Characteristics and utilization of old Black Woodpecker Dryocopus martius holes by hole‐nesting species

Old nest holes made by the Black Woodpecker Dryocopus martius were examined in two study areas in Sweden. We found a large variation in nest hole characteristics and that the height in the tree and depth of the hole were important factors in the choice of nest hole by secondary hole nesters. A large proportion of old nest holes remained unoccupied. Many holes were probably of poor quality due to shallow depth, low height or narrow entrance. Nest holes in the vicinity of farmland (<200 m from the field‐forest edge) were more often occupied than nest holes deeper into the forest. This was because Jackdaws Corvus monedula , the numerically dominant species, only used nest holes near farmland. Jackdaws usually used the best nest holes, while other subordinate species had to use inferior holes near fields or nest holes in areas with less competition, deeper in the forest. Besides birds, some mammals and bees were found using old Black Woodpecker holes.