Native forest cover, fragmentation, and seasonality shape functional diversity in forest bird communities

Abstract

Biodiversity encompasses genetic, species, and ecosystem diversity, all of which are threatened by habitat loss and fragmentation driven by human activities. We evaluated how the replacement of native Maulino forest by pine (Pinus radiata) plantations affects forest bird communities, focusing on functional diversity and landscape configuration. The study was conducted in South Central Chile across 22 landscape units (4 km² each), where bird surveys were conducted during both the breeding and non-breeding seasons. Functional diversity was assessed using functional richness (FRic), functional evenness (FEve), and functional dispersion (FDis). We recorded 26 forest bird species. Species richness was higher in native forests, where large tree users (LTU) dominated, whereas pine plantations favored shrub and vertical profile generalists. During the breeding season, FRic increased with native cover but declined with higher patch density, indicating that fragmentation constrains the functional breadth of communities. FEve and FDis showed weaker associations with landscape metrics, although fragmented forests tended to support more even but less functionally diverse assemblages. Seasonal patterns were evident, with of landscape structure being stronger in the breeding season. These results highlight the combined roles of habitat amount, configuration, and seasonal dynamics in shaping functional diversity. Conservation strategies should prioritize the retention of large tracts of native forest, limit further fragmentation, and maintain structural features such as mature trees to sustain key ecological functions.