Greater Scaup Aythya marila is very similar to the Lesser Scaup Arthya affinis. The latter tend to prefer freshwater ponds and lakes while the former prefer lakes and saltwater bays, but this is not absolute. A better criteria is the extensiveness of white on the secondaries and primaries seen while in flight. This white is more extensive in the Greater Scaup as shown in photos 6159 and 6161.