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Predation on Waterfowl in Arctic Tundra
and Prairie Breeding Areas: A Review

Status of Population

Most populations of swans and geese in North America have increased or remained stable in recent decades, although many populations experienced severe fluctuations in the past century (emperor geese; cackling, dusky [B. c. occidentalis], and Aleutian [B. c. leucopareia] Canada geese; and brant; Raveling 1984; King and Derksen 1986; Pamplin 1986; Hodges et al. 1996). Less is understood about the status of sea duck populations, but several populations have reached critically low levels (e.g., spectacled [Somateria fisheri] and Steller's [S. stelleri] eiders; see Petersen and Hogan 1996, Hodges et al. 1996). Predation has not been identified as a serious threat overall to populations of swans, geese, and sea ducks. Nevertheless, local populations have occasionally suffered high rates of predation, and the importance of predation in population declines should not be minimized (King and Derksen 1986, Pamplin 1986, Stehn et al. 1993, Sedinger et al. 1994, O'Briain et al. 1998).

Since 1955, duck breeding populations surveyed in the Prairie Region have varied from 34 million in 1956 to 12 million in 1991, when populations of some species were at or near record low levels (Batt et al. 1989, Austin 1998). Since then, populations of most species common in the Prairie Region, except northern pintails and lesser scaup (Aythya affinis), have recovered to levels near or above the population goals of the North American Waterfowl Management Plan (United States Fish and Wildlife Service 1998). Greenwood and Sovada (1996) discussed factors (e.g., drought cycle, habitat conditions, predator populations) contributing to the recovery of duck populations in the 1990s. Population trends among breeding ducks tend to reflect availability of ponds in spring in the Prairie Region (Batt et al. 1989, Austin 1998), but Johnson and Shaffer (1987) presented evidence of long-term population declines in mallards preceding the drought of the 1980s. Bethke and Nudds (1995) indicated that declines in mallards and northern pintails during the recent drought were more severe than predicted on the basis of variation in available wetlands. Furthermore, high predation rates may inhibit the recovery of duck populations when habitat conditions are favorable. Population declines of several species have been linked with low recruitment, primarily attributed to high rates of predation on eggs, but predation on adults and ducklings also have contributed (Cowardin et al. 1985, Klett et al. 1988, Sargeant and Raveling 1992, Greenwood et al. 1995).

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