The importance of key marginal habitat features for birds in farmland: an assessment of habitat preferences of Red-backed Shrikes Lanius collurio in the Italian Alps

Key marginal habitat features maintain their importance even when they occur at very low density. Aims To assess the importance for breeding birds of key habitat elements, such as isolated shrubs, hedgerows and untilled vegetation patches. Methods We investigated the habitat preferences of Red-backed Shrikes Lanius collurio in an agricultural environment where key habitat elements have been dramatically reduced. Based upon data from territorial maps, a fine-scale model of habitat preference was developed and the results of three different analytical approaches (binary logistic regression, multimodel inference and hierarchical partitioning) were compared. Results The occurrence of Red-backed Shrikes was positively influenced by the extent of non-grazed/mown grassland, isolated bushes and hedgerows, and negatively influenced by woodland cover. The model high-lighted the importance of bushes/hedgerows despite their very scarce occurrence in the study areas (overall, average cover only 7.94%). Breeding densities were rather low, but mean densities were slightly higher in pasture zones in which bushes/hedgerows availability was higher than elsewhere. Conclusion These results confirm the crucial importance of these key marginal elements even in depauperated farmland landscapes. Maintaining and increasing their availability is a key management option for the encouragement of breeding Red-backed Shrikes, and potentially for other species which are also declining in these farmland habitats.