Nest site selection in Norwegian woodpeckers

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