Predicting the suitable wintering distribution areas for the Mergus Squamatus in Sichuan Province based on the MaxEnt model

The Mergus squamatus is an East-Asian endemic and National First-Class Protected Species in China. Quantifying its current habitat distribution in Sichuan Province provides the baseline data required for evidence-based conservation planning. We collated 327 occurrence records from field surveys and the BirdReport, retained 91 high-quality presences after spatial filtering, and coupled them with 25 ecologically relevant predictors. A tuned MaxEnt algorithm was used to (i) project the wintering suitable habitat across the province and (ii) identify the principal environmental drivers of habitat selection. Model predictions revealed that the most suitable wintering areas are concentrated in the Sichuan Basin and the southwestern Sichuan mountainous areas. Within this region, mergansers almost exclusively occupy riverine wetlands associated with third-order or higher tributaries of the Yangtze drainage, specifically the main-stem Yangtze, Tuo, Min, Fu, Jialing, Qu, Qingyi, Anning and Dadu watersheds. Land-cover type (Lc, 28.6%), elevation (27.2%), Human Influence Index (HII, 22.4%) and precipitation of the warmest quarter (bio18, 7.5%) were the four most influential variables, together explaining 85.7% of the observed habitat suitability pattern. We therefore recommend: (1) Designating additional protected sites to increase coverage of the species’core wintering habitat; (2) Expanding the spatial extent and upgrading the protection status of existing reserves that overlap high-suitability areas; (3) Establishing a long-term monitoring scheme, implementing science-based patrols, and launching community outreach programmes to raise local awareness and reduce anthropogenic disturbance.