Urban Parks and Wetlands Support Complementary Bird Assemblages in Huai’an, Eastern China

Urban biodiversity planning depends on whether terrestrial and aquatic habitats retain the same species or make non-redundant contributions to the observed species pool. We surveyed 14 urban parks and four transects nested within two wetlands in Huai’an, eastern China, during two rounds. The audited counts comprised 2085 individual records and 58 species. Observed richness was higher on the sampled wetland transects (median 21.5 versus 16.0 species), but limited independent wetland replication precluded a general habitat-effect claim. Parks and wetlands each contained 43 species, with 28 shared and 15 recorded exclusively in each habitat class. Across 14 park–wetland pairs of pooled landscape units, mean Sørensen dissimilarity was 0.457, partitioned into turnover of 0.353 and nestedness-resultant dissimilarity of 0.104; turnover accounted for 77.3% of the summed dissimilarity. A classification of all 58 species using AVONET showed that 11 of the 15 wetland-only records had a wetland habitat affiliation, whereas eight park-only records were associated with forest or woodland and four with shrubland. These are global species-level traits, not evidence of local habitat specialization. Environmental correlations remained exploratory and did not survive within-family false-discovery-rate adjustment in the primary rank-based analyses. The results support observed compositional complementarity within the sampled landscape, while imperfect detection, two survey rounds, unmatched habitat area and only two wetland systems limit generalization. Conservation should retain both terrestrial green spaces and heterogeneous wetland habitats, with attention to habitat quality and hydrological structure.