The impacts of water level fluctuations of East Dongting Lake on habitat suitability of migratory birds

Understanding responses of habitat suitability of migratory birds to the water level is significant for providing countermeasures of wetland protection. East Dongting Lake serves critical wintering habitat for migratory birds along the East Asian-Australasian Flyway. However, the response relationships between the water level and the weighted usable area (WUA) for migratory birds remain largely unknown. Therefore, we established a habitat suitability model of migratory birds based on the Digital Elevation Model (DEM) and Normalized Difference Vegetation Index (NDVI) and recognized the change of WUA by comparing the transition of land-cover of similar hydrologic years before and after the operation of Three Gorge Dam (TGD). The results demonstrated that (1) the ecological water level of migratory birds in East Dongting Lake is 20.47–21.55 m. (2) Compared with the pre-TGD period, the start date of the ecological water level advanced by 25 days, the duration of the ecological water level increased by 16 days, and the fluctuation range of water level was more concentrated near the ecological water level, indicating that the TGD provides benefits for the migratory birds. (3) The most prominent transition among changes of land-cover was that the Reed beach (RB) (155.07 km2) and Marsh land (ML) (150.66 km2) changed to Tender Marsh land (TML) during dry hydrologic years, and the RB (171.90 km2) and ML (174.30 km2) changed to TML during normal hydrologic years. The findings show that water level changes habitat suitability of migratory birds by changing vegetation distribution at different elevations.