Landscape forest loss decreases bird diversity with strong negative impacts on forest species in a mountain region

Understanding how biological communities respond to human-caused landscape disturbances is urgently needed to identify optimal spatial scenarios for preserving biodiversity in anthropogenic landscapes. Forest loss is increasingly cited as a major disturbance in these landscapes, but its impact on biodiversity in mountain regions with high endemism is not well understood. Here we evaluated how bird species diversity responds to forest loss in ‘La Montaña’ mountain region of Guerrero State, Mexico. We separately assessed the complete bird assemblage, and the diversity and spatial distribution of three different ecological groups (forest-specialists, habitat-generalists, and disturbance-adapted species) in the whole landscape mosaic. We found that the diversity of the complete assemblage decreased linearly with forest loss. However, species responses to forest loss differed among ecological groups, with the diversity of forest-specialist and habitat-generalist species increasing in more forested landscapes, and the diversity of disturbance-adapted species following the opposite pattern. Similarly, the proportion of sites occupied by forest-specialist birds decreased with forest loss, but site occupancy by habitat-generalist and disturbance-adapted birds was independent from forest cover. Our findings highlight that the optimal landscape scenarios for preserving bird biodiversity in general and forest species in particular, are those that maintain as much forest cover as possible.