Authors: Lakatos, Tamás; Marcolin, Fabio;Gallé, Róbert;Batáry, Péter;

Habitat fragmentation is critical for global biodiversity. To understand its effects, we investigated how local and landscape-scale variables, such as habitat fragment size (small vs large) and landscape configuration (isolated vs well-connected), affect bird species richness, abundance and functional diversity. We surveyed 60 threatened grassland fragments classified into two endangered grassland types: forest-steppes and kurgans. Forest-steppes are natural mosaic habitats occurring in the contact zone between grassland and forest. Kurgans are ancient burial mounds built of earth, spread across Eurasian steppes. In our research area, forest steppes were embedded in forest plantations, while kurgans were surrounded by an agricultural matrix with gradients of size and connectivity. We found that bird communities in large, well-connected forest-steppes had higher diversity and abundance than small, isolated fragments. Isolation negatively affected ground-nesting species in small forest-steppe fragments. Trait similarity of birds on well-connected kurgans was higher than on isolated kurgans. Species with small home range and ground feeding habits were more abundant on well-connected kurgans. Specialist birds had a higher abundance on highly isolated kurgans. These findings suggest that large, well-connected grassland fragments can significantly contribute to the persistence of grassland specialist birds in modified landscapes, thereby maintaining the ecological functionality of these habitats.