The Influence of Low-Head Dams on the Biodiversity of Wintering Waterbirds in China’s Xin’an River Basin

The rivers in the middle and lower reaches of the Yangtze River are important wintering and migration stopovers for waterbirds. The hydrological characteristics of rivers directly affect the habitats of overwintering waterbirds and thus lead to changes in the diversity of overwintering waterbirds. The construction of artificial low-head dams has altered the natural hydrological processes of rivers, and therefore, investigating their influence on the composition of wintering waterbird communities is of great significance for the conservation and management of waterbirds. This study was carried out in the Xin’anjiang River Basin from October 2021 to March 2022, with 11 low-head dams selected as the research sites. Utilizing the sampling method, it investigated the species and abundance of wintering waterbirds in both the catchment and tailwater zones of these dams. Subsequently, the diversity of overwintering waterbirds in the two aforementioned zones was calculated, and their inter-zonal differences were analyzed and compared. The results of the study indicate that there are significant differences between the catchment area and the tailwater area of the “ZSJC” Dam (Z = 1.945, p = 0.001), whereas no significant disparities are observed in the species count and abundance of wintering waterbirds using that particular area between the catchment and tailwater areas of other dams. Compared with the catchment areas, the tailwater areas of the dams exhibit a more concentrated and abundant distribution of overwintering waterbirds, while the distribution of overwintering waterbirds in the catchment areas is more uniform than that in the tailwater areas. The 11 dams under study all demonstrated spatial turnover advantages, suggesting that catchment areas and tailwater areas make comparable contributions to β diversity. Bivariate correlation analysis in SPSS detected a significant correlation between dam vertical length and β diversity. In summary, low-head dam construction significantly affects the alpha diversity, beta diversity, abundance, and community composition of wintering waterbirds by modifying hydrological conditions and habitat structure in the Xin’an River Basin. This study provides a scientific basis for waterbird protection and low-head dam management.