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The Greater Scaup (Aythya marila) has been identified as a focal species of management concern due to declines in the combined breeding population of Greater and Lesser Scaup in North America and evidence of scaup declines in the United States in mid-winter surveys and the Christmas Bird Count. Population estimates for Greater Scaup alone are difficult to determine because they cannot be distinguished from Lesser Scaup (Aythya affinis) during surveys. Numbers of breeding scaup in the tundra and the eastern boreal forests of Canada, which are primarily Greater Scaup, appear to be stable over the long term. Some Greater Scaup also breed in the western boreal forest of Canada and Alaska, which is in the core of the Lesser Scaup breeding range; it is unclear whether both species contribute to the negative trend observed there. On migration and wintering areas, there are serious concerns regarding threats to scaup habitat. Major threats include habitat loss and degradation due to reduced water quality and human development, contaminants, invasive species altering food resources, and human disturbance. Invasions of zebra and quagga mussels in the Great Lakes, an important migration and wintering area for Greater Scaup, has resulted in substantial changes in the feeding ecology of scaup and likely contributed to a shift in numbers wintering on the eastern Great Lakes from the northern Atlantic coast.
Date: July 2009
Sources: 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.
Austin, J.E ., A. D. Afton, M. G. Anderson, R. G. Clark, C. M. Custer, J. S. Lawrence, J. B. Pollard, and J. K. Ringelman. 2000. Declining scaup populations: issues, hypotheses, and research needs. Wildlife Society Bulletin 28:254-263.
Badzinski, S. S., and S. A. Petrie. 2006. Diets of Lesser and Greater Scaup during Autumn and Spring on the lower Great Lakes. Wildlife Society Bulletin 34:664-674.
Kessel, B., D. A. Rocque, and J. S. Barclay. 2002. Greater Scaup (Aythya marila) . The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology. Retrieved July 2009 from http://bna.birds.cornell.edu/bna/species/650.
U.S. Fish and Wildlife Service. 2009. Waterfowl population status, 2009. U.S. Department of the Interior, Washington, D.C. USA.
Species Profile from NatureServe
Greater Scaup Aythya marila
Description:Medium-sized diving duck.
Life History:Clutch size averages about 8-9. Incubation: 23-27 days, by female. Males usually abandon females in early incubation. Young are tended by female, fledge in 9-10 weeks. May nest in colonies of 50+ pairs. May gather in winter flocks of up to 50,000 individuals.
Habitat:In migration and winter, found in bays, estuaries, and large open inland lakes and rivers. Breeds near shores of ponds and lakes, in marshes, or on islands, primarily in forested tundra and northern borders of the taiga; among grass or shrubs, or under spruce boughs. The nest is a hollow lined with plant material, down and feathers.
Estuarine Habitat(s): Bay/sound, Lagoon, River mouth/tidal river
NatureServe Status: Global Status: G5, Global Status Last Reviewed: 21Nov1996, Global Status Last Changed: 21Nov1996, Rounded Global Status: G5 - Secure
Other Statuses: IUCN Red List Category: LC - Least concern
