Collision risk of birds with modern large wind turbines

Abstract

We studied collision rate of birds with modern, large 1.65 MW wind turbines in three wind farms in The Netherlands during three months in autumn and winter. Collision rate, after correction for retrieval and disappearance rate, was 0.08 birds per turbine per day on average (range 0.05-0.19). Collision risk, i.e. the number of victims relative to the flight intensity of birds at the wind farms, was 0.14% on average. For nocturnal migrants, risk was as low as 0.01%, while the risk was 0.16% for local birds flying at night. In absolute numbers, the overall collision risk was similar to the 0.06-0.28% found for earlier-generation lower turbines that have a smaller rotor surface. However, given the comparatively large rotor surface and altitude range of the modern turbines, the risk was c. threefold lower than for smaller turbines. A large fraction of collision victims were diurnally active and local birds that were foraging in the area, rather than nocturnal migrants. Flight intensities of this group should be taken into account as well as that of nocturnal migrants, when calculating collision rate.