Bird species in Mediterranean pine plantations exhibit different characteristics to those in natural reforested woodlands

Abstract

Passive woodland regeneration following cropland abandonment and pine plantations are two major approaches for vegetation restoration in agricultural landscapes in the Mediterranean Basin. We compared the effects of these two contrasting approaches on local bird density in central Spain on the basis of species characteristics, including regional density, habitat breadth, life-history traits and plumage colouration. Local bird density increased with regional density and habitat breadth in both woodland and pine plantation plots following macroecological patterns of bird abundance and distribution. In woodlands, dichromatic species were more abundant than monochromatic species and bird density increased with the intensity of territory defense and as the proportion of plumage colour generated by pheomelanin decreased. Contrary to our prediction, this latter observation suggests that woodlands may induce higher levels of physiological stress in birds than pine plantations even though these represent a novel habitat change. In pine plantations, sedentary species were more abundant than migratory species and bird density was negatively related to body and egg mass. These traits of bird species in pine plantations are characteristic of successful invaders. The variation in bird density explained by phylogeny was twice as high in pine plantations as in woodlands, suggesting that pine plantations limit accessibility to some clades. Our results support, from an evolutionary perspective, the described inability of pine plantations on cropland to maintain or increase bird diversity in Mediterranean agricultural landscapes.