Nest site selection in Norwegian woodpeckers

Abstract

The nest site selection of seven Norwegian woodpeckers, Dryocopus martius, Picus viridis, P. canus, Picoides tridactylus, Dendrocopos leucotos, D. major and D. minor, was compared. The following parameters were measured at the nesting tree: forest type, tree species, the tree's “degree of decay”, the height of the tree, the hole's height above the ground, the stem's diameter at the hole and 0.5 m above the ground, earlier holes in the stem, and whether the tree was broken or not. Several differences between species were found in forest type and tree species. The use of weakened and dead nesting trees tended to increase with decreasing size of the bird. The following parameters usually decreased with decreasing size of the species: the height of the tree and of the nesting hole, and the stem's diameter at the hole and near the ground. Overlap in nest site parameters was calculated for four species, D. martius, P. viridis, D. major and D. minor, common nesters in Populus tremula. Overlap between D. minor and the other three species was low, whereas considerable overlap was found between D. martius and P. viridis. Both species prefer large, old Populus tremula trees.