Habitat Fragmentation in Urbanized Landscapes Favors Bird Species With Darker Plumage.

Plumage coloration is an important trait influencing signaling, communication, and ecological adaptation in birds. While some studies have documented that urbanization favors bird species with darker plumage, the specific filtering effects of habitat fragmentation, a common structural consequence of urbanization, remain largely unexplored. We examined how habitat fragmentation favored bird species with particular achromatic plumage color, based on 82 breeding bird species recorded across 30 remnant woodlot patches within a rapidly urbanizing landscape in southwest China between 2017 and 2024. We calculated assemblage-level achromatic plumage color from species occurrences and species-level whole-body mean color values. As hypothesized, assemblages in smaller patches and patches with higher edge proportions had darker plumage when accounting for species richness. This pattern was slightly more pronounced in males than in females. Contrary to our expectations, assemblages in patches with lower cover percentage of woodlands and higher percentage of built-up areas surrounding patches were not lighter. These results suggest that darker species, especially those with darker males, are more likely to persist in highly fragmented habitats. By interpreting plumage coloration in relation to potential advantages of camouflage, boldness, and pollution resistance, this study provides insights into trait-based species sorting in urbanized landscapes.