Meta-analysis of predator identity in nest-camera studies in the British Islands

Abstract

Nest predation is the primary cause of nest failure across many bird species. Interventions to support declining or threatened species frequently involve measures to reduce nest predation, through lethal control or non-lethal methods. However, their efficacy relies on a robust understanding of predator identity. The development of unobtrusive, infrared digital video surveillance now allows the identity of nest predators to be confirmed directly. Here, we collate and analyse nest-camera studies from England, Wales, Scotland and the Isle of Man, which are dominated by anthropogenic landscapes and lack most apex predators, but have a high abundance of mesopredators. We quantify the contribution of predator class and functional groups across groups of prey species, nesting habitats or nest strata. For quantitative analysis we collated 46 nest predation studies, comprising 2088 nests and 609 predation events across 24 avian prey species. Nest predation studies are not yet representative, mostly comprising waders (Charadriiformes) and a few passerines, in grassland and woodland habitats, respectively, with farmland and urban habitats poorly sampled. Wader clutches were predominantly predated by mammals (primarily European Badger Meles meles and Red Fox Vulpes vulpes and, particularly on islands, European Hedgehog Erinaceus europaeus; together 53% of events), but with non-trivial contributions by ungulates (6%), predominantly Sheep Ovis aries. For passerines, clutches were predated by corvids (31% of events) and mammals (primarily Badger, Hedgehog and Fox, 25% combined). Compared with depredation of passerine clutches, passerine broods were taken by a wider range of predators, particularly avian predators, predominantly Eurasian Jay Garrulus glandarius (23% of events, though noting 73% of songbird predation events were in woodland) and raptors (21%), but also reptiles. Despite the attention given to impacts of Grey Squirrel Sciurus carolinensis, its contribution to observed nest predation was negligible. Further work is required to expand understanding of nest predator identity, to improve understanding of changing predator influences across populations, so that, where appropriate for conservation, management strategies can be better informed.