Use of sensory cues by fish crows Corvus ossifragus preying on artificial bird nests

Abstract

How predators locate avian nests is poorly understood and has been subjected to little experimental inquiry. We examined which sensory stimuli were important in the nest‐finding behavior of fish crows Corvus ossifragus, a common nest predator in the southeastern United States. Using an array of potted trees in a large enclosure, we presented artificial nests to captive crows and quantified responses to visual, auditory, and olfactory nest cues, and nest position. Partial ranks of nest‐treatment preferences were analyzed using log‐linear models. Nest visibility significantly increased the likelihood of predation by fish crows and increasing nest height was a marginally significant influence on nest vulnerability; no responses were apparent to auditory or olfactory stimuli. Our findings demonstrate that fish crows are visually‐oriented nest predators that may preferentially prey on, or more readily encounter, above‐ground nests. Moreover, the experimental design provides a new method for evaluating predator‐prey interactions between nests and their predators. This study also illustrates how sensory capabilities of predators can interact with nest types to determine nest predation patterns.