher altitudes is the abundant supply of food in the 

 form of mistletoe berries. This food supply, rather than weather, 

 short of extremely severe storms, seems to be the factor regulating the 

 stay of the bluebirds in the mountains. That snow alone is no particu- 

 lar deterrent to the birds' stay is shown by our observations made on 

 the stormy morning of December 10, 1914, at Mirror Lake, when 

 bluebirds were flying about actively, now and again alighting on the 

 snow-weighted mistletoe clumps. Masses of the snow would be dis- 

 lodged and shower the observer beneath, but the birds themselves 

 seemed in nowise discommoded." 



Mr. Cogswell writes to me: "This species is varyingly numerous in 

 lowland areas from late in summer to early in spring but is usually 

 abundant in the foothill areas around Pasadena and in the more open 

 mountain canyons below snow level. Several were seen in Bear 



