Nest predators affect spatial dynamics of breeding red-backed shrikes (Lanius collurio)

Abstract

1. Predation may be a strong selective factor affecting individual behaviour and life histories. However, few studies have investigated whether predators affect breeding habitat selection of prey species. 2. We tested whether breeding habitat selection and reproduction of a tropical migrant, the red-backed shrike (Lanius collurio L.), was related to the presence of breeding pairs of its potential nest predators, magpie (Picapica L.), hooded crow (Corvus corone cornix L.) and jackdaw (C. monedula L.). 3. Only magpie and hooded crow territories were associated with an elevated risk of predation based on an artificial nest experiment with nests mimicking red-backed shrike nests. Predation risk on real red-backed shrike nests was also higher close to nests of hooded crow and magpie than elsewhere in the landscape. 4. Occupation frequency of known red-backed shrike territory sites during 3 years of study increased with increasing mean distance to the nearest magpie nest. 5. Changes in spatial distribution of corvids affected the spatial distribution of red-backed shrikes. Vacant red-backed shrike territory sites were more likely to become occupied in the next year when magpie and hooded crows had moved away from the site, while occupied sites were more likely to be abandoned in the next year when at least hooded crows had moved closer. 6. Our results suggest that breeding territories of nest predators may affect breeding habitat selection of prey species. Thus, a large part of an observed spatial dynamics of prey species may be caused by a corresponding spatial dynamics of predators. Because sink territories are occupied more irregularly than source territories, we suggest that the dynamics in predator sinks may be the driving force of the spatial dynamics of prey species.