Greater scaup, black ducks, mallards, and Canada geese are the most abundant wintering birds. Tufted duck, goldeneye, wigeon, teal and possibly goosander with sometimes smew and scaup. Other terrestrial predators include rats, kingfishers, shags, scaup, stoats, and kiwi. The county's most common winter bird is the lesser scaup, a diving duck. Common predators of the greater scaup are owls, skunks, raccoons, foxes, coyotes, and humans. Hens give the namesake discordant "scaup, scaup" call; in courtship drakes produce weak whistles. The greater scaup forms large flocks, some of which can contain thousands of birds. Juvenile greater scaup look similar to adult females. During the summer months, the greater scaup will eat small aquatic crustaceans. In the fall, greater scaup populations start their migration south for the winter. Greater scaup are rated as a species of least concern by the IUCN Redlist. The type species is the greater scaup. Since the 1980s, scaup populations have been steadily decreasing. Greater scaup are a popular game bird in North America and Europe. Lesser scaup become sexually mature in their first or second summer.