Are the nesting probabilities of the Red-backed Shrike related to proximity to roads?

Abstract

Roads are a pervasive feature in the landscape, and their ecological effects on vertebrate wildlife have been well documented. The main types of effect described are mainly negative consequences on birds and other vertebrates. The major impact of roads on birds includes habitat fragmentation, traffic noise and direct mortality from road kills. However, some passerines, such as the Red-backed Shrike, seem to often use areas close to roads for nesting and hunting purposes. The aim of this paper is to study the importance of road proximity for the selection of suitable shrubs for nesting by the Red-backed Shrike in the farmland landscapes of central Italy. To achieve this goal, the hierarchical partitioning procedures of Generalized Linear Models (GLM) are applied in order to quantify the relative effects of a number of independent variables. At least 77% of the nests we identified were positioned less than 25 meters from roads. The mean distance from the nest to the nearest road was 12.9 ± 18.1 m. The analysis of the relative importance of each variable revealed that "road distance" is one of variables most associated with nesting probability in suitable shrubs. It is reasonable to argue that suitable shrubs and the presence of open spaces for hunting, both of which exist close to countryside roads, might represent the favourable components of the breeding habitat selections of Red-backed Shrikes. Our results can provide useful indications for census techniques and for the planning of conservation measures for the species in agricultural landscapes. Copyright Federico Morelli.