Abstract
The aim of this project is to study forestry-induced cascading effects on the interaction of epiphytic lichens, invertebrates and birds. There is a strong correlation between abundance of epiphytic lichens and abundance of invertebrates in boreal forests. However, many epiphytic lichens have declined drastically due to forestry. The same pattern is found for some non-migratory birds, e.g. tits. My hypothesis is that high invertebrate abundance mediated by high lichen biomass is critical to non-migratory passerines during winter, when food is scarce and energy needs high. This will be tested by comparing bird-mediated giving up densities (GUD:s) of invertebrates in bird territories located in lichen-rich forests and lichen-poor forests. The magnitude of the GUD will be used as an indirect measure of the territory's quality, since theory predicts that a food patch should be abandoned when its food density equals the average food abundance in the habitat. The experiment will be complemented with focal sampling of the tits foraging behaviour. Further, considering the large structural differences among species of epiphytic lichens, different species probably provide separate habitats to invertebrates. In light of that some lichen species have declined recently due to forestry, species composition of lichens will be related to species composition of invertebrates. The proposed research will be especially relevant for conservation of biodiversity in boreal coniferous forests.
Sweden