Over the hills and far away: linking landscape factors with cavity excavation on living forest trees by the Black Woodpecker (Dryocopus martius, L. 1758)

Abstract

The Black woodpecker (Dryocopus martius, L. 1758) is the largest primary cavity digger in western Europe. Its cavities represent an essential microhabitat for many other forest species but the landscape factors that influence the cavity digging by the Black woodpecker are poorly known and rarely been quantified at the scale of the vital range. We used cavity maps by foresters and naturalists to build a large (2689 cavity bearing trees) database distributed over 11 sites in France. Based on this and on a set of pseudo-absence data, we analysed the effects of stand composition and landscape features at three different scales around each plot corresponding to a forest management unit (10ha), the core (100ha) and extended (250ha) vital range scales. We showed that landscape shape index and forest composition (mixed forests) had significant effects but that the magnitude varied across the three scales. The Black woodpecker tend to avoid conifer-dominated stands to dig cavities, and also prefer homogeneous forest landscapes with low edge densities. These results vary with precipitation and slope with stronger effects of landscape in wetter climates and higher slopes. Although forest management rarely modifies the landscape in western Europe, a better understanding of the features that influence cavity digging by the Black woodpecker may help to better integrate their conservation at the management planning scale. Our results also show the importance to maintain mixed broadleaf-conifer forests as well as connected forest landscapes to favour features that benefit forest biodiversity at the large scale.