Search Results (6)

The Scaly-sided Merganser (Mergus squamatus) is an endangered duck endemic to East Asia. It usually gathers in single-species flocks through winter. Existing field records focus almost entirely on southern winter flocks. No prior work has described lone individuals spending winter in northern China. We conducted standardized three-year winter surveys (2019–2022) across five isolated ice-free river patches along the Taizi River, Liaoning Province, northern China, to document habitat use and flocking behavior of one solitary male. Despite the availability of five discrete overwintering sites, the focal bird only occupied two patches characterized by dense riparian concealment and low human disturbance, avoiding open, highly disturbed sites. Resource Selection Function (RSF) modeling indicated habitat attributes (concealment and human disturbance) strongly predicted site use (AICc weight = 0.79), whereas the abundance of heterospecific flocking partners (Common Mergansers Mergus merganser) exerted negligible influence (AICc weight < 0.01). This solitary male associated only with Common Mergansers, the species with the closest phylogenetic relatedness (mitochondrial genetic distance = 0.04365), and never aggregated with other sympatric waterbirds. Model comparison confirmed phylogenetic relatedness outperformed dietary similarity as a predictor of heterospecific flocking (AICc weight = 0.76). Our three-year observations of this single individual demonstrate that, when conspecifics are absent and suitable winter habitat is limited, this male prioritized high-quality, low-disturbance ice-free patches over social aggregation opportunities, and selectively formed mixed flocks with its closest phylogenetic congener. This multi-year case study provides rare empirical baseline data for understanding winter behavioral trade-offs of endangered cavity-nesting waterfowl under severe frozen river conditions, though all conclusions herein apply only to this focal male and cannot be generalized to the entire species. Full article

The coastal wetlands of Yancheng, Jiangsu Province, serve as a crucial overwintering and stopover site for rare waterbirds such as red-crowned cranes. The changes in their landscape pattern are directly related to the protection of regional wetland ecological functions and biodiversity. Using land use data from 2010 to 2022 to extract landscape pattern indicators for each period, this study adopts the Covariance–Analytic Hierarchy Process (Cov-AHP) to construct a comprehensive Landscape Fragmentation Index (LFI) for coastal wetlands, considering aspects including patch density, boundary complexity, spatial connectivity, and landscape diversity. Combined with multi-source indicators of Ecology–Economy–Society (EES), the Generalized Additive Model (GAM) and Geographically Weighted Regression (GWR) are adopted to systematically analyze the nonlinear response relationships and spatially heterogeneous driving mechanisms of landscape fragmentation. GWR is employed to reveal the spatial heterogeneity of the influence of each driving factor on fragmentation by mapping local regression coefficients. The results show that: (1) During the study period, the overall landscape fragmentation of the coastal wetlands in Yancheng, Jiangsu Province, exhibited a slow increase trend, with a spatial gradient pattern of “higher in the north and lower in the south, and higher in coastal areas than in inland areas,” reflecting the combined effects of varying levels of economic development and human activity intensity across different administrative regions and along the coast-inland gradient. (2) Based on the deviance explained by the GAMs, social factors generally had higher explanatory power for LFI than ecological and economic factors. Specifically, human population density and the proportion of construction land showed a significant positive correlation with LFI, while NDVI and the proportion of farmland exhibited obvious nonlinear effects under different fragmentation levels. (3) The GWR results indicated that the regression coefficients of the main driving factors were highly spatially non-stationary, and regions with high coastal development intensity had the most significant promoting effect on landscape fragmentation. The local coefficient maps further reveal that GDP and NDVI exhibit the strongest spatial heterogeneity, with their effects shifting from positive to negative across different sub-regions. The study demonstrates that the integrated framework of Cov-AHP combined with GAM and GWR can effectively characterize the spatiotemporal dynamics and multi-dimensional driving mechanisms of coastal wetland landscape fragmentation, providing a reference for the protection of coastal wetlands in Yancheng, Jiangsu Province, and the conservation of waterbird habitats represented by red-crowned cranes. Full article

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. Full article

In recent years, the altered hydrological regimes and frequent extreme hydrological events in its watershed have significantly affected the stability and biodiversity of the dish-shaped lakes (DSLs) ecosystem in Poyang Lake. This study uses long-term water level records from the Xingzi hydrological station, multi-source remote sensing imagery, and field surveys to assess how altered hydrological regimes and frequent extreme hydrological events influence the coupled hydro-ecological evolution of DSLs under different gate-controlled conditions. The results reveal the following: (1) After 2003, average monthly water levels declined by 0.84 m, shifting prolonged inundation depths from the 10.0 to 14.0 m range into the 5.5 to 9.5 m range. Extreme hydrological events disrupted the hydrological regimes, triggering a clear “collapse–recovery” succession in submerged plants and major shifts in shoal wetland vegetation. (2) Gate-controlled DSLs (GC DSLs) mitigated many of these impacts by reducing the autumnal drawdown in the water area change rate to 0.324 km²/d, curbing the upward expansion of emergent and hygrophytic vegetation during high-water-level years, and stabilizing habitats during low-water-level years, although different management strategies and substrate characteristics may still lead to divergent habitat trajectories. (3) The habitat heterogeneity exhibited by the DSLs’ vegetation communities along the elevation gradient had differential effects on migratory birds, and GC DSLs can offer migratory birds relatively stable resting habitats and food resources during extreme hydrological events. The study recommends that DSL management should adopt a hierarchical dynamic regulation strategy to balance natural hydrological fluctuations with human interventions, thereby strengthening the resilience of DSL wetland habitats to extreme hydrological events. Full article

Migratory waterbirds concentrated in freshwater ecosystems in mosaic environments rely on quality habitats for overwintering. At West Dongting Lake National Nature Reserve (WDLNNR), China, land-use change and hydrology alternation are compounding factors that have affected important wintering areas for migratory waterbirds. Presently, changes in the hydrology and landscape have reshaped natural wintering habitats and their availability, though the impact of hydrological management on habitat selection of wintering waterbirds is largely unknown. In this study, we classified differentially managed habitats and calculated their area using the normalized difference vegetation index (NDVI) to evaluate suitable habitat availability over the study period (2016–2017 and 2017–2018 wintering periods). We then used social behavioral association network (SBAN) model to compare habitat quality through species-species social interactions and species-habitat associations in lakes with different hydrological management. The results indicated that social interactions between and within species structured wintering waterbirds communities, which could be dominated by one or more species, while dominant species control the activities of other co-existing species. Analysis of variance (ANOVA) tests indicated significant differences in SBAN metrics between lakes (p = 0.0237) and habitat (p < 0.0001) levels. Specifically, lakes with managed hydrology were preferred by more species. The managed lakes had better habitat quality in terms of significantly higher habitat areas (p < 0.0001) and lower habitat transitions (p = 0.0113). Collectively, our findings suggest that proper hydrological management can provide continuous availability of quality habitats, especially mudflats and shallow waters, for a stable SBAN to ensure a wintering waterbirds community with more sympatric species in a dynamic environment. Full article

Human activity is the major factor driving the wetland degradation in shallow lakes. Human exploitation of lake wetlands alters the habitats of wintering waterbirds, and, in turn, waterbird diversity in the shallow lakes. In the present study, we surveyed species composition, abundance, and habitat characteristics of waterbirds in three types of wetland habitats (natural lakeside wetlands, paddy fields, and aquaculture ponds) at Caizi Lake, a shallow lake in the middle and lower Yangtze River during the wintering period, and investigated the effects of habitat change driven by human activity on the diversity of wintering waterbirds. There were significant differences in species composition and abundance among the three wetland habitats (natural lakeside wetlands, aquaculture ponds, and artificial paddy fields); however, there were no significant differences among the habitats with respect to the number of waterbirds. The numbers of overwintering waterbird species and waterbird individuals in aquaculture ponds and lakeside wetlands were significantly higher than the numbers in the paddy fields, indicating that wintering waterbirds prefer natural lake wetlands and aquaculture ponds. Principal component analysis of the three wetland habitat types revealed that factors influencing waterbird diversity include wetland area, vegetation cover, water level, and degree of human interference. Therefore, minimizing human interference and ensuring suitable habitats at specific periods could facilitate the maintenance of waterbird diversity. Full article