The Influence of Forest Protection Level on Nest Site Selection by the Great Spotted Woodpecker: Evidence from the Augustów Forest, NE Poland

Cavities are an essential structural element in forest ecosystems. In European forests, most cavities are excavated by the most numerous woodpecker species, the great spotted woodpecker (GSW) (Dendrocopos major). The impact of management practices on the availability of nesting sites for birds remains an important researched topic. Do the nesting sites of the GSW differ between protected and commercially managed areas? We analysed 173 GSW nesting sites in a large forest in Poland, divided into a national park and commercial forests. The aspen (Populus tremula) was the most preferred among tree species in both forest areas. In protected forests, cavities were less frequently excavated in the Scots pine trees (Pinus sylvestris) (10%) than they were in managed forests (30%). The significantly higher frequency of cavities excavated in a given tree in commercial forests suggests limited availability of suitable nesting trees. The GSW strongly preferred trees with wood softened by fungal decay for cavity excavation. Over 80% of all cavity trees were infested with wood-decaying fungi, with no differences between protection regimes. In commercial forests with a high proportion of pine trees, cavities can be excavated only in softened wood in the older stands. Protective recommendations include retaining more trees in poor health condition in commercial forests and ensuring an admixture of softwood tree species such as the aspen, birch (Betula sp.), and black alder (Alnus glutinosa) in commercial stands.