Oaks (Quercus sp.) and only oaks? Relations between habitat structure and home range size of the middle spotted woodpecker (Dendrocopos medius).

摘要

The relations between habitat factors and home range size of 33 radio-tracked middle spotted woodpeckers (Dendrocopos medius), an endangered species confined to mature oak forests, were examined during 1992-96 in northern Switzerland. Stepwise backward multiple regression revealed that home range size decreased from winter to late spring; furthermore, range size was inversely correlated to the densities of large oaks (>=36 cm dbh) and of potential oak cavity trees. Neither intra- nor interspecific competition seemed to influence home range size. Jackknife and cross-validation procedures indicated good predictive capability of the habitat model. Therefore, both the availability of large oaks, being related to potential food abundance, and of potential cavity trees, being related to reproduction, appear to be used as proximate cues to determine home range size. Management decisions concerning the endangered middle spotted woodpecker have focused on the conservation and promotion of large oaks; in the future they should consider the supply of trees suited for cavity excavation as well.