Effect of Local and Landscape Variables on Bird Communities in Forest-Agricultural Mosaics in Northeast Luzon, Philippines

Agriculture is one of the major drivers of forest loss and fragmentation in tropical regions. Although typically associated with biodiversity loss, agricultural-forest mosaics are increasingly recognized as important targets for conservation as they can support significant bird diversity. This requires understanding how birds respond to habitat amount, quality, and configuration and using this to inform management strategies. Here, we investigated the effects of local and landscape variables at different spatial scales on bird species richness and abundance by conducting 131 point count surveys across forest and matrix habitats in six sites in Northeastern Luzon, Philippines. We found varying significance and direction of community responses to local and landscape factors across different functional groups based on diet and habitat dependency, showing that management interventions must be implemented with clear targets. Overall bird abundance increased with canopy openness, while richness did not show a significant response. In comparison, functional groups exhibited stronger responses. Forest dependent species responded positively to forest area, edge density, and tree species richness. However, several forest species known to inhabit the region were notably absent from our study, suggesting that historical anthropogenic disturbances may have led to their extirpation in the fragmented landscapes. Responses also varied in strength with the spatial scale at which the landscape metric was considered. Therefore, habitat management needs to be tailored to the species targets and spatial scales relevant for conservation.