Lesser scaup Lesser scaup The lesser scaup ("Aythya affinis") is a small North American diving duck that migrates south as far as Central America in winter. It is colloquially known as the little bluebill or broadbill because of its distinctive blue bill. The origin of the name scaup may stem from the bird's preference for feeding on scalp—the Scottish word for clams, oysters, and mussels; however, some credit it to the female's discordant scaup call as the name's source. It is apparently a very close relative of the Holarctic greater scaup or "bluebill" ("A. marila"), with which it forms a superspecies. The
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