Aythya affinis
Order Anseriformes
Family Anatidae
Subfamily Anatinae
Other names: Little Blue-bill
Adult.— Similar to the [Greater Scaup] but smaller, and head and neck of male showing at close range purplish instead of greenish reflections.
The Lesser Scaup Duck is a common migrant off Long Island and in the lower Hudson Valley, occurring in September and October, and in February and March; in New England it is less common, and appears generally in the autumn, often in company with the following species. It occurs both on the coast and in inland ponds. It is doubtful whether it occurs in winter, though the Greater Scaup is common at that season. The two species resemble each other very closely, but may be distinguished in good light and at close range by the color of the head, which is purplish in the Lesser, greenish in the Greater.
Hoffmann – A Guide to the Birds of New England and Eastern New York (1904)