Greater Scaup Aythya marila Scientific name definitions

This moderately large diving duck is the only circumpolar Aythya, and one of few circumpolar duck species. Less is known about its biology than other North American Aythya— in part because of its relatively isolated breeding grounds but also because of difficulty distinguishing it from its close relative, the Lesser Scaup (A. affinis). In North America, most Greater Scaup nest in coastal tundra of the Arctic and Subarctic, especially western Alaska. Most migrate southeastward across North America to winter on shallow embayments along the northeast Atlantic Coast, particularly in Long Island Sound. Smaller numbers winter farther south along the Atlantic Coast to northern Florida and on the Pacific Coast, mainly from Vancouver, British Columbia, south to San Francisco Bay. The species often occurs in large flocks during molt, migration, and on its wintering grounds. The Great Lakes provide an important rest stop for migrants as they funnel through to the Atlantic Coast.

Up to 80% of the population concentrates in winter in the urbanized northern portion of the Atlantic Flyway—where these ducks are subject to physical disturbances, habitat degradation, and various contaminants. Apparent long-term decline of Greater Scaup wintering in this core region has raised concerns about the welfare of the species and management strategies, as has evidence of dietary changes and elevated levels of organic contaminants and some heavy metals in winter habitats, foods, and the ducks themselves.

At a distance, Greater Scaup are often indistinguishable from Lesser Scaup, and their similarity is a major challenge to waterfowl managers, who require accurate population information for each species to set harvest limits and develop management policies. Unfortunately, because of identification difficulties, the 2 species are combined during aerial (and most ground) population surveys, so changes in populations of either species are obscured—especially those of Greater Scaup, whose numbers are overwhelmed by the more abundant Lesser Scaup.

Life history of North American Greater Scaup as of the mid-1970s was reviewed in Bellrose 1976a Bellrose, F. C. (1976). Ducks, Geese and Swans of North America. Second edition. Stackpole Books, Harrisburg, PA, USA. Close and Palmer 1976 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close . More recently, Allen et al. (Allen et al. 1999 Allen, G. T., D. F. Caithamer and M. Otto. (1999). A review of the status of Greater and Lesser scaup in North America. Arlington, VA: U.S. Fish Wildl Serv. Off. Migr. Bird Manage. Close ) and Afton and Anderson (Afton and Anderson 2001 Afton, A. D. and M. G. Anderson. (2001). Declining scaup populations: A retrospective analysis of long-term population and harvest survey data. Journal of Wildlife Management 65:781-796. Close ) summarized information on the population status of Greater and Lesser scaup from the 1950s through 1997, based on several sets of U. S. Fish and Wildlife Service (USFWS) and Canadian Wildlife Service data-collection programs related to waterfowl management, including temporal population estimates and harvest levels summarized by region. Several food-habit studies, primarily from birds taken during fall and winter hunting periods, have been reported: continental U.S. (Kubichek 1933 Kubichek, W. F. (1933). Report on the food of five of our most important game ducks. Iowa State J. Res. 1:107-126. Close , Cottam 1939 Cottam, C. (1939). Food habits of North American diving ducks. U.S. Department of Agriculture, Washington, DC, USA. Close ), British Columbia (Munro 1941c Munro, J. A. (1941c). Studies of waterfowl in British Columbia: Greater Scaup duck, Lesser Scaup duck. Canadian Journal of Research 19:113-138. Close , Vermeer and Levings 1977 Vermeer, K. and C. D. Levings. (1977). Populations, biomass and food habits of ducks on the Fraser River Delta intertidal area, British Columbia. Wildfowl 28:49-60. Close ), Great Lakes (Jones and Drobney 1986 Jones, J. J. and R. D. Drobney. (1986). Winter feeding ecology of scaup and Common Goldeneye in Michigan. Journal of Wildlife Management 50:446-452. Close , Wormington and Leach 1992 Wormington, A. and J. H. Leach. (1992). Concentrations of migrant diving ducks at Point Pelee National Park, Ontario, in response to invasion of zebra mussels, Dreissena polymorpha. Canadian Field-Naturalist 106:376-380. Close , Leach 1993 Leach, J. H. (1993). "Impacts of the zebra mussel (Dreissena polymorpha) on water quality and fish spawning reefs in the western Lake Erie." In Zebra mussels biology, impacts, and control., edited by T. F. Nalepa and D. W. Schloesser, 381-397. Boca Raton, FL: Lewis Publ. Close , Hamilton and Ankney 1994 Hamilton, D. J. and C. D. Ankney. (1994). Consumption of zebra mussels (Dreissena polymorpha) by diving ducks in Lakes Erie and St. Clair. Wildfowl 45:159-166. Close ), and Long Island Sound (Cronan 1957 Cronan, Jr., J. M. (1957). Food and feeding habits of the scaups in Connecticut waters. Auk 74:459-468. Close , Wahle 1990 Wahle, L. C. (1990). Food habits of Greater Scaup, Aythya marila, and Lesser Scaup, Aythya affinis, in Connecticut coastal waters. Master's Thesis, Univ. of Connecticut, Storrs. Close , Wahle and Barclay 1993 Wahle, L. C. and J. S. Barclay. (1993). Changes in Greater Scaup foods in Connecticut. Northeast Wildl. J. 50:69-76. Close , Cohen 1998a Cohen, J. (1998a). Greater Scaup as bioindicators of contaminants in Long Island Sound. Master's Thesis, Univ. of Connecticut, Storrs. Close , Eccleston 1999 Eccleston, K. A. (1999). Food sources as a factor in the decline of Greater Scaup and Lesser Scaup ducks. Master's Thesis, Univ. of Connecticut, Storrs. Close ). In his volume on comparative waterfowl behavior, Johnsgard (Johnsgard 1965 Johnsgard, P. A. (1965). Handbook of Waterfowl Behavior. Cornell University Press, Ithaca, New York, USA. Close ) described major aspects of social behavior.