Middle-spotted Woodpecker in beech-dominated mountain forests are reliant on dead wood: effects of habitat structural, compositional quality, and snags

The Middle-spotted Woodpecker is an indicator of structurally complex deciduous forests, typically associated with mature oak stands but occasionally found in beech dominated forests, including at elevations exceeding 1,000 m. Although standing dead wood is often used for nesting and foraging, its necessity for the species’ occurrence remains debated. This study examined the relationship between D. medius presence and standing dead wood characteristics in beech-dominated low-mountain forests of the Perșani Mountains, central Romania. Standardized national woodpecker monitoring protocols were applied at 25 fixed points. Standing dead wood variables (density, diameter at breast height (DBH), height, volume, and basal area) were measured across three habitat categories: all forest types, mature and old stands (> 70 years), and stands containing at least 10% oak. Snag density did not differ significantly between plots with and without Middle-spotted Woodpecker, yet occupied plots contained taller and thicker snags, with predicted occurrence probabilities highest at DBH > 60 cm and height > 25 m. No significant differences were found for basal area or volume. In predominantly beech stands, the species’ presence appeared to be influenced by the availability of standing dead wood and the presence of rough-barked species. These findings confirm the species’ strong association with mature deciduous forests, particularly where oak is present. The increasing probability of occurrence with higher oak proportions in standing dead wood underscores the ecological importance of conserving large, old trees and mixed forest structures for Middle-spotted Woodpecker persistence.