EFFECTS OF FOOD SUPPLEMENTATION ON DEPREDATION OF DUCK NESTS IN UPLAND HABITAT

We examined provision of supplemental food as a method for reducing de predation of upland-duck nests, especially by striped skunks (Mephitis mephitis). Predators negatively influence duck recruitment in grassla nd ecosystems. Managers are in search of methods, particularly nonleth al 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 o ffal and sunflower seeds on 12 areas; no food was provided on the rema ining 12 control areas. Although we observed a tendency during both re ars for higher nest success rates on provisioned areas ((x) over bar = 46%, 1993; 36%, 1994) than on control areas ((x) over bar = 27%, 1993 ; 31%, 1994), mean nest success rates (Mayfield 1961) overall did not differ significantly between food-provisioned areas ((x) over bar = 41 %) and control areas ((x) over bar = 29%). Striped skunk depredation r ate was lower on food-provisioned areas (11%) than on control areas (2 4%), suggesting that skunks reduced their consumption of eggs when pro vided with a food supplement. In 1994, habitat conditions were optimal , and ducks nested persistently into the summer when nest success rate s of food-provisioned areas and control areas differed by only 5 perce ntage points. That year American badgers (Taxidea taxus) and Franklin' s ground squirrels (Spermophilus franklinii) apparently compensated fo r reduced depredation by skunks. Thus, although skunks and other mamma lian predators seem to have responded positively to food provisioning, nest depredations overall did not change. Provision of supplemental f ood apparently has limited value for managing depredation of upland du ck nests in the Prairie Pothole Region where predator communities are complex.