Estimating the impact of wind turbines mortality on the Red Kite (Milvus milvus) population in Wallonia

The Red Kite (Milvus milvus) is a European species of bird of prey, which, after sharp decline, showed rapid growth in Europe and Wallonia over the past two decades. The Walloon population is very unevenly distributed, with high densities in East Ardenne, while the species is almost absent from the Western half. Wind turbines are a cause of mortality for birds including the Red Kite. However, the actual impact of this mortality on populations remains poorly understood. We have estimated present, past and future mortality of wind turbines on Red Kites in Wallonia. We estimated mortality by searching two wind parks for carcasses during one year. We then generalized these results to Wallonia based on number of wind turbines and Red Kite densities. For 2023, we estimate a mortality of ca. 20 birds in Wallonia, which represents 1.1% of an estimated population of ca. 1900 birds. We then estimated past mortality and modelled future impact of wind turbines based on several scenarios of wind energy development. We inferred Population Viability Analyses using EolPop. Due to the species’ current high growth rates, the Walloon population does not appear threatened in any of the wind energy development scenarios considered. However, wind turbines expansion will have an impact on the overall population size, as well as on the number of fatalities. We advocate for continued monitoring of the species to detect future trends in the population, as well as further data gathering to improve models. High uncertainties remain, including on how the species will adapt to new habitats, and how current favorable habitats will change in the future. The Red Kite also represents a special case because of its current high growth rate, and more sensitive species (bats, black stork, harriers…) should also be studied.