Ecological impacts of recreational transformation and war on bird communities in the Siverskyi Donets river floodplain: diversity, synanthropization, and restoration strategies

• People activity leads to a complex transformation of the entire forest ecosystem. These disturbances taken together affect the habitat conditions of birds. • The disturbance factor should be taken into account in relation to birds during military conflicts. • Data can be used to identify changes in bird communities influenced by military conflicts and on the gradient of recreational transformation of riverbank tree biotopes. This study examines the diversity, structure, and ecological changes in bird communities along the Siverskyi Donets river and its surrounding recreational areas, focusing on the impacts of recreational transformation. It aims to assess how these changes affect bird community composition, α- and β-diversity, synanthropization levels, and ecological balance. Additionally, the study compares the effects of recreational and post-war habitat destruction on bird communities and suggests strategies for habitat restoration after the war. We used Principal Component Analysis (PCA) to explore the relationship between bird community diversity and the level of recreational transformation along a biotope gradient: floodplain oak forest – tourist bases – park. The negative impact of recreational pressure increases along this gradient, with average bird density rising from 2.83±0.48 pairs/km² in the oak forest to 3.82±0.90 pairs/km² in the park. At the same time, species richness drops from 33 to 22, synanthropization values increase from 0.67 to 0.86, and α-diversity and community balance decrease. We predict that if habitats are not completely destroyed by war, bird communities will respond similarly to the combined pressures of habitat destruction and disturbance from military activities, as they do to recreational pressure. Following the war on Ukraine, we recommend establishing a continuous network of forest remnants, planting multi-species, multi-layered vegetation, creating artificial nests and shelters for birds, and preserving ruderal patches as breeding and feeding grounds. Collaboration among biological, social scientists, and conservation organizations is essential to restore Ukraine's ecosystems and biodiversity.