Bird Numbers across Edges between Mature Conifer Forest and Clearcuts in Central Sweden

Abstract

Bird distributions were examined along transects extending from forest edges 250 m out on clearcuts and the same distance inside forests. Inventories were performed in spring, summer and autumn 1980, winter 1980/81 and spring 1981. 67% of all observations were made in forest parts. However, there was a seasonal change with relatively more observations on clearcuts in summer and autumn. There were considerably more observations and higher densities in an outer forest belt of c. 50 m than deeper inside the forest. This was apparent for most species but particularly in the common species Erithacus rubecula, Fringilla coelebs and certain Parus spp. There were few pronounced edge species (Anthus trivialis and Parus major dominating in numbers). Fewer individuals of open land species were observed in the first 100 m of clearcuts than in their centres. There the bird fauna differed completely from that in the forest, consisting of just a few species of open habitats, such as Emberiza citrinella and Lanius collurio. The high occurrence of tree-gleaning species in the outer forest belt is suggested to depend on a rich supply of insects. The low density of open land species on clearcuts close to the forest may be due to several factors generally important on habitat islands as varying intraand interspecific competition and risks for ambush predation.