260 Distribution of Land Birds. 
tioned Calaveras, lutescent, yellow, Audubon’s, black-throated 
gray(?)*, hermit, Macgillivray’s, western yellow-throatand pileolated. 
The breeding range of the white-headed woodpecker may be taken 
as defining the limits of the Sierra Nevada Area in California. The 
southernmost record of its breeding is from the San Bernardino 
Mountains. Thence it occurs north along the coniferous district of 
the Sierra Nevada Mountains into Oregon. It is apparently more 
narrowly limited to this area than any other species, although some 
other species are nearly equally restricted to the region, as, for ex- 
ample, red-breasted woodpecker, calliope hummer, thick-billed 
sparrow, Louisiana tanager and mountain chickadee. 
Like the Pacific Coast Area, this region exhibits its most charac- 
teristic features toward the north and becomes much less marked 
toward its southern terminus. There is this striking difference, 
however, in the changes which the two areas undergo as we pro- 
ceed northward, that in the coast district we find a gradual change 
in color in the same species, produced by the direct action of the 
environment, while in the Sierra Nevada Area we find a gradual 
introduction of different species characteristic of a more northern 
climate. Examples of the former have already been cited ; of the 
latter, such species as Richardson’s merlin, pigeon hawk, and even 
Kennicott’s screech owl,} doubtless breed in the extreme north of 
_ the State. A number of other northern forms extend their breed- 
ing range still farther south, some reaching the latitude of Lake 
Tahoe, although none of them are found in the southern part of the 
Sierra Nevada Area. Such species are pileated woodpecker, Wil- 
liamson’s sapsucker, Arctic three-toed woodpecker, Oregon jay, 
evening grosbeak, Kodiak pine grosbeak, American crossbill, Lin- 
coln’s finch, and ruby-crowned kinglet. 
_ From the foregoing it will be seen that the Sierra Nevada Area, 
although possessing much in common with the coast fauna, is by 
far the more distinctive of the two as a subdivision of the Boreal 
Province, both in its greater and more continuous southward ex- 
tension, and in the possession of species which are more markedly 
Boreal in form than any occurring in the Pacific Coast Area. 
* My only authority for supposing this species to breed in this area is a record 
from Big Trees, Calaveras County, where it was reported by Mr. Belding as rare in 
July: Proc. U.S. Nat. Mus., 1879, p. 393- It certainly is not a characteristic 
breeder of this area. 
t Townsend: Proc. U.S Nat. Mus., 1887, p. 203. 
