Landscape structure influencing the spatial distribution of the Short-toed Treecreeper Certhia brachydactyla in a Mediterranean agroecosystem

Abstract

The Short-toed Treecreeper Certhia brachydactyla is a sedentary passerine species, considered a typical woodland species and an ecological indicator of forest alteration and fragmentation. The aim of the research was to define the habitat selection of the Short-toed Treecreeper during the breeding season in a Mediterranean landscape with scarce and highly altered woodland cover. The study was carried out in southern Italy, where point counts were made between April and May in the 2012 and 2013 breeding seasons. The habitat suitability was evaluated following a use vs availability approach, investigating the effect of arboreal habitats, such as woodlands, orchards, and olive groves, at the presence sites and in the surrounding landscape. A resource selection probability function was formulated, performing a logistic regression analysis with binomial error distribution. Model selection followed an information-theoretic approach using the AICc. The best model showed that the most important variables positively affecting the species were percent cover of orchards and olive groves within 750 m of the presence sites, as well as the number of patches of olive groves and woodlands within 250 m. The results showed that olive groves and orchards could be supplementary habitats for the Short-toed Treecreeper when woodlands were absent. Furthermore, the results suggest a primary influence of habitat fragmentation in the population dynamics which lead to Short-toed Treecreeper occurrence, even in a Mediterranean setting.