Lesser scaup in their first or second summer. The oldest known individual reached an age of over 18 years. Before the start of the population decline (see below), about 57% of the lesser scaup nests failed each breeding season because the female was killed or the eggs were eaten or destroyed. The average brood size of nests where eggs hatched successfully was 8.33 hatchlings. Although the lesser scaup has the largest population of any species of diving duck in North America, their population has been steadily declining since the mid-1980s, and reached an all-time low in the early 21sh century. During breeding
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