Contrasting roles of standing and downed deadwood in nest-site associations of sympatric woodpeckers

Woodpeckers are primary cavity excavators, but quantitative evidence on multi-scale nest-site associations of sympatric woodpecker assemblages remains limited in Northeast Asian temperate forests. We examined nest-site associations of six sympatric woodpecker species in an old-growth mixed coniferous–broadleaf forest dominated by Korean pine in Liangshui National Nature Reserve, Northeast China. We assigned 120 confirmed nests to six species and compared nest plots with 120 paired reference plots using conditional logistic regression. Leave-one-species-out models were used to assess whether the pooled stand-scale associations were driven by any single species. We then compared used nest trees with a recorded pool of candidate trees, while cavity characteristics and interspecific differences were examined as secondary analyses. At the stand scale, nest occurrence was positively associated with downed wood density and live-tree density, negatively associated with snag density, and was higher closer to water and farther from human disturbance. The positive association with downed wood density and the negative association with snag density were retained after each species was excluded in turn. Relative to the 720 locally recorded candidate trees, used nest trees were more often decaying, were disproportionately represented by Abies nephrolepis and Picea spp., and had larger DBH, greater height and higher bark bareness. Secondary analyses indicated non-uniform cavity entrance orientations and interspecific differences in nest-tree and cavity characteristics. These results indicate that nest-site associations of sympatric woodpeckers are scale dependent and that standing deadwood, downed wood and decaying nest trees represent distinct habitat components. Habitat assessments in similar forests should therefore record live-tree structure, downed wood, standing deadwood and focal-tree condition as separate components.