GJERDE I, ROLSTAD J & WEGGE P (1997) Dutch Ornithological Union: Theme Day Effects of habitat fragmentation on birds and mammals: Effects of habitat fragmentation in the boreal forest on resident bird species with mediumsized home ranges. LIMOSA 70 (1): 36-36.

Although most land area in the boreal zone is covered by forest, the preferred habitats of several forest species are highly fragmented. Among birds the resident species seem to be most vulnerable to habitat fragmentation (Fig. I). Populations of old forest species like the Capercaillie Tetrao urogallus and species dependent on insects in dead wood like the White-backed Woodpecker Dendrocopos leucotos may be seriously affected by the changes in forest structure caused by forestry. Due to their medium-sized home ranges (c.100 ha) the density of these species are also affected by the mosaic patterns of habitats in Scandinavian forests. Norwegian studies indicated that individual birds responded to fragmentation by enlarging their home ranges. However, the enlargement of home range was accompanied by an increased winter and spring mortality. The most important impact on the population dynamics of Capercaillie, however, was through an increased predation rate on nests and chicks. In Capercaillie fragmentation of traditional lekking sites resulted in a dispersed pattern of displaying males and a more even distribution of matings among them.
      A reduction in population size caused by reduction in habitat area is evident in both Capercaillie and woodpeckers. However, the woodpeckers seem to be less vulnerable to isolation and less negatively affected by the surrounding matrix than the Capercaillie. In western Norway the density of White-backed Woodpecker per area habitat was similar to the density reported from Bialowieza (Poland), although the scattered habitat patches in Norway constituted less than 10% of the area compared to 64% in Poland.

[free pdf] [dutch summary]