BIRDS — CEKTHIADAE — SITTA OAROLINENSIS. 



375 



Third and fourth, quills about equal ; fifth a little shorter ; second intermediate between fifth 

 and sixth. Top of the head and back of the neck, with upper part of back, lustrous greenish 

 black ; rest of upper parts ashy blue. Under parts generally, with sides of head and neck, 

 white, this color extending from the base of the upper mandible over the eye ; tibial feathers, 

 with inner webs of under tail coverts, light rufous brown. Quills white at the extreme base 

 and on the basal portion of the inner webs. Wing feathers dark brown above, except the 

 coverts, the tertiaries, and the ends of primaries and secondaries, which are nearly black, all 

 edged more or less with the color of the back, which becomes more whitish on the tips of the 

 quills and the edges of the outer primaries. Under wing coverts black. Central tail feather 

 like the back ; the rest black, with a broad subterminal band and more or less of the outer web 

 white. 



The female differs only in having the black of the head with an ashy gloss. 



In comparing a large series of specimens together, (about thirty in each,) from the two sides 

 of the continent, the western, as a general rule, have more slender bills than the eastern. I 

 can detect no other difference whatever. This constitutes the character of Mr. Oassin's species, 

 S. aculeata. 



List of specimens. 



SITTA ACULEATA, C as sin. 



Slender-bill Nnthatch. 



Sitta aculeata, Cassin, Pr. A. N. So. Phila. VIII, Oct. 1856, 254. 



Sp. Ch. — Precisely similar to S. carolinensis, but the bill slenderer and more attenuated. 

 Hob. — Pacific coast, and east towards the Rocky mountains. 



It is a very difficult matter to decide whether the western white-breasted nuthatches are to be 

 considered merely as varieties of ;S'. carolinensis or as distinct species. The only difference I can 

 discern is the much slenderer bill, a character, however, which is constant in all before me, (about 

 thirty specimens,) while the stout bill is seen in all east of the Missouri plains. Thus, the 

 depth of the bill opposite the base above is .14 of an inch ; the width at same point is .17, 

 instead of .17 and .22, respectively. Specimens from Washington Territory, however, appear 

 to be intermediate in this respect between more southern and eastern ones. 



The young bird is similar, but duller, the under parts tinged with reddish brown. 



