This species is not much inferior in size to the eider duck. The bill is
almost two inches long, of an orange-colour; at the base of the upper
mandible is a ridged protuberance, flat on the top, and compressed on
the sides, but divided into two, the elevated parts velvety black,
passing on each side to the eyes; the crown of the head and nape are
pale ash-colour; at the base of the upper mandible the feathers are
pea-green, passing backwards on each side the neck, and taking in half
the eye; beneath which, and round to the chin, the feathers are of a
dirty white; but here the two colours are blended, and the white is lost
by degrees in the green; under the chin is a black mark, diverging like
the letter V inverted: the rest of the neck and breast are whitish; the
middle of the back, the belly, and vent, black; wings dusky; on the
middle of the coverts is a patch of white; quills black; the secondaries
curve downwards over the quills; the shafts deep ferruginous, on each
side the outer ones a patch of white; the tail is cuneiform, short, and
black; legs dusky; the windpipe, according to Captain Sabine, is
precisely like that of the eider duck.
The female is less; the protuberance on the bill not so large, nor so
high-coloured, but the feathery ridge on the top is broader; the whole
plumage brown, the middle of each feather dusky; six of the lesser
quills are tipped with white, which forms a line of white on the wing;
the rest of the quills and tail brown.—_Montagu._