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Waterfowl Remains at Dens

Remains of 1,857 adult ducks were identified from 1,432 red fox rearing dens visited. Eighty percent of the dens and 96% of the ducks were from North Dakota and South Dakota (Fig. 1, Table 1). We believe that in all areas except Nebraska nearly all ducks found at dens were from breeding populations. The low numbers of wintering ducks in the northern twothirds of the midcontinent area coupled with high food demands of foxes and other scavengers of duck carcasses during winter almost precluded the possibility of significant numbers of fall carrion ducks being available to foxes in spring. Most ducks found at the Nebraska dens were probably from migrating and wintering populations and many may have been scavenged. Most dens visited in Nebraska were from the vicinity of the Platte River, a wintering area for mallards and a migrational staging area for many duck species (Jorde 1981).

In addition to adult ducks, other waterfowl found at the dens were 8 ducklings and 11 geese. The low number of ducklings has little meaning because nearly all ducklings brought to dens are totally consumed by fox pups (Sergeant 1978). The low incidence of geese reflects their large size and low availability to foxes during the spring migration and nesting season. Relatively few geese nested in the midcontinent area and those that did were at scattered locations.