L 40-47 cm, WS 65-72 cm. Versatile in choice of breeding habitat, therefore common: open, clear, oligotrophic lakes in forested areas; densely vegetated, eutrophic lowland lakes and marshes; along seashores; on tundra pools; slow-flowing rivers; reservoirs; park lakes; etc. Mainly migratory. Gregarious when not breeding, forming large, dense flocks.
IDENTIFICATION: Small, short-bodied, with narrow neck and rather large head with crest (long and drooping on breeding male, only a shorter tuft in other plumages) at hindcrown. Head ‘unevenly rounded’ with high forehead and flattish crown; bill short but broad, pale blue-grey with most of tip ‘dipped’ in black. In flight, white wing-bars prominent (as on Scaup). - Adult male breeding: Swimming bird distinctive, has black plumage with sharply defined rectangular white flanks and long drooping crest. Eye yellow. - Adult female: Brownish with paler flanks diffusely blotched darker on most. Resembles Scaup, especially when showing white at bill-base, but told by smaller size, hint of crest, different head shape, darker brown, especially above, and more black at tip of bill. A few have some white on undertail, especially in autumn, recalling Ferruginous Duck, but told by different head shape, hint of crest, and shorter and less prominent white wing-bars. Eye usually deep yellow. - Adult male eclipse: Crest short, flanks dull brown, black parts of breeding plumage tinged brown. - Juvenile: Like adult female, but a little paler brown on head with a little buff feathering at bill-base. Eye brown. Young male attains most of adult plumage in 1st winter (Dec-Mar), but fully only in 2nd winter.
VOICE: Display-call of male a nervously quick, ‘bubbly’ or even giggly series of accelerating notes on slightly falling pitch (also in flight at night), ‘wip wee-weewüwüp’ (‘Turkey in falsetto’). female has growling call typical of Aythya females, ‘krr krr krr …’, slightly faster and higher-pitched, and each segment shorter, than in Pochard; higher-pitched than Scaup.
