Lesser Scaup (Aythya affinis)

Reifel Migratory Bird Sanctuary, British Columbia, April 2001
400mm 1/500sec f/8

 

This article originally appeared in the Fall 2001 issue of Marshnotes^®, published by the British Columbia Waterfowl Society, Delta, BC.

There are two species of Scaup in North America. The Greater Scaup occurs throughout the Northern Hemisphere while the Lesser Scaup only occurs in North America. It has been estimated that Lesser Scaup make up almost 90% of the North American scaup population.

Scaup are the most numerous diving duck in North America. Diving ducks feed on small animals and plant material by diving beneath the surface of the water unlike marsh ducks that feed from the surface by tipping. In this way diving ducks can find food in deeper water than marsh ducks. To help them swim under water, diving ducks have legs placed farther apart and closer to their tails than marsh ducks, although this makes walking on land awkward. Unlike marsh ducks, diving ducks need a running start across the surface of the water to become airborne.

Scaup are easy to recognize but distinguishing between the two species is difficult. The males of both species have a dark head, chest, and tail, and white sides. Females of both species are brown, with white at the base of the bill. Both species have pale blue bills. In flight they are the only ducks in North America with a broad white stripe on the upper trailing edge of the wing.

Lesser and Greater Scaup males are very difficult to distinguish in the field and females are almost impossible. Female Greater Scaup sometimes have a light colored ear patch but this can be lost at certain times of the year. After observing mixed flocks of both Greater and Lesser Scaup at close range, the best features I have found to distinguish the males are the head color and shape. In the right light, Lesser Scaup have a purple gloss, and Greater Scaup have a green gloss. Also, the head of a Greater Scaup is more rounded than the Lesser Scaup, which has a subtle crest on top of its head. The purple gloss and subtle crest of the lesser scaup are visible in teh above photograph.

Lesser Scaup are common at the Sanctuary all year except in the summer when most have migrated inland to the interior of British Columbia, Alberta, or farther north to breed. You can often find scaup in the Sanctuary in the fall, winter, and spring in the deeper brackish water of the southwestern pond.

- text © David Blevins