Nest survival and cause-specific nest mortality in the San Clemente Bell’s Sparrow

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Nest monitoring and the use of camera systems can provide researchers with reproductive data integral to the successful management and recovery of threatened and endangered avian species. From 2012 to 2019, we used cameras to monitor 110 nests of the threatened San Clemente Bell’s Sparrow (<i>Artemisiospiza belli clementeae</i>) to identify nest predators and evaluate threats to their recovery on San Clemente Island (SCI). We evaluated the effects of winter precipitation, nest initiation date, and nest substrate on nest survival rates. We also used cameras to identify and estimate cause-specific mortality rates from native and non-native nest predators. We did not observe significant impacts of precipitation or nest initiation date on nest survival. Nests in California boxthorn (<i>Lycium californicum</i>) had significantly lower survival rates than nests in other substrates. The native San Clemente Island fox (<i>Urocyon littoralis clementae</i>) was the most common nest predator, followed by non-native black rats (<i>Rattus rattus</i>). Overall, nests were much more likely to be predated by native than non-native predators. This suggests that San Clemente Bell’s Sparrows could achieve recovery despite the presence of non-native predators. Our findings help describe and quantify the breeding ecology of San Clemente Bell’s Sparrows, providing necessary information for data-driven management and recovery efforts.