Greater scaup is fairly shallow and has an abundance of food sources and cover. The female lays six to nine olive-buff-colored eggs, which she incubates for 24–28 days. A larger clutch could indicate brood parasitism by other greater scaups or even ducks of other species. Newly hatched chicks are covered with down and are soon able to walk, swim, and feed themselves; however, they are not able to fly until 40–45 days after hatching. The vulnerable small chicks follow their mother, who protects them from predators. The greater scaup dive to obtain food, which they eat on the surface. They mainly eat
Lesser scaup bill may give a hint; in the lesser scaup it has a stronger curve on the upperside than in the greater, resulting in a distal part that looks somewhat flattened and wide in the lesser scaup—hence the vernacular name "broadbill". If the birds fly, the most tell-tale sign is the white secondary remiges, whereas in the greater scaup the white extends on the primary remiges also, i.e. far towards the wingtip. Lesser scaup females show the characteristic darker iris (bright yellow in greater scaup males and females) at closer distances. Lesser scaup drakes in nuptial plumage are often said to