ABSTRACT1. Rising global temperatures and the increasing frequency of climate extremes pose significant challenges to waterbird conservation. These effects might be mitigated by managing habitat heterogeneity through diverse water levels in waterbird habitats. East Dongting Lake (EDL), a critical wintering site within the East Asian–Australasian Flyway, has experienced a significant drop in winter water levels due to extreme drought and operation of the Three Gorges Dam. This study aimed to determine optimal water levels for supporting waterbird populations under these changing conditions.2. We examined winter waterbird populations at EDL from 2004 to 2021. Species were categorised into five foraging guilds based on established criteria. Environmental variables comprised daily water levels from the Chenglingji hydrological station, meteorological data from ERA5‐Land, and the 6‐month Standardised Precipitation Evapotranspiration Index (SPEI) for drought severity assessment. We used a generalised additive model (GAM) with a negative binomial distribution to analyse the relationships between waterbird abundance and these factors, applying GAIC‐based stepwise selection and varying‐coefficient functions to account for guild‐specific responses.3. In controlled areas of EDL, higher maximum water levels (MaxWL) during the wet season were positively correlated with waterbird abundance, while controlled areas also maintained high waterbird numbers during extreme drought years, providing crucial habitat refuges. In uncontrolled areas, MaxWL and SPEI positively influenced waterbird abundance, while minimum water levels (MinWL) and biological accumulated temperature (BioT) were negatively associated.4. In lakes where water levels can be regulated, regulation can be used to maintain habitat heterogeneity and food availability for wintering waterbirds. By adjusting local water management strategies within lake ecosystems, wetland managers can use these findings to support waterbird conservation efforts.