Forest management in mountain mixed forests has moderate impact on breeding bird assemblages, but it substantially decreases the diversity of rare taxa

Assessing the impact of forestry on biodiversity has become a common tool for evaluating the sustainability of forestry. Birds are often used as indicators of biodiversity and sustainable management. We compared bird diversity and abundance between protected (natural) and managed forests representing temperate mixed forests of Central Europe dominated by beech, spruce, and fir. The bird census was performed in 2021 and 2022 using the point-count method at 173 census points (88 in strictly protected areas; 85 in managed forests) along with habitat surveys focused on potentially most important habitat variables that influence habitat selection of birds. Natural forests hosted higher bird species richness, diversity, and abundance than managed forests nearby. A positive influence of the forest conservation regime was that it exhibited a higher abundance of cavity nesters and threatened birds of the European Union that are listed in the Birds Directive (NATURA 2000 species). The mean volume of the total standing dead wood (SDW) was more than seven-fold higher in natural forests (32.59 m³·ha⁻¹) compared to managed ones (4.40 m³·ha⁻¹). Increased volume of the coarse SDW (diameter >50 cm) had a positive effect on the diversity and abundance of birds. Increasing percentage of clearings had a significantly positive effect on overall bird diversity and abundance, with the exception of NATURA 2000 species. While the proportion of beech did not have a significant effect on overall species richness, diversity, or abundance, NATURA 2000 species and cavity nesters were positively influenced by its rising proportion in the stands dominated by conifers. The goal of modern forestry should include the cultivation of heterogeneous, structurally diverse forest stands, with high compositional diversity, and a considerable amount of dead wood. The impact of forestry should not be measured only on the basis of overall diversity and abundance, but also with the use of rare, sensitive, specialized forest-interior species reflective of high ecological and conservation value.