Predator‐avoidance behaviour in a nocturnal petrel exposed to a novel predator

Many species of bird recognize acoustic and visual cues given by their predators and have complex defence adaptations to reduce predation risk. Recognition of threats posed by specific predators and specialized anti‐predation behaviours are common. In this study we investigated predator recognition and anti‐predation behaviours in a pelagic seabird, L each's S torm‐petrel O ceanodroma leucorhoa , at a site where predation risk from G reat S kuas S tercorarius skua is exceptionally high. Leach's Storm‐petrels breed in burrows and come on land only at night. Counter‐predator adaptations were investigated correlatively in relation to changing natural light levels at night, and experimentally in relation to nocturnal visual and acoustic signals from G reat S kuas. Colony attendance by L each's Storm‐petrels was attuned to changes in light conditions at night and was highest when nights were darkest. This behaviour is likely to reduce predation risk on land; however, specific recognition of G reat S kuas and specialized defence behaviours were not found. L each's Storm‐petrels, in particular apparently non‐breeding individuals, were entirely naïve to the threat posed by G reat S kuas and were captured easily in a variety of different ways, on the ground and in the air. Lack of specialized behavioural adaptations in L each's Storm‐petrels against G reat S kuas may be because spatial overlap of breeding distributions of these species appears to be a rare and recent phenomenon.