Wintering ecology of Ibisbill (Ibidorhyncha struthersii) in Rapti-Khulekhani III–Samari (RKS) river complex of Makwanpur, Central Nepal

The Ibisbill (Ibidorhyncha struthersii) is a rare, habitat-specialist wader dependent on undisturbedriverine ecosystems in Asia’s high-altitude and mid-hill regions. This study examined the winteringecology and habitat factors influencing Ibisbill abundance in the Rapti– Khulekhani III–Samari (RBS)River Complex in Makwanpur, central Nepal. Standardized 3 km transect surveys were conductedalong the Rapti, Khulekhani III, and Samari rivers from November 2024 to March 2025. A total of 24individuals were recorded, with the highest mean density observed in Khulekhani III (6 birds/km²),followed by Rapti (2 birds/km²) and Samari (1 bird/km²). One-way ANOVA revealed significantvariation in density across sites (F = 8.33, p = 0.005), and Tukey’s HSD post-hoc test confirmed asignificantly greater density in Khulekhani III compared to the other rivers. The species exhibited aclumped distribution pattern (S²/̄=̄ 7), indicating aggregation in localized, suitable habitats. Thesehabitats were characterized by native riverine grassland dominated by Saccharum spontaneum andImperata cylindrica. Linear regression analysis revealed that human disturbance, sand extraction, andhabitat fragmentation negatively influenced Ibisbill abundance, while native riverine grass cover andgreater distance from settlements had significant positive effects. Elevation was not a significantpredictor. These results highlight the ecological importance of the River Complex and underscore theneed for targeted conservation actions. Effective protection of Ibisbill wintering habitat shouldprioritize the regulation of sand extraction, reduction of anthropogenic disturbance, and promotion ofcommunity-based conservation. Sustained monitoring and habitat management are critical to ensurethe long-term survival of this habitat-specialist wader in Nepal’s mid-hill river systems.