Considerably more numerous in North America than greater scaup, and with a much larger breeding range, lesser scaup are the most numerous of our diving ducks.
Smaller and grayer than the greater scaup, the drake lesser scaup in breeding plumage looks black fore and aft, with white sides and a gray back. Late in winter, and in bright light, his back can look almost white. Though black from a distance, once in hand the head shows a slightly iridescent purple, and like the greater scaup’s, it has bright yellow eyes. The head of the lesser scaup is less perfectly round than that of a greater scaup, with a slight bump to the rear. The lesser scaup’s bill is narrower than the greater scaup’s, though it, too, is blue with a black nail at the tip.
Lesser scaup hens are not very vocal compared to dabbler hens, but are more vociferous than greater scaup hens. In flight, they frequently call with guttural brrtt, brrtt, while the drake has a discordant scaup, scaup.
Lesser scaup are much more likely to visit small lakes than are greater scaup, and they are swift fliers with very rapid wing beats that often travel in compact flocks of 25-50 birds. In winter, much of their food is animal matter—clams, crayfish and aquatic insects. Where available, however, they will also eat large amounts of aquatic grasses, seeds, wild celery and wild rice. Although they use salt water and brackish marshes, they are less restrictive than greater scaup.
Except for a few small breeding colonies east of the James Bay and around the Great Lakes, the vast majority of lesser scaup breed in a huge region that begins south of Hudson Bay, dips south through Minnesota and the Dakotas and then sweeps northwest through Montana to the Canadian northwest and into interior Alaska before swinging back again to the Hudson Bay. Minor breeding populations occur in British Columbia, Utah, northern California, Oregon and Washington. More than 600,000 lesser scaup breed in surveyed areas of Alaska, and similar densities occur in the forested parts of the McKenzie River Valley and Old Crow Flats.
The scaup (both lesser and greater combined) breeding population estimate was 3.2 ± 0.2 million in 2006. Scaup declined by 4 percent since 2005, continuing a long-term pattern that has persisted for the last 20 years. They are now 37 percent below their long-term average. The estimate for scaup in 2006 was a record low for the second consecutive year.
“We are especially concerned about the further decline of the scaup, which have reached an all time low this year,” said Don Young executive vice-president of Ducks Unlimited, “DU and others are continuing with targeted research programs on scaup that we hope will soon give us a better understanding of what we can do to help the species recover.”
Related: More on Lesser Scaup