DECIDUOUS FOREST AND RESIDENT BIRDS - THE PROBLEM OF FRAGMENTATION WITHIN A CONIFEROUS FOREST LANDSCAPE

Six species of resident birds were censused in patches of deciduous fo rest within a coniferous forest landscape in south central Sweden. Her e, the forests have been subjected to active forestry for a long time, but with recently increased intensity. Although the forest cover is m ore or less continuous in this landscape, mature deciduous forest is n ow a rare element compared with the untouched forest. All censused pat ches were similar with regards to size, proportion and amount of decid uous trees, but were either isolated in the coniferous forest ('isolat ed patches') or near to other deciduous patches ('aggregated patches') . We concentrated on six species of resident birds, with moderate area requirements, that are tied to deciduous forest and whose ecology is well-known. The Nuthatch and the Marsh tit, which both show strict yea r-round territoriality and have a restricted dispersal phase, were sig nificantly more likely to be found in aggregated than in isolated patc hes. No effect was found for the Great tit and the Blue tit, which are less territorial outside the breeding season and have a longer disper sal phase. Moreover, the Great tit is less specialized on deciduous fo rest than the other species, Also, the Long-tailed tit was negatively affected by isolation, which may be due to restricted dispersal and to larger area requirements of this flock-territorial species. The Hazel grouse, finally, was not affected, but this larger bird probably uses the forest in a different way from the smaller species. Our study cle arly shows that fragmentation of one type of forest (deciduous) within another can have serious detrimental effects on forest-living species and raises important issues for forest management practices and conse rvation within a forest landscape.