Climate and habitat influence nest predation by snakes on cavity-nesting birds

Abstract

Snake predation is a major cause of avian breeding failure, particularly for cavity breeders, for which snakes may be the primary predators. We analysed 141 inferred snake predation events from 846 breeding events over 8 years in nest boxes used by the oriental tit (Parus minor) and the varied tit (Sittiparus varius). Using principal component analysis and Cox proportional hazard models, we identified factors affecting snake predation risk. Predation on eggs increased during the late, warmer part of the breeding season, with an interactive weather effect: risk increased on sunnier days early in the cool season, but on rainier days late in the warm season. For oriental tit nestlings, predation risk was affected primarily by temperature and breeding date, whereas varied tit nestling predation was driven by habitat and nestling age, with the highest risk being for younger nestlings in natural forests. These interspecific differences might be linked to breeding phenology and species-specific habitat associations. The effect of nestling age might relate to snake gape-size limitation. Our findings suggest that under climate change, snake predation risk might vary regionally, depending on temperature-rainfall interactions, whereas habitat characteristics and breeding ecology might more strongly shape species-specific predation patterns.