Greater scaup to other diving ducks. The greater scaup forms large flocks, some of which can contain thousands of birds. When flocks are on flowing water, they will face the current, and as the ducks float backwards, some fly to the front of the flock to maintain position. Common predators of the greater scaup are owls, skunks, raccoons, foxes, coyotes, and humans. Greater scaup often find themselves entangled in fishing nets, thus large numbers of them drown in nets each year. Greater scaup can catch avian influenza, so future outbreaks have the potential to threaten greater scaup populations. Although the greater scaup
Lesser scaup well as seeds and other parts of aquatic plants like sedges and bulrushes (Cyperaceae), "pondweeds", widgeon-grass ("Ruppia cirrhosa"), wild celery ("Vallisneria americana") or wild rice ("Zizania"). In winter, but less so in summer, other aquatic animals—crustacean, insect and their larvae and small fishes—form an important part of their diet. It has been reported that both the lesser and the greater scaup have shifted their traditional migration routes to take advantage of the presence of the zebra mussel ("Dreissena polymorpha") in Lake Erie, which was accidentally introduced in the 1980s and has multiplied enormously. This may pose a risk to these