Keystone role of Eurasian beaver Castor fiber in creating the suitable habitat over the core breeding range for forest specialist species the three-toed woodpecker Picoides tridactylus

Abstract

The European breeding range of the three-toed woodpecker Picoides tridactylus overlaps with the distribution range of coniferous and mixed forests with domination of Norway spruce Picea abies or European silver fir Abies alba. The paper describes a new breeding site of the three-toed woodpecker in the Sobibór Forest, eastern Poland outside the distribution range of these two tree species and its relationship with Eurasian beaver Castor fiber. The birds occurred in dead alder forests and were recorded 3–4 years after forest started to decline due to the high level of surface waters associated with the keystone role of the beaver. The decaying cycle of trees was possible because the area settled by woodpeckers was protected as a nature reserve.