Trait-Structured Functional Reorganization Beneath Concordant Taxonomic and Functional Diversity in China’s Wintering Waterbirds

Land-use change affects biodiversity by altering both species composition and ecological functions. Taxonomic and functional diversity provide complementary perspectives, but their relationship can vary depending on how species traits are reorganized within communities. Here, we investigated nationwide patterns of wintering waterbird diversity in China by integrating bird observations (2015–2024), land-use information, and multidimensional functional traits. We examined spatial patterns of taxonomic and functional diversity, their relationship across landscapes, and whether species-specific associations with land-use gradients were structured by functional traits. Taxonomic and functional diversity showed strong spatial concordance and broadly similar associations with major land-use gradients. However, observed functional diversity was generally lower than expected under randomized species–trait correspondence, indicating non-random trait organization relative to the specified null model. Trait associations differed among land-use gradients, but only the agricultural-landscape gradient showed FDR-supported improvement in prediction for held-out species. These results show that strong TD–FD concordance can coexist with non-random trait organization and does not make the two biodiversity dimensions interchangeable. Joint consideration of species richness and functional traits can therefore provide a more complete basis for conserving wintering waterbird diversity in human-modified landscapes.