Abundance of two threatened woodpecker species in relation to the proportion of spruce plantations in native pine forests of western Norway

In a comparative study we investigated woodpecker abundance in forest landscapes with different proportion of native pine forest and spruce plantations in western Norway. In 100 circular study plots of 100 ha each we recorded 38 white- backed - Dendrocopos leucotos, 22 grey- headed - Picus canus, 13 great spotted - Dendrocopos major, 6 green - Picus viridis, and 2 lesser spotted - Dendrocopos minor woodpeckers in the breeding season. The mean number of recorded woodpecker species peaked at 20 - 40% spruce plantations. The two most common species in the study, the white- backed and the grey- headed woodpeckers are both Red-listed species in Norway and among the rarest woodpeckers in Europe. The white- backed woodpecker preferred plots with higher than average proportions of standing dead trees and deciduous trees, and low proportions of spruce plantations in the plots. The grey-headed woodpecker preferred plots in the western ( coastal) parts of the study area with presence of large aspen Populus tremula trees. Logistic regression models did not reveal any clear threshold values with respect to proportion of spruce plantations in plots, although both woodpecker species were extremely rare in plots with > 60% spruce plantations. We recommend spruce plantations to be kept at moderate levels to ensure viable populations of woodpeckers in western Norway.