Video monitoring of shrub-nests reveals nest predators

Abstract

Capsule: Jays Garrulus glandarius are the most common predators, but carnivorous mammals and some other species also predate nests. Aim: To uncover the mechanisms and consequences of nest predation. Methods: I used video-recording equipment to record the fates of 132 nests of Blackcap Sylvia atricapilla over a three-year period. An additional 69 nests without video-recording equipment were monitored for comparison. Results: I found a total of 11 species depredating eggs and young of Blackcap. The main predator was Jay, which hunted during the day and was responsible for 21% of nest fates and 46% of nest losses. Many other predators were recorded, mainly carnivorous mammals (Stone Marten Martes foina, Red Fox Vulpes vulpes, Least Weasel Mustela nivalis), which hunted from dusk until dawn and accounted for 25% of nest losses. Wild Boar Sus scrofa and Tawny Owl Strix aluco also predated nests. Whereas mammals needed up to 15 minutes at a nest to consume nest contents, Jays stayed only a few seconds to remove eggs or young, often taking them one by one. When scared off, adults returned to the nest within 15 minutes. Nests were abandoned if only one egg or no young were left and the adults spent up to nine hours and 12 visits before abandoning the nest completely. The overall impact of the video equipment on nest success was low. Conclusion: This study underlines the potential of video recording in science and management and the method is recommended for studies on other open-cup-nesting songbirds.