Predicting current and future distribution of the common waxbill using a mechanistic modelling approach

Biological invasions and climate change are two of the most pressing drivers of biodiversity loss worldwide. Anticipating where invasive species are likely to establish, as well as the potential impact of climate change on their range expansion, is essential for early detection and targeted management. In this study, we use a mechanistic species distribution model (SDM) to evaluate the current and future areas at risk of invasion by the common waxbill (Estrilda astrild), a widespread avian invader. Our model accurately predicts the species current range in Iberia and identifies additional climatically suitable areas, particularly in southern and western Europe. Under warming scenarios of +2 {degrees}C and +4 {degrees}C, suitable areas expand northwards, with over two-thirds of Europe classified as suitable under the most extreme scenario. These results suggest that the species is already operating near the cold limits of its thermal niche in parts of its invasive range, and that rising temperatures may remove these constraints, allowing expansion into previously unsuitable areas. Our findings demonstrate the power of mechanistic models in identifying regions at risk of colonisation and underscore the importance of early intervention and targeted monitoring in areas projected to become suitable.