This study analyzed the wintering habitat and pre-migratory inland movement of 12 whooper swans (Cygnus cygnus) equipped with a GNSS-based positioning tracker in the Nakdong River Estuary from December 2024 to March 2025. Minimum Convex Polygon (MCP) and Kernel Density Estimation (KDE) analyses were performed using 21,721 valid coordinate data to examine monthly spatial use and changes in core habitat areas. The average home range sizes were 113.38±251.36 ㎢ (MCP), 39.55±71.30 ㎢ (KDE 95%), and 7.21±12.19 ㎢ (KDE 50%), which reduced to 25.99 ㎢ (MCP), 12.72 ㎢ (KDE 95%), and 2.81 ㎢ (KDE 50%) when considering only data within the estuary. Most individuals exhibited high site fidelity (i.e., concentrated wintering activity), repeatedly using limited areas such as Eulsukdo, Maekdo and Samnak Ecological Parks, and Baekhapdeung. In March, some individuals dispersed inland to Junam Reservoir (Changwon) and Haepyeong Stream (Gumi) for short stopovers to secure energy replenishment or conduct exploratory activities before migration. Spatial use gradually expanded from February to March, and the core habitat shift from Eulsukdo to Maekdo Ecological Park was observed. These findings demonstrate the dual role of the Nakdong River Estuary as a key wintering and staging site along the East Asian–Australasian Flyway (EAAF), and provide scientific evidence for developing effective conservation strategies, including habitat protection, food provisioning, and avian influenza risk management