Evergreen ivy vines as a key element maintaining the high diversity of birds wintering in Central European forests

Animals face numerous difficulties during winter due to food deficiencies and adverse weather conditions. They are likely especially important in landscapes affected by humans like managed forests, which often have simplified structures that result in a deficiency of arboreal microhabitats crucial for many species. We examined the effects of ivy vines’ presence in Central European upland deciduous forests on bird diversity during winter. We found that forest patches with dense ivy vines on trees strongly attracted wintering birds, which increased the species richness, abundance, and phylogenetic diversity of bird communities. This was true for all plots, regardless if they were located in forest interiors or on the edges. Ivy was the crucial element for bird diversity in forest interiors, whereas in forest edges, veteran trees, dead trees, and bushes also played a substantial role in bird wintering activity. This study demonstrated that lianas (i.e., ivy vines), generally rare elements of temperate forests, are important for the maintenance of forest biodiversity, particularly during the winter periods. Therefore, forest patches with ivy vines should be protected in European forests to enhance overall forest biodiversity.