Abstract
Old-growth forest specialists are among the species most affected by commercial forestry. However, it is often unclear whether such species can persist and what their habitat needs are in managed forests. We investigated habitat selection of one such old-growth forest specialist, the white-backed woodpecker Dendrocopos leu- cotos, a species highly dependent on dead wood and typically found in primeval forests. Our aim was to understand factors affecting occupancy probability in man- aged forests in Central Europe, based on detection/non-detection data in 62 squares of 1 km2 in 2015 and 2016. We used occupancy models to compare a priori expectations about the relationships between occupancy and habitat characteristics at two spatial scales while accounting for imperfect detection. Occupancy was best explained by a proxy for food availability at a large (1 km2) scale and increased with the abundance of emergence holes produced by saproxylic beetles on standing and lying dead wood. Furthermore, occupancy was positively related to the mean diameter at breast height of live trees and standing dead wood at a small scale (0.25 km2 with high amounts of dead wood). Detection probability was negatively related to time of day, date and number of accessible survey points, and positively related to the number of observers. Our results demonstrate that detailed knowledge about a species’ foraging ecology is important for its effective conservation as sur- rogate criteria such as dead wood availability might not reflect the key factors required. For white-backed woodpeckers, it is important that the available dead wood is sufficiently colonized by saproxylic beetles, and for the conservation of the species, the habitat requirements of saproxylic beetles thus have to be taken into account as well.
Ettwein, A