Die Rolle von Eiche, Totholz und Efeubeeren bei der Habitatwahl des Mittelspechts

Abstract

Due to their habitat needs, woodpeckers are generally considered to be excellent indicators of forest habitat quality and biodiversity. In the EU and in Switzerland, the middle spotted woodpecker acts as a flagship species for nature conservation in forests. After several decades of decline in the Canton of Zurich, the population of the indicator species more than doubled between 2002 and 2012. The reasons for this positive development are so far unknown. It is hypothesized that an increased availability of ivy berries, sometimes eaten by the middle spotted woodpecker, may have contributed to the population growth. Based on the woodpecker monitoring 2012 in the Canton of Zurich, in 2013 the availability of trees with ivy berries at sites with and without presence of the middle spotted woodpecker was examined in eight forests. At the same time we also studied the availability of oaks and standing dead trees, two habitat factors well known to be important for the middle spotted woodpecker. Results revealed significantly shorter distances to large oaks and a tendency towards shorter distances to dead trees at points with middle spotted woodpecker presence than at points without. The distance to trees with ivy berries, on the other hand, was the same at presence and absence points. Occurrence probability of the middle spotted woodpecker was best explained by the distances to the closest large oak and to the closest standing dead tree, respectively. The importance of ivy contributing to the structural diversity in forest ecosystems and providing food and refuge to many species is widely recognized. Therefore, ivy should not be eliminated and oaks and dead trees should be continued to be fostered.