Forest development phases as an integrating tool to describe habitat preferences of breeding birds in lowland beech forests

Abstract

Land management causes changes in forest structure and thus influences the composition and abundance of communities of forest-inhabiting bird species. However, it is unclear how these changes translate into local habitat suitability for certain bird species given that detailed knowledge on habitat use by forest bird species is still scarce. We have analyzed the habitat preferences of 37 breeding bird species in 19 lowland beech forests, each with an average size of 40 ha. We used Jacobs habitat selection index to quantify preference or avoidance of certain forest developmental phases (fdp). Fdp divide the forest life cycle into different periods, each characterized by a certain combination of habitat parameters (canopy cover, tree dimension, deadwood amount, regeneration cover), thereby integrating several age-specific structural properties. We found that fdp representing the last third of the forest life cycle were significantly preferred by most of the bird species. Of the 37 bird species analyzed, 19 showed the highest preference for the terminal phase or the disintegration phase; this was especially true for hole breeders, semi-hole breeders, ground breeders and beech forest indicator species. Moreover, each bird species showed a characteristic profile of preferred and avoided fdp. Some bird species, such as several free breeders, also preferred younger fdp, such as gaps or regeneration phases. Further, mean fdp patch size turned out to be a strong predictor of bird community composition. Our study confirms that most bird species show a strong preference for later fdp, such as the terminal phase and disintegration phase. However, the simultaneous availability of a mixture of different fdp on local scales meets the habitat preferences of most species and promotes biodiversity of breeding bird communities in lowland beech forests.