Spatial ecology of breeding birds in forest landscapes: an indicator species approach

Abstract

Indicator species have been proposed to reveal common status of ecosystems and their biodiversity. In this thesis, forest bird species were studied based on territory and nest site mappings within a forest-dominated landscape in southern Finland. The general aims of the thesis was to find candidates of indicator bird species that would predict general variation in species richness and density of forest bird assemblages, to reveal more exactly species with indicator property at multiple spatial scales, and to study factors that affect occurrence and dynamics of indicator species in forest landscapes. The potential indicator species were screened by evaluating statistical models. The redbreasted flycatcher (Ficedula parva Bechst.), the pygmy owl (Glaucidium passerinum L.) and the three-toed woodpecker (Picoides tridactylus L.) were found to be the most suitable candidates of multiscale indicators of forest bird species richness. In general, models with small spatial scale and several indicator species were observed to better explain the total variation in species richness. The results show that a carefully selected set of bird indicator species may be useful and efficient method for evaluation of forest bird diversity. The densities of the above-mentioned three species were also higher in the surroundings of capercaillie (Tetrao urogallus L.) leks where also the overall species richness of forest birds was higher. The density of capercaillie also coincides with general wildlife richness. Capercaillie can thus be considered a good candidate for an umbrella species for wildlife. The occurrence of the three-toed woodpecker was influenced by spatial dynamics of the species and the quality of the landscape. Territory quality of three-toed woodpecker may, however, be substantially modified by species interactions and be mediated to its population development. The results suggest the presence of quality threshold values of forest environment, which may determine the occurrence of the three-toed woodpecker and similar species in forest landscapes.