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
Greater scaup molluscs, aquatic plants, and aquatic insects. During the summer months, the greater scaup will eat small aquatic crustaceans. There is a report of four greater scaups in April near Chicago swallowing hibernating leopard frogs (with body length about ), which they dredged out of a roadside freshwater pond. In freshwater ecosystems, the greater scaup will eat seeds, leaves, stems and roots, along with sedges, pondweeds, muskgrass, and wild celery. Owing to the greater scaup's webbed feet and weight, it can dive up to and stay submerged for up to a minute, allowing it to reach food sources that are unobtainable