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

Abstract

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,Leach'sStorm‐petrelOceanodroma leucorhoa, at a site where predation risk fromGreatSkuasStercorarius skuais 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 fromGreatSkuas. Colony attendance byLeach'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 ofGreatSkuas and specialized defence behaviours were not found.Leach's Storm‐petrels, in particular apparently non‐breeding individuals, were entirely naïve to the threat posed byGreatSkuas and were captured easily in a variety of different ways, on the ground and in the air. Lack of specialized behavioural adaptations inLeach's Storm‐petrels againstGreatSkuas may be because spatial overlap of breeding distributions of these species appears to be a rare and recent phenomenon.