Greater and Lesser Scaup
By Hugh Jennings
PC: Mick Thompson (Greater Scaup)
Length 18 in 17 in
AOU Band code GRSC LESC
The Greater Scaup (GRSC) is about 18” long while the Lesser Scaup (LESC) is a little smaller at about 17”. The genus name Aythya (AY-thih-ah) is from the Greek aithya, a seabird. Other ducks in the same genus are Canvasback, Redhead, Tufted and Ring-necked Ducks. The species name of the GRSC, marila (mah-RYE-lah), is Latin form of Greek, marile, meaning embers of charcoal, black, in reference to the male’s dark head, neck and breast. The species name of the LESC, affinis (aff-EYE-nis), is Latin meaning adjacent, neighboring, allied, or related to, apparently in reference to the GRSC.
The two scaup are very similar in all plumages. The Greater has a more rounded head and in flight a longer white wingstripe. The Lesser is smaller with a thinner and straighter bill, thinner neck, smaller head with a taller crown which has a more obvious corner at the rear crown. The male in both species has a dark head and breast and dark tail separated by a gray back and white flank. The gray back of the Lesser, on average, has heavier and coarser barring. The oft-mentioned head color differences in scaup are essentially useless in the field. Both species can show bright green or purple gloss, depending on the bird’s behavior and the viewing angle. The females of both are dark brown with small white patches on either side of the base of the bill.
The Greater is the more northerly species and in the summer is found on lakes and bogs in semi-open country near the northern limits of boreal forest, and out into the tundra. The Lesser summers near large marshes in prairie or forested regions. They both winter on lakes, reservoirs, rivers and sheltered areas of coastal bays. They overlap extensively in winter, but the Lesser is far more likely to be found on freshwater lakes and ponds well inland.
The diet of both mostly consists of mollusks and plant material. They forage by diving and swimming underwater, sometimes by dabbling or upending in shallow water. The Greater’s nest is usually very close to water on island, shoreline, or mats of floating vegetation.
The Lesser’s nest is usually on dry land, often on islands in lakes, surrounded by good cover of vegetation. Nests are shallow depressions, lined with dry grass, dead plant material, and down. The eggs of both are olive-buff color, the Greater usually has 7-9 eggs while the Lesser usually has 9-11. Incubation is by the female only, 24-28 days for Greater and 21-27 for Lesser. The young leave the nest shortly after hatching and go to water.
They both migrate in flocks. The GRSC birds from Alaska may winter on either the Pacific or Atlantic coast. The LESC winters along both coasts and across the southern United States.