The Greater Scaup came to the North Basin by the hundreds in late fall and early winter, and then most of them disappeared, leaving a dozen or two as local guests. This week, many more arrived, undoubtedly for a rest break during their northward migration.
The Cornell bird lab website has these “cool facts” about Greater Scaup, which it describes as “the only circumpolar diving duck,” because it breeds across the tundra regions in North America and Europe.
Occasionally an older female Greater Scaup will have male-like head color and male patterning on her back, but she still has the typical white face patch of a female.
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.
The nest of a Greater Scaup is usually lined with a thick layer of down plucked by the mother from her own breast. Nests of poor-condition females may lack down and instead may contain small, grayish-white feathers plucked from beneath the outer body feathers.
Eggs and ducklings fall prey to predators such as gulls, foxes, and ravens. In some areas, northern pike (fish) also eat ducklings.
The oldest recorded Greater Scaup was a male, and at least 20 years, 5 months old when he was found in Michigan in 2007. He had been banded in New York in 1988.https://www.allaboutbirds.org/guide/Greater_Scaup