Courtsey Kenn Kaufman
The Lesser Scaup’s breeding range stretches from Alaska to Ontario and dips southward through the Great Plains to northern New Mexico. Nearly 66% of all Lesser Scaup breed in Canada’s boreal forest region. This diving duck winters across a broad range from Washington south into Nicaragua, and from Central California east through Texas. The winter range also covers almost the entire eastern United States south of a line roughly from Texas through the Great Lakes to southern New England.
A legend for the range map to the right can be found here
While some Lesser Scaup winter coastally, open, shallow freshwater is used most often. Lesser Scaup breed on the shallow lakes and ponds of the boreal forest and seasonal pools of prairie potholes, where spring vegetation is emerging and underwater vegetation is abundant. The only North American diving duck to breed at significant elevation, this scaup also breeds in the Rocky Mountains. During migration and winter, large lakes, ponds, rivers, reservoirs, near shore coastlines, saltwater bays, and estuaries are important sites for this duck.
The Lesser Scaup is well adapted for aquatic foraging; its feet are set so close to its tail that diving is efficient, although walking is a little clumsy. Usually in freshwater water 5 feet, but occasionally up to 20 feet deep, the bird dives at an angle and resurfaces far from the initial dive. The seeds of aquatic plants such as yellow pond lilies and bullrushes, and the soft parts of waterweed and pondweed are important foods year round. Animal prey includes leeches, snails, amphipods, fingernail clams, surf clams, zebra mussels, shrimp, herring eggs, small fish, and surface insects like midges. The scaup’s diet varies with the season and food abundance.
During spring migration, Lesser Scaup form monogamous pairs. Courtship displays include a quick head toss accompanied by a quiet “wheee-ooo.” Females respond with an extended neck, raised bill, and a growl call. While Lesser Scaup drakes do not defend territories, they do attack other males during egg laying. Located in thick, new vegetation, usually near water, the nest is a simple depression lined with grasses and finished with down. The female incubates 8 to 10 olive eggs for 21 to 27 days, during which time the male departs. Where breeding densities are high, Lesser Scaup may lay eggs in other ducks’ nests; in turn, they sometimes host Redhead, Gadwall, and Ruddy Duck eggs.
The downy chicks can walk, swim, and dive within a day of hatching. After the female Lesser Scaup leads them to water, chicks feed independently on surface insects for about two weeks until they are heavy enough to remain underwater. Lesser Scaup hatchlings from different clutches sometimes form crèches, which one or more adult females may defend. Lesser Scaup can fly between 47 and 61 days of age.
In shapeless groups or V-formations, Lesser Scaup migrate at night and respond to weather patterns like hard freezes and approaching fronts. Migration patterns shift with food availability, so that flyways are not closely followed. Fall migrants often depart in large groups that can number in the thousands. Fall migration can be delayed by molting; most Lesser Scaup migrate in late October to mid-November, making them one of the latest arrivals on the wintering grounds. Spring migration begins as early as late February and extends well into May.