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 scientific name is derived from Ancient Greek "aithuia" an unidentified seabird mentioned by authors including Hesychius and Aristotle, and Latin, "affinis" "related to", from its resemblance to the greater scaup. Adults are long, on average. The species can weigh ; males weigh on average and weigh noticeably less, at on average. Wing lengths (not wingspans) are about in males and in females; the tarsus is about long, and the bill . The wingspan is . The adult males (drakes) in alternate plumage have a black, iridescent head and a small tuft at the hindcrown, a black breast, a whitish-grey back