Predator removal and nesting waterbird success at San Francisco Bay, California

The efficacy of long-term predator removal in urbanized areas is poorly understood. The impact of predation on ground-nesting waterbirds, as well as predator abundance and composition in predator removal versus non-removal or reference sites were examined at South San Francisco Bay. The success of natural nests and predator activity was monitored using track plates, trip cameras, wire haircatchers and simulated nests. Removal sites had higher nest densities, but lower hatching success than reference sites. Predator composition and abundance were not different at the removal and reference sites for any predator other than feral Cat (Felis domesticus). Striped Skunk (Mephitis mephitis) comprised the majority (84%) of predators removed, yet remained the most abundant predators in removal and reference sites. Urban environments provide supplemental food that may influence skunks and other nest predators to immigrate into vacancies created by predator removal. Based on the findings from this study, predator removal should be applied intensively over a larger geographic area in order to be a viable management strategy for some mammalian species in urbanized areas.