One of the most abundant of North American ducks: the Lesser Scaup is a widespread breeding bird in Canada and northern USA and a common wintering bird in the southern states (extending much farther south than the Greater Scaup Aythya marila). It is a regular trans-Atlantic wanderer — since the first accepted record in Britain in 1987, more than 150 have been reported here, but because of confusion with Tufted Duck hybrids, identification is challenging.
Shape and structure help separate the Lesser from the Greater Scaup. It is slightly smaller, looks less powerful, has a smaller bill and the head shows a distinct bump or small crest at the rear of the crown. The female’s head often appears much darker than the body.
Though both habits and behaviour are similar to the Greater Scaup, this species shows a much greater preference for freshwater. Similarly, while wintering, gatherings often number thousands of birds. Where it comes into contact with man, such as town parks, it will become tame and confiding.
Lesser Scaup is a well-established species in collections, though much commoner in North America than Europe. Clutch size is 8-10 eggs, with incubation 23-25 days.
CornellLab. (2021). All About Birds, Lesser Scaup ID
Stoddart, A. (2019). BirdGuides Tufted Duck, Greater Scaup and Lesser Scaup photo ID guide