Bioaccumulation and Environmental Pathways of Heavy Metals in Wetland Birds: Evidence from Feathers and Ecosystem Compartments

Heavy metals pose a persistent ecological risk to wetland ecosystems and their avifauna, yet the pathways and sources of exposure remain insufficiently understood. This study combined two complementary approaches: (1) analysis of long-term (2000–2020) monitoring data from Poyang Lake to assess correlations between bird abundance and waterborne metal concentrations, and (2) targeted sampling in the Houtan Wetland Park to measure Cu, Pb, Zn, Ni, Cr, and Cd in bird feathers and in multiple environmental media (water, sediment, soil, and aquatic plants) across two periods and three sites. In Poyang Lake, correlations varied by species, with some resident waterbirds positively associated with moderate metal enrichment and sensitive migratory species showing negative relationships. In Houtan, Zn consistently exhibited the highest concentrations across all matrices, and feather metal profiles closely paralleled those of sediments and soils, indicating benthic foraging as a key exposure pathway. Metal-specific correlations revealed distinct environmental linkages, and inter-metal relationships in feathers suggested that Cu, Ni, and Cr share common anthropogenic sources, whereas Pb, Zn, and Cd likely derive from diffuse or independent inputs. These findings demonstrate the effectiveness of feathers as non-invasive bioindicators, clarify the element-specific pathways of metal accumulation, and provide a scientific basis for targeted pollution control strategies in urban wetland conservation.