(Currently studied by CWE researcher Matt Evans)
The breeding population of Bufflehead extends across North America's boreal forest and aspen parkland with wintering grounds occurring along both the Pacific and Atlantic coasts. Little is known about exchange between these wintering populations during the breeding season but birds from Alberta are known to migrate to either coast (Gauthier 1993). Birds breeding west and east of Alberta are believed to be philopatric to the Pacific and Atlantic coasts, respectively. No genetic work has been done between the two wintering populations.
Bufflehead are found breeding across boreal North America from interior Alaska to western Quebec, southwards to Wyoming, Oregon, and California (Erskine 1972, Bellrose 1980, Gauthier 1993). Ninety percent of the population is believed to breed from Manitoba westward. Bufflehead are absent from high mountainous areas, preferring elevations between 300-1430m.
Fall migration for birds breeding west of the Rocky Mountains is westward to the Pacific coast travelling through interior British Columbia and the Pacific Northwest, or southward along the Alaskan coastline (Erskine 1972). Birds breeding in the Northwest Territories and east of Alberta migrate east to the Atlantic and south to the Gulf Coast travelling over the Midwest and Great Lakes (Gauthier 1993). Alberta breeders migrate east (47% of band recoveries, n=211), west (35%), and southwest (18%). Birds migrating southwest travel through the Central Flyway (Gauthier 1993). Spring migration routes are the reverse of those in the fall.
Spring and Fall Staging Areas
Little has been documented about the spring and fall staging areas of Bufflehead but they are believed to congregate on large lakes or in major river systems until freeze-up in the fall, or immediately after thaw in the spring (Erskine 1972, Bellrose 1976, Gauthier 1993).
No published information is available for molting areas although in central British Columbia molting birds are being banded on inland ponds of the Chilcotin-Cariboo region (A. Breault and M. Evans, unpublished data). Banding efforts between 1997-2000 indicate large numbers of molting birds, non of which appear to be breeding on these lakes.
Most of the estimated 1.4 million Bufflehead winter along the Atlantic coast from the Maritime provinces south to Mexico. Birds breeding west of the Rocky Mountains winter along the Pacific coast from Alaska to Baja, California (Campbell et al. 1990).
The continent-wide population estimate for 1992 was 1.4 million (Gauthier 1993). Ninety percent of breeding Bufflehead are believed to be located from Manitoba westward. (Gauthier 1993). Although no estimates are provided, highest densities of breeders between 1955-1992 were located in the Athabasca River delta in northern Alberta (Gauthier 1993).
No data is available for staging area abundances. Primary staging areas are still undocumented.
No data is available for molting area abundances. Primary molting areas are still undocumented.
Although no estimates exist, it is believed that most of the estimated 1.4 million Bufflehead winter along the Atlantic coast from the Maritime provinces south to Mexico. Birds breeding west of the Rocky Mountains winter along the Pacific coast from Alaska to Baja, California (Campbell et al. 1990). The most dense Pacific population is thought to be around southern Vancouver Island, British Columbia (Vermeer 1982, Gauthier 1993). Conant (1996) estimated 45,000 birds wintering off the coast of Alaska.
Although no reliable estimates exist, Bufflehead population numbers are generally considered stable or increasing (Gauthier 1993). Bufflehead numbers were severely reduced by over-hunting at the turn of the century (Erskine 1972) but protection under the Migratory Birds Convention between Canada and the United States has allowed steady increases over much of the bird's range. Audubon Christmas Bird Counts between 1927-1966 showed population increases, especially in the east (Erskine 1972). Breeding Waterfowl Surveys between 1955-1992 show Bufflehead increasing at a rate of 13,200 birds/year (p<0.001; Gauthier 1993). However, population declines have been reported in Alaska since 1979 and in the parklands of the Prairie provinces between 1980-1989 (Gauthier 1993).
Bufflehead are a hunted species in their autumn and winter ranges although most harvesting is from inland autumn lakes. Several harvesting estimates exist for different portions of the bird's range. Across the entire range, Bufflehead numbers were severely reduced by over-hunting at the turn of the century (Erskine 1972). Between 1988-1991 the annual harvest in North America averaged 111,084 ± 7,901 birds with 72% of the harvest being in the United States (Martin et al. 1990, 1992, Levesque et al. 1993). This number accounted for 1-2% of all waterfowl harvested in North American during these years (Gauthier 1993). Harvest estimates for British Columbia between 1974-1996 averaged between 2406-2678 birds/year (Lougheed et al. 1996, CWS National Harvest Survey 1996). Estimates from Alaska between 1987-1997 averaged only 291 birds/year (Wentworth 1998).
In general, harvesting rates have declined in Canada since the 1970's and increased only slightly in the United States (particularly in the east).
Management and Conservation Concerns
Concerns for the Bufflehead breeding population relate to the impacts of forest harvesting on the availability of suitable cavity trees for nest sites. Breeding populations are also threatened by agricultural expansion across the prairies. Wintering populations are also vulnerable to coastal petroleum transportation and to the threat of fuel spills.
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Breault, A. Can. Wildl. Ser., Pacific and Yukon Region, Delta, B.C., Can.
Campbell, R.W., N.K. Dawe, D. McTaggart-Cowan, J.M. Cooper, J.W. Kaiser and M.C.E. McNall.1989.The birds of British Columbia. Vol. 1. Non Passerines. Royal British Columbia Museum, Can. Wildl. Serv. 514 pages. Stackpole Books, Harrisburg, PA.
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Martin, E.M., P.I. Padding, and P.H. Geissler. 1992. Preliminary estimates of waterfowl harvest and hunter activity in the United States during the 1991 hunting season. U.S.F.W.S., Laurel, MD.
Vermeer, K.1982.Food and distribution of three Bucephala species in British Columbia waters. Wildfowl 33:22-30.
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U.S.F.W.S., Migratory Bird Management, Anchorage, Alaska.