Factors affecting the distribution pattern of bats in Uppland, central Sweden

Bats were surveyed and insects were trapped in several different habitats to test the hypothesis that insect abundance and types are the most important factors affecting the regional distribution of bats. A bat community of ten species dominated by Eptesicus nilssoni and Pipistrellus pipistrellus was analysed. The results show that the general pattern of bat distribution in different habitats, and the seasonal changes in habitat utilization, could be explained in terms of the abundance of swarming insects, mainly chironomids. Deciduous woodland near water provided essential habitat in early summer for each bat species. Later on, in July, all species spread out to many different habitats. In autumn street-lamps were an important factor affecting bat distribution.