Reconciling wind energy development with bird conservation: A comparative study of flight behaviour in raptors to understand and mitigate wind turbine collision risk ; Concilier l'énergie éolienne et la conservation des oiseaux : Une étude comparative du comportement de vol des rapaces pour comprendre et atténuer le risque de collision avec les éoliennes

Wind energy development is a major component of the strategies to decarbonise energy production and mitigate anthropogenic climate change. However, it leads to bird mortality due to collisions with wind turbines, especially in raptors. To assess the sensitivity of different species to wind turbine collisions and identify effective mitigation measures, detailed information on the species-specific flight behaviour is required. In this comparative study, bird-borne GPS tags were used to investigate collision-related aspects of flight behaviour in six raptor species: Montagu’s Harrier, Hen Harrier, Marsh Harrier, Common Buzzard, Short-toed Eagle and Red Kite, the latter being perceived as one the most collision-prone species in Europe at present. In total, 377 individuals were tracked in 15 study areas in six European countries. First, as the flight height of birds is a crucial determinant of collision risk, we assessed methods which could improve the accuracy of height data from GPS tags. The highest accuracy was obtained in high-frequency GPS data (GPS fix interval of 2-3 s).Subsequently, such high-frequency data were used to determine the frequency distributions of flight height in the breeding areas, and assess the effect of wind turbine dimensions on collision risk. In five out of six species, the flight height distributions had a pronounced mode below 25 m above ground. Consequently, the theoretical collision risk decreased substantially with increasing ground clearance of wind turbines. Moreover, with increasing rotor diameter (at fixed ground clearance), the collision risk per MW decreased. By contrast, in Short-toed Eagle, a more uniform flight height distribution and opposite effects of wind turbine dimensions on collision risk were found.Finally, the species-specific sensitivity to wind turbine collisions in the breeding areas was assessed based on the time spent in flight, the proportion of flights at collision risk height and the distance travelled from the nest location. Large interspecific differences ...