Coarse landscape features predict occurrence, but habitat selection is driven by specific habitat traits: implications for the conservation of the threatened Woodchat Shrike Lanius senator

Abstract

SummaryHabitat selection has fundamental implications for species conservation, and in birds is often regarded as a multi-scale process. We investigated (under an information-theoretic approach) habitat selection by Woodchat Shrike Lanius senator in Italy (one of the most severely declining species in central and western Europe), considering five main types of potential determinants of shrike occurrence at the territory scale (1 ha): general structure (coarse landscape), woody vegetation, grassland habitats/bare ground, herbaceous crops, and management variables. The best supported models for species occurrence were those including general structure and woody vegetation traits. Variation partitioning suggested that overall, landscape general structure and woody vegetation explained the highest variation in shrike occurrence, and management the lowest. However, considering variation explained by only a single level, all levels performed nearly equally, but general structure did not explain an exclusive proportion of variation. A multi-level analysis suggested that shrike occurrence was eventually associated with specific habitat traits: isolated trees, shrubland and (secondarily) olive groves (all with positive effects), and dirt roads (negative effect). The most parsimonious multi-level models included only variables from woody vegetation and management traits, suggesting that the likely true determinants of species occurrence are highly specific and fine-scale habitat traits, consistent with variation partitioning. Woodchat Shrikes inhabit semi-open landscapes, within which they are attracted to shrubland and isolated trees (secondarily to olive groves) and avoid dirt roads. Suitable habitat conditions for the species depend on a trade-off between abandonment and intensive farming, and rural development programmes may be crucial for the conservation (or loss) of such conditions.