Risk for birds to be killed in wind farms
Whether a specific bird species is endangered from a specific wind turbine can be determined probabilistically. On the basis of space utilisation mappings of (planned) wind farms and specialised literature on the behaviour of specific bird species, the Veenker engineers at first analyse the probability of birds to stay in the critical area of the wind turbine. In addition, the seasonal presence, the proportion of flight time, the stopover distribution in the area considered and the distribution of altitude are taken into account. Subsequently, the collision probability during a flight through the area considered is calculated taking into account the possible natural avoidance behaviour of the bird. The summary of these complex values results in the individual collision probability of the bird. Conservatively it is assumed that this probability equates to the probability for the bird to be killed. The assessment of whether this means a significant increase in the risk to be killed and whether this infringes the German Federal Act for the Protection of Nature is carried out in accordance with the DIN EN 50126 and the rulings of the German Federal Administrative Court.
The following example is to illustrate the subject. There is the eyrie of a red kite within a planned wind farm. After verifying the basics, the calculations result in the risk for the red kite to be killed – due to a wind turbine – of 6.50 ∙ 10-5 killings per bird per year. Statistically this is equivalent to one killing in about 15,385 years. The following assessments, which are made in accordance with the DIN EN 50126 and the rulings of the German Federal Administrative Court, come to the conclusion that this is not a significant increase in the risk to be killed. So, in this case red kites and wind turbines do not exclude each other and the wind farm planner has a green light – at least concerning the risk of red kites to be killed in his wind farm.