Indicators of forest biodiversity: which bird species predict high breeding bird assemblage diversity in boreal forests at multiple spatial scales?

Indicator species have been proposed to be used for revealing common status of ecosystems and their biodiversity. We studied breeding forest birds in southern Finland. Our aim was to find bird species combinations that would predict species richness of forest bird assemblages at several spatial scales. We evaluated statistical models that included 1-5 indicator candidate species, and ranked them according to the Bayesian information criterion. The red-breasted flycatcher Ficedula parva, the pygmy owl Glaucidium passerinum and the three-toed woodpecker Picoides tridactylus were found to be the best multiscale indicators. Models at smaller spatial scales, including several indicator species better explained the total variation in species richness. The indicators mostly revealed properties of the forest site rather than variation in species richness caused by species interactions. Our results show that a suitable set of indicator species may be a useful and quick method for the evaluation of bird diversity in forest environments.