Occurrence of the Lesser Spotted Woodpecker Dendrocopos minor in relation to area of deciduous forest

Abstract

In the springs of 1985 to 1988, amateur ornithologists searched for Lesser Spotted Woodpeckers in 152 census areas in the south and central parts of Sweden. Each census area was 200 ha. The frequency of occurrence of the woodpecker increased with the total area of deciduous woodland; when the census areas contained less than 17 ha, it was 24%, when the areas had 17-38 ha it was 62%, and with >38 ha deciduous woodland it was 80%. The latitude in south and central Sweden had no significant effect on the area requirement, but our results show that the species requires larger areas in managed than in natural forests. A stepwise discriminant analysis revealed that the occupation of census areas by the Lesser Spotted Woodpecker could be predicted with 68% accuracy from the area of nemoral and riparian deciduous woods (positive association with occupation) and the area of mixed coniferous/deciduous wood (negative association with occupation). Non-nemoral deciduous wood, marsh wood, stand age and the density of snags did not enter the discriminant function . The area of nemoral deciduous forest has decreased in Sweden during the second half of this century due to cutting. This is probably one cause of the decline of the Lesser Spotted Woodpecker.