Coexistence of overwintering avian species in Tibet: scale-dependent niche requirements for landscape structure with body size effects

Rapid environmental changes on the Tibetan Plateau pose significant challenges to overwintering avian assemblages in the resource-limited environments. However, traditional conservation strategies often focus solely on establishing reserve boundaries, failing to recognize that effective protection depends on maintaining complex internal landscape structures tailored to species-specific scale requirements. This study investigated how landscape composition and configuration affect the habitat selection and coexistence of overwintering avian assemblages in a reserve, with a specific focus on the modulating role of body size. Three sympatric species with distinct body sizes, including Black-necked Crane ( Grus nigricollis ), Bar-headed Goose ( Anser indicus ), and Ruddy Shelduck ( Tadorna ferruginea ), were investigated in the Black-necked Crane National Nature Reserve along the Yarlung Zangbo River valley in China’s Tibet. Using a multi-scale analysis ranging from 500 m to 6000 m and a pairwise coexistence index, this study quantified the relationships between species abundance, coexistence patterns, and landscape metrics derived from remote sensing data. The results demonstrated that landscape effects were strongly scale-dependent and modulated by body size. The larger-bodied G. nigricollis exhibited heightened sensitivity to landscape metrics at broader spatial scales, showing a distinct preference for contiguous agricultural lands as critical food subsidies. Conversely, smaller species responded significantly to fine-scale landscape configurations. Furthermore, the scale-dependent niche requirements for landscape structures were found to facilitate niche segregation and mitigate interspecific competition. Our findings underscore that merely delineating reserve boundaries is insufficient. Instead, conservation planning must adopt a multi-scale framework grounded in trait-based ecology. Priority should be given to safeguarding internal habitat heterogeneity, while concurrently fostering synergistic land-use practices across the reserve landscape. Specifically, maintaining the availability of post-harvest croplands and ensuring wetland connectivity are critical to bridging the gap between the fine-scale needs of smaller species and the broad-scale foraging ranges of larger species.