Weather and predation pressure: the case of the Red-backed Shrike (Lanius collurio)

Abstract

Breeding success in birds is closely dependent on predation: although this behaviour can be modified by the weather, its mechanisms are not well understood. Analysis of the breeding success of Red-backed Shrikes (Lanius collurio) in eastern Poland, which has a temperate transitional climate, showed that predation did indeed increase significantly during periods of prolonged rainfall, but that air temperature and wind speed did not affect predation significantly. As insects become less active during rainy weather, predators like Magpies (Pica pica) and Jays (Garrulus glandarius), which frequently consume such prey, then have to switch to birds’ eggs and nestlings as sources of food. In recent years, less rain has been falling in this part of Poland in the summer, so one can anticipate a higher level of breeding success in the red-backed shrike, on condition that the numbers of potential predators do not increase equally quickly.