Anas obscura rubripes.
Vol. XIX ] BREWSTER, An Undescribed Form of Black Duck. 185
1902
chrome to canary or sulphur yellow, the legs and toes bright red,
varying from light scarlet to deep orange, the dark feathers of
the pileum and nape conspicuously margined with gray or fulvous,
and the throat (as well as sometimes the chin, also) profusely
spotted or streaked with blackish. All the dark markings on the
cheeks, throat and neck are broader, blacker and more sharply
defined than in true obscura and they often take the form of coarse,
rounded spots which are seldom if ever present on the head or
neck of the smaller bird.
In typical examples of obscura the bill is greenish black, dusky
olive, or olive green, the legs are olivaceous brown with, at
most, only a tinge of reddish, the pileum and nape nearly or quite
uniformly dark, the throat and chin immaculate, the markings on
the neck and sides of the head fine, linear, and dusky rather than
blackish. In respect to these characteristics obscura does not
seem to vary with age or season for my series includes several
young not sufficiently large and fully feathered to have been able
to fly which are colored and marked precisely like specimens
killed in late autumn, while breeding birds are distinguishable
from the latter only by the more worn and faded appearance of
their plumage. The males of both forms, however, are almost
invariably larger than the females as well as more richly colored
and heavily marked, especially on the head and neck; a fact
which should be borne carefully in mind when specimens of the
two are compared.
Both races are evidently subject to a good deal of individual or
geographical variation which tends to connect them by a series of
intergrading specimens. Thus I have small birds with grayish
crowns or streaked throats and even one or two which, in life,
apparently had yellow bills and red legs, while several of the large
ones have plain black crowns or immaculate throats. I have yet
to see a specimen of obscura, however, which possesses the coarse,
rounded, deep black spots that are usually present in greater or
less numbers on the neck, as well as often on the throat, of
rubripes.
The existence of a small percentage of non-typical examples,
like those just mentioned, does not necessarily affect the diagnos-
tic value of the characters to which I have called attention.