Smart flying in challenging skies: How Red Kites adjust wind turbine micro- and meso-avoidance across weather and experience

Understanding bird avoidance behaviour at wind turbines is essential for accurate collision risk assessment. We provide one of the first empirical analyses of both micro-avoidance (avoidance of rotor-swept airspace) and meso-avoidance (avoidance of the entire turbine) in Red Kites (Milvus milvus), based on high-resolution GPS telemetry integrated with turbine operational data and simulation-based error correction. Red Kites showed consistently high avoidance rates: meso-avoidance averaged ~ 90% and micro-avoidance ~ 80%, resulting in an overall avoidance probability of ~ 98%. Avoidance varied with individual experience-birds with greater prior exposure to turbines showed lower meso-avoidance. Whether this reflects habituation and increased collision risk or improved spatial awareness remains to be investigated. Environmental conditions also modulated avoidance: higher wind speeds and increased cloud cover were associated with stronger avoidance responses. This suggests that under unfavourable weather, Red Kites adopt more cautious flight behaviour that may be associated with lower collision risk. In contrast, turbine-specific features (e.g. tower height or rotor diameter) had no significant effect. These findings indicate that Red Kites flexibly adjust their spatial behaviour in response to turbine exposure and environmental context. By refining species-specific avoidance estimates and identifying mechanisms influencing risk, our findings improve the empirical basis for collision risk assessment in Red Kites and highlight that avoidance behaviour may vary with environmental conditions and turbine experience.