The impact of ecological water level on wintering migratory birds in Poyang Lake – Focusing on phytophagous geese

• Poyang Lake’s lakeshore Wetland was classified into five study areas by water level guarantee rate. • The Carex distributed in the 25–50% study area serve as the main food source for wintering migratory birds. • Proposing ecological water levels by establishing a coupled relationship between water levels and ecosystem health. • The importance of ecological water level regulation in key months was September > February > November > June. Poyang Lake is the largest freshwater lake in China and a globally important wintering habitat for migratory birds. The ecosystem health of Poyang Lake and the surrounding lakeshore wetlands is crucial for the wintering of birds. To better protect the health of bird wintering habitats, this study proposes an ecological water level calculation method that comprehensively considers zoning and phasing by establishing a coupled relationship between water level and ecosystem health. The results show that the ecosystem characteristics of the Poyang Lake lakeshore wetland are closely related to the water level. Based on the water level guarantee rate, the lake area can be divided into five sub-areas: 0%, 0–25%, 25–50%, 50–75%, and 75–100%, each with significant differences in vegetation characteristics. The average water levels in February, June, September, and November significantly impact the ecosystem health of the Poyang Lake lakeshore wetland and can serve as regulatory nodes for ecological water levels. Based on the life habits of geese and ducks, which are the dominant migratory bird species in Poyang Lake, the importance of ecological water level regulation is in the order of September, February, November and June, and the ecological water level in each month is recommended to be controlled as follows: the February average water level within the range of 6–8 m, ensure a minimum June average water level of 15 m, maintain the September average water level between 11–12 m, and stabilize the November average water level at 10 m. This thesis proposes a new way of studying the ecological water level of lakes, which can improve the existing research methods of ecological water level and better protect the ecosystem health of lakes and wetlands and fulfill their key ecological services.