Assessing the presence and species richness of owls and woodpeckers through bioacoustics in two differently managed Alpine forests

Birds present large differences in species-specific responses to forest features such as structure and composition, and therefore they act as an indicator of forest ecosystem biodiversity. Woodpeckers and owls, specifically, are considered important forest naturalness indicators and their presence reflects those of numerous other forestdwelling species. Because of their habits and behaviour, they are more difficult to detect than the passerine species, and therefore the implementation of the bioacoustics discipline is suited to the survey of such taxa. In the present study we collected data about the presence and species richness of owls and woodpeckers in relation to the main forest structure and composition variables (basal area, dominant height, tree species diversity, living trees’ vegetational conditions, canopy closure percentage, total deadwood volume, decomposition stage) in two forest sites which share similar ecological characteristics, but differ in terms of management: Cajada (non-intensively managed) and Tovanella (abandoned). Both Cajada and Tovanella forests report the presence of bird species belonging to the taxa of woodpeckers and owls, which are indicators of the forest at late-successional stages. In Cajada we contacted woodpeckers and owls a significantly higher number of times than in Tovanella, and the decomposition stage of deadwood and the level of canopy closure seem to the main explanatory factors of such results. Since management practices in Tovanella have been only recently abandoned we think that our results might change in the future. Therefore, further research is needed, also to better assess how sustainable forest management might conserve key forest features which are crucial for the thriving of most demanding owls and woodpeckers.