Totholz – existenziell für den Weissrückenspecht in Nordbünden | Dead wood – a vital necessity for the white-backed woodpecker in the Grisons

Abstract

The white-backed woodpecker (Dendrocopos leucotos) is a species considered to be associated with the primeval forest and is regularly to be found in the steep, little managed, beech-filled forests of the northern Grisons. This gave an opportunity to study its dependence on the presence of dead wood, to determine the supply available in its typical habitat and to document the evolution of the formation of dead wood. Direct observation showed that the woodpecker found up to 97% (n = 394) of its food in dead parts of trees. Two forest areas which should provide the ideal habitat for the white-backed woodpecker in the northern Grisons have a living standing stock of over 400 m3 per hectare but also dead wood amounting to 100 m3 of standing crop per hectare. Based on comparative photographs it is estimated that, in the forests used by the white-backed woodpecker, the death rate in the tree stands is between half and three-quarters of increment. Since the dieback process follows successive phases, this gives a supply of dead wood in varying stages of decomposition. This specific biotope is important not only for the white-backed woodpecker but also for a large number of other species which depend upon dead wood, particularly many insects and fungi. In order to preserve this distinctive ecosystem, the forestry service of the Grisons is endeavouring to create a network of natural forest reserves, in which are represented the numerous forest ecological communities typical of the canton. The possibilities for an exploitation of the timber whilst maintaining a sufficient quantity of dead wood should yet be investigated.