Trait-based indicators of migratory waterbird communities suggest decoupled ecosystem service potential across Yellow Sea–Bohai Gulf wetlands

Wetland site prioritisation often relies on site area and species richness, yet these metrics do not capture the functional composition of migratory waterbird communities that may underpin ecosystem services. This study developed a trait-direct framework that maps migratory waterbird functional traits to cultural, regulating, and supporting ecosystem service potential, cross-walked to Common International Classification of Ecosystem Services (CICES) v5.1 classes, and applied it to fourteen World Heritage-relevant sanctuary units of the Migratory Bird Sanctuaries along the Coast of the Yellow Sea–Bohai Gulf of China. Analyses combined 2024 peak counts from the China Bird Report database with standardised avian trait data from the National Dataset of Chinese Birds and AVONET. After controlling for site area and total abundance, body mass, tarsus length, bill width, bill length, and foraging mode were associated with regulating and supporting service potential, with body size, bill morphology, and substrate contact traits carrying the strongest signals. Plumage colouration was the clearest trait-level predictor of cultural service potential, and site area showed no consistent positive association with the cultural index. These focal trait associations remained robust in spatial-error sensitivity analyses. Species richness, Shannon diversity, and functional dispersion did not consistently recover these service-specific signals; the clearest signals occurred in trait-specific community-weighted means. The framework offers a transparent complement to area- and richness-based assessment that can flag candidate sites for evaluation, rather than a stand-alone basis for inscription decisions. The approach is reproducible where standardised traits and counts are available and supports service-explicit prioritisation across wetland networks.