Climate driven rapid northward expansion of a songbird from subtropical to warm temperate zones: Dispersal corridors and future suitable habitat

While it is well established that climate change is driving species toward higher latitudes, the spatiotemporal dynamics of dispersal—particularly from subtropical to warm-temperate zones—remain poorly understood. Here, we combined ecological niche differentiation, functional landscape connectivity, and species distribution models (SDMs) to investigate the northward expansion of the Collared Finchbill (Spizixos semitorques) from southern China (subtropical zone) to northern China (warm temperate zone) over the past decade (2015–2024). The species was first recorded in Beijing in 2015, providing a clear temporal marker for the onset of rapid colonization at the expansion front. Our analyses revealed that compared to native-range populations, those in the expansion region show a partial shift in their ecological niche, occupying new environmental and geographic spaces. Functional landscape connectivity analysis further identified two main dispersal routes from the native range toward the expansion front region: a dominant “mountain corridor” along the Qinling, Taihang, and Yanshan ranges, and a secondary “plain corridor” across the eastern plains, with Mount Tai serving as a key dispersal hub. Moreover, SDM-based projections for 2060 and 2100 suggest that this northward expansion might continue and reach Liaoning Province, which could become a potential suitable habitat. Overall, our findings highlight the critical interplay between climatic niche shifts and landscape connectivity in facilitating rapid range expansion, providing a mechanistic framework for understanding how subtropical species colonize warm-temperate zones.