Effects of removing duck-nest predators on nesting success of grassland songbirds

Abstract

During 1995 and 1996 we monitored natural and simulated nests of grassland songbirds following removal of duck-nest predators, primarily raccoons (Procyon lotor), striped skunks (Mephitis mephitis), and red foxes (Vulpes vulpes), in North Dakota, U.S.A. We were unable to detect an effect of predator removal on survival of natural (n = 153 nests) or simulated (n = 2264 nests) nests of grassland songbirds in either year. However, the assemblage of predators destroying simulated nests differed between removal and non-removal sites in 1995, when medium-sized carnivores and small mammals were the most important predators on non-removal sites, whereas ground squirrels were most important on removal sites. Our study indicates that grassland songbirds were not negatively affected, at least in the short term, by removal of duck nest predators. However, changes in the relative importance of predators on removal sites in 1995 suggest that smaller predators that were not targeted by removal efforts (i.e., ground squirrels) may have caused compensatory predation. Long-term studies are necessary to determine if the removal of duck-nest predators affects the numerical or functional response of predators at a lower trophic level, such as ground squirrels and other small mammals.