126 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4tH Ser. 
January 5, No. 820, male, June 28, No. 881, female, May 21. 
In the white extreme the dark color of the flanks is much re- 
stricted. Like most of the birds in definitive feather, two in- 
dividuals passing out of the natal down are intermediate, 
having the under wing-coverts gray and white. The amount 
of white is greater in one than in the other, suggesting that 
the two color extremes may occur in the juvenal plumage. 
A series emerging from the down would clear up the whole 
matter and determine whether these variations are to be cred- 
ited to age or to dichromatism. 
Both eyelids are white, and in some specimens there is an 
obscure whitish postocular streak. The suborbital region is 
frequently invaded by white, and the lores are flecked with it 
in several instances. Examples in high plumage have the 
greater and middle wing-coverts and scapulars broadly mar- 
gined with grayish white and the feathers of the upper parts 
between the rump and bill edged with it, quite distinctly pos- 
teriorly and very faintly anteriorly. As in other dark-vented 
species, the crissum is more or less white. In certain speci- 
mens, whitish and brownish filoplumes occur on the crown, 
occiput, and cervix. No. 815 C. A. S. has albinistic feathers 
melanism on the jugulum, and No. 854 C. A. S. possesses 
fourteen fully developed rectrices. The bill of the adult in 
life is black, becoming bluish on the lower mandible between 
the gonys and base; the irises are dark brown; the feet are 
usually flesh-colored, blackish on the outer side (fide Beck and 
Gifford). 
In the Expedition collection there are five nestlings of this 
species representing successive stages of plumage develop- 
ment. No. 920, June 25, is in worn double-down with the 
scapulars just beginning to break from their follicles. Above, 
the specimen is deep mouse gray; below, it is mouse gray, 
relieved by a large grayish white patch on the abdomen and 
by a smaller one on the chest. The same coloration prevails 
in the natal down of the other specimens. No. 921, June 25, 
shows a marked decline in the natal down. The throat, chin, 
lores, orbita, and malar region are partially denuded. Follow- 
ing the lead of the scapulars, the remiges, exterior wing- 
coverts, and contour-feathers of the breast, sides, and upper 
