White-winged Scoter Melanitta deglandi Scientific name definitions

The White-winged Scoter nests on freshwater lakes and wetlands in boreal forest in the northwestern interior of North America, and overwinters primarily along the coasts of the Pacific and Atlantic oceans. This species is closely related and, until recently, considered conspecific with Velvet Scoter (Melanitta fusca) of western Eurasia and Stejneger's Scoter (M. stejnegeri) of northeastern Eurasia. It differs in appearance from these species by the coloration of the flanks, and the shape and coloration of the bill (see Appearance: Similar Species).

Similar to other Melanitta, the White-winged Scoter runs and flies along the surface of the water for a short distance when taking off. Once in the air, its flight is swift and direct, powered by a rapid wing beat. Individuals often fly low over the water in lines referred to as strings, but most of their time is spent loafing or swimming on the surface. They feed almost exclusively by diving, generally taking prey on or near the bottom. Molluscs (e.g., Blue Mussel, Mytilis edulis) and crustaceans are important foods on wintering areas—generally open coastal environments, especially bays and inlets, where food is likely to be most abundant. On its breeding areas, this species favors large wetlands and lakes, either brackish or freshwater sites. Foods on breeding areas include crustaceans (especially the amphipod Hyalella azteca) and insect larvae distributed along or near the bottom.

This species is serially monogamous—the male leaves his mate soon after she begins laying eggs. Females sometimes nest in high densities on islands, but more often appear to nest up to several kilometers from water. Nests are typically hidden beneath dense, thorny vegetation, such as gooseberry (Ribes) or rose (Rosa) bushes. Individuals return to the same general area to nest in subsequent years and may even use the same nest bowl. The survival rate of young White-winged Scoter is low, with most mortality occurring in the first few weeks of life.

Although classified by BirdLife International as Least Concern because range and population sizes are large (1 BirdLife International (2020). .Species factsheet: Melanitta deglandi Close ), the status and trends of populations are poorly known due to remoteness of breeding areas and because large-scale waterfowl surveys pool data for North American scoter species. Still, available data suggest that White-winged Scoter populations have decreased in recent decades (2 North American Waterfowl Management Plan, Plan Committee. (2004). North American Waterfowl Management Plan 2004. Inspection framework: Strengthening the biological foundation. Canadian Wildlife Service, U.S. Fish and Wildlife Service, Secretaria de Medio Ambiente y Recursos Naturales. Close , 3 Nisbet, I. C. T., R. R. Veit, S. A. Auer and T. P. White. (2013). Marine birds of the eastern United States and the Bay of Fundy: Distribution, numbers, trends, threats, and management. Edited by P. A. Buckley. Vol. 29. Cambridge: Nuttall Ornithological Monographs. Close ; see Population Status). This species is vulnerable to oil spills because it often occurs in high densities along oil transportation routes (188, 189, 190, 191); it is threatened in winter because it feeds at depths (30–40 m) that make it prone to being trapped in fishing nets (192); and it may be highly susceptible to broad-scale oceanic regime changes, that affect both biological and climatic variables (194, 195). Although not generally prized by sport hunters, significant numbers are shot each year, especially along the Atlantic Coast. Because of this species' low rate of recruitment and strong philopatry to nesting areas, disturbance during the nesting season could also impact local populations. These potential threats underscore the need for better population data.