Breeding habitat of a mysterious forest bird – the woodcock in the Swiss Prealps

Abstract

The woodcock (Scolopax rusticola) is classified as vulnerable on the Red List of breeding bird species in Switzerland. In the past decades, the woodcock abandoned most breeding habitats in the lowlands and in the eastern part of Jura Mountains, and populations nowadays are restricted to areas in the Alps and the western parts of the Jura Mountains. The reasons for the decline are largely unknown. Moreover, there are no studies about breeding habitat use in eastern Switzerland. In this study we assessed the habitat use at a small scale in the forest reserve Amden (St. Gallen) in the eastern Prealps during the breeding season. To detect woodcock prescence we used a non-invasive method of sampling indirect traces. We compared 30 plots with woodcock presence with 30 randomly selected control plots with respect to site characteristics, forest stands, structure elements and soil characteristics. In a multivariate logistic regression we identified the most important factors discriminating woodcock plots from random plots. Important habitat features were horizontal dead wood, grass and fern canopy cover, earthworm weight and soil resistance. The number of horizontal dead wood and fern canopy cover was much higher in woodcock plots than in matched control plots. Woodcock preferred soils with high biomass of earthworms and a low penetration resistance. Thus, food resources and accessibility and predator avoidance were the most important factors of habitat selection by woodcock in this study. Based on these results, an effective conservation of woodcock should favour open forest structures, cover elements, a lush field layer and humid soils with a high density of earthworms.