Density variation and breeding success of the Black Woodpecker Dryocopus martius in relation to forest fragmentation

Abstract

Density of the Black Woodpecker Dryocopus martius was examined and reproductive data collected, both in a forest landscape area (128 km2) and in a farmland area (123 km2 ) with highly fragmented forests (26% forest), in central Sweden during 1985- 1990. The composition, age, and the management practices of the forests did not differ in the two areas. We found that the densities (about 0.15 territorial pairs/km2 of forest land) were the same in the forest area and in the farmland area with highly fragmented forests. Furthermore, we found no differences in the reproductive rate, predation rate, body conditions of the young, or the breeding times between the two areas. The frequency distribution based on the duration in years of the territory occupation was also the same in both areas. We conclude that the Black Woodpecker is not excluded from highly fragmented forests and can successfully breed there, provided that tree composition and food supplies are suitable . However, we do not know what the lower limit of fragmentation is for the species. Further studies of the effects of habitat fragmentation on the Black Woodpecker are needed from northern Fennoscandia, where the density is lower than in southern Sweden.