The Greater Scaup is a medium-sized diving duck with a rounded head. They measure 39 to 56 centimeters in length, with a wingspan of 72 to 79 centimeters. At a distance, breeding male Greater Scaup are black and white, but closer views reveal an iridescent green sheen on the head, super thin black barring on the back, a bluish bill, and a yellow eye. Females are brown overall with a darker brown head and a white patch next to the bill, but the size of the white patch varies. Nonbreeding males look like a cross between a female and a breeding male: a mottled brown-and-gray body and a blackish head. During migration and winter, Greater Scaup form large flocks on bays, lakes, and larger wetlands. They tend to form tight groups with each other and sometimes mix with other diving ducks. Breeds in shallow lakes and ponds in treeless wetlands in the tundra. During winter, look for Greater Scaup on coastal bays, lakes, and reservoirs. The conservation status of this species is Common Bird in Steep Decline.
Eggs and ducklings fall prey to predators such as gulls, foxes, and ravens. In some areas northern pike (fish) also eat ducklings.
Once incubation begins, the male Greater Scaup leaves the female and goes to molt on a relatively large, isolated lake with abundant food and cover. These lakes are used year after year during molt and may be in the immediate vicinity of the breeding wetlands or many miles away.
Source: Greater Scaup Overview and Identification Information, All About Birds, The Cornell Lab of Ornithology