Effects of food supplementation on depredation of duck nests in prairies by striped skunks
We examined provision of supplemental food as a method for reducing depredation of upland-duck nests, especially by striped skunks (Mephitis mephitis). Predators negatively influence duck recruitment in grassland ecosystems. Managers are in search of methods, particularly nonlethal methods, for reducing nest depredation. We conducted this study on 24 areas managed for wildlife production in the Prairie Pothole Region of central North Dakota during 1993-1994. We provided a mix of fish offal and sunflower seeds on 12 areas; no food was provided on the remaining 12 control areas. Although we observed a tendency during both years for higher nest success rates on provisioned areas ( = 46%, 1993; 36%, 1994) than on control areas ( = 27%, 1993; 31%, 1994), mean nest success rates (Mayfield 1961) overall did not differ significantly between food-provisioned areas ( = 41%) and control areas ( = 29%). Striped skunk depredation rate was lower on food-provisioned areas (11%) than on control areas (24%), suggesting that skunks reduced their consumption of eggs when provided with a food supplement. In 1994, habitat conditions were optimal, and ducks nested persistently into the summer when nest success rates of food-provisioned areas and control areas differed by only 5 percentage points. That year American badgers (Taxidea taxus) and Franklin's ground squirrels (Spermophilus franklinii) apparently compensated for reduced depredation by skunks. Thus, although skunks and other mammalian predators seem to have responded positively to food provisioning, nest depredations overall did not change. Provision of supplemental food apparently has limited value for managing depredation of upland duck nests in the Prairie Pothole Region where predator communities are complex.