Aythya marila
Order Anseriformes
Family Anatidae
Subfamily Anatinae
Other names: Blue-bill
♂ Adult male.—Head, neck, upper back, and breast black, the head and neck showing greenish reflections in strong light; middle of back white, marked with narrow wavy black lines; speculum white; a white stripe along wing when spread, lower belly and sides pure white; under tail-coverts black; bill blue-gray; legs and feet lead-color.
♀ Adult female.— Black of male replaced by brown; region around base of bill white; wings brown; speculum and stripe in extended wing white; under parts not so pure white; bill and feet as in male.
The Scaup or Blue-bill is a common migrant along the coast of New York and New England in March and April, and in October and November; it is usually an abundant winter visitant in Long Island Sound, and occurs in winter at least as far north as Massachusetts Bay. Like the other sea ducks it occurs on large inland rivers and on freshwater ponds near the sea.
Blue-bills often occur in very large flocks, and when alarmed they swim toward a common centre, forming a compact bunch, which then swims away from the disturbing factor. They fly in a characteristic waving line, showing a stripe of white along the outstretched wing. The male may be known by his black head, neck, and breast, and by the white back, crossed by wavy black lines. The white face of the female is very conspicuous, and affords an excellent field-mark.
Hoffmann – A Guide to the Birds of New England and Eastern New York (1904)