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
Greater scaup because they look almost identical from the air. It was estimated that the greater scaup made up about 11% of the continental scaup population. Since the 1980s, scaup populations have been steadily decreasing. Some of the primary factors contributing to this decline are habitat loss, contaminants, changes in breeding habitat, and a lower female survival rate. The 2010 American scaup population survey was 4.2 million scaup, however, the worldwide greater scaup population survey estimated 1,200,000 to 1,400,000 mature greater scaup. Along with the aerial population surveys, there is a banding program for the greater scaup. Metal leg bands are placed