Does nest site availability limit populations of secondary cavity-nesting birds in Quercus pyrenaica forest?:an experimental approach

Abstract

Resumo alargado disponível em português

Tree cavities, potential nest sites, may act as a limiting resource for populations of secondary cavity-nesting (SCN) species. We examined the response of an assemblage of SCN birds, in forests of Pyrenean Oak (Q. pyrenaica), NW of Spain, to the first experiment of both increment and reduction of nest site availability, with a replicated before-after-control experimental design ever tried. Nest density increased significantly with the addition of nest-boxes by 40% and decreased also significantly with cavity blocking by 57% during the post-treatment period (2008), compared to pre-treatment period (2007). Nests of 8 SCN were recorded: Green Woodpecker, Eurasian Nuthatch, Short-toed Treecreeper, Great Tit, Blue Tit, Spotless Starling, Pied Flycatcher and Common Redstart. Cavity suitability index based on pre-treatment occupation also declined significantly along with the cavity blocking experiment. Moreover, reused cavities had a higher suitability index than those cavities used only once. The results support the hypothesis that the assemblage of SCNs in Pyrenean Oak forests is limited by the availability of suitable nest-sites