Lesser scaup that looks strongly curved or even angular due to the small crest. When the birds raise their heads, these differences are most easy to spot, and after observing the two species in direct comparison it usually becomes easy to recognize. In fact, in alternate plumage the lesser scaup drake may appear identical in shape and size to a drake of the ring-necked duck ("A. collaris"); the black back and wings of that species are hard to confuse with the light ones of the lesser scaup male though. Particularly in the case of vagrant birds in Europe, the identification is complicated
Lesser scaup of James Bay and the Great Lakes. Notable breeding concentrations, with more than half a million birds at the height of the season, can be found in Alaska, in the woodlands of the McKenzie River valley and on the Old Crow Flats. These birds migrate south (mostly via the Central and Mississippi Flyways) when the young are fledged and return in early spring, usually arriving on the breeding ground in May. Lesser scaup typically travel in flocks of 25–50 birds and winter mainly on lakes, rivers and sheltered coastal lagoons and bays between the US–Canada border and northern Colombia, including