Wind energy harms birds less than expected

One of the Bird Observatory Sempach study conducted on behalf of the Swiss Federal Office of Energy concludes that about 20 birds die per wind turbine per year.

It is remarkable that in Peuchapatte, on the one hand, neither dead birds of endangered species nor dead birds of prey were found. This is despite the fact that it is often feared that wind turbines pose a particular danger to birds of prey.

Moreover, the number of birds that came to harm is much lower than it was feared when the turbines were built: The ornithological station Sempach assumed 0 to 1700 possible dead birds in its study, which was made before the construction of the wind farm. Skeptics and opponents of wind energy usually like to use the value of 1700 dead birds, which, as it now turns out, is far from reality.

"These results take bird protection and wind energy further," Reto Rigassi, managing director of Suisse Eole, the association for the promotion of wind energy, is pleased to say. "It shows exemplarily and very clearly that the fears in bird protection often have little to do with reality and lead to wrong conclusions."

Birds detect obstacle
The figure of 1700 birds killed per year is a purely theoretical figure: it assumes that birds, especially when migrating, simply fly straight into the blades of the wind turbine. "The 20 strike victims recorded per turbine show that the vast majority of birds are very aware of wind turbines and fly around them," Reto Rigassi elaborates. The birds are therefore capable of learning and normally recognize the turbine as an obstacle, which is also shown by the studies of the Calandawind turbine in the Rhine Valley and studies from Germany.

Using money for bird protection as efficiently as possible
The large difference between the theoretical values of the very costly pre-construction study and the effective results of the study during operation shows that theoretical forecasts are often very inaccurate, if not impossible, despite considerable effort.

"The project developers are spending a lot of money that is of little use to birdlife. This could be used much more effectively if, instead of very comprehensive theoretical studies, the real effects in operation were investigated in a well-founded manner. Based on these results, targeted measures could then be taken, if necessary. This is what is known as adaptive management," explains wind expert Rigassi. In particularly sensitive areas, more detailed studies of bird life are still appropriate in advance of wind farm construction.

Wind energy also helps birds
Suisse Eole is aware that numerous bird species are already threatened and that additional negative impacts should therefore be avoided as far as possible. However, the greatest threat to birds is climate change: 75 % of all bird species are threatened by climate change. Wind energy provides valuable winter electricity that optimally complements solar and hydro power, so that fossil heating systems can be replaced by heat pumps and gasoline and diesel vehicles by electric vehicles.

13 million dead birds due to traffic, cats and glass panes 
Every year, an estimated 10 million birds die in Switzerland because they hit glass facades and window panes. Domestic cats kill about 2 million birds and road traffic kills about 1 million birds per year. The study of the ornithological station Sempach, made during the operation of the wind farm Peuchapatte, shows that 20 birds die annually per wind turbine, which is the same number that a domestic cat preys on average annually. Extrapolated to an expansion of wind energy in accordance with the goals of the federal government's Energy Strategy 2050, a maximum of 20,000 dead birds could be expected annually.

About the study
The study took place between the end of February and mid-November 2015 at the Le Peuchapatte site at 1,100 meters above sea level in the municipality of Muriaux (JU). Three wind turbines of the type Enercon E-82 with a total height (incl. rotor) of about 150 meters have been located there since 2010. On a total of 85 days, the surroundings of the turbines were systematically searched for flapping victims within a radius of 100 meters (or 50 meters on 15 days in the summer months).

For the evaluation, the search efficiency, the daily retention rate of bird victims, and the probability of a collided bird falling on the surveyed area were considered. Calculations to determine absolute collision rates were conservative. At the same time, the intensity of bird migration was quantitatively recorded continuously (24 hours per day) for 265 days (26.2.-17.11.2015) using a BirdScanMT1 radar.

A median value of 20.7 impact victims per WT per year was determined. Collision victims were mainly small birds migrating at night, including goldcrests and thrushes, but also swifts and mallards. Bone fractures were visible in the X-rays of a large proportion of the impact victims examined in more detail.

The collision events were mainly detected during the migration season in spring and autumn. However, they did not always occur only at high migratory intensity in the altitudinal range of the plants. This shows that the correlation between migration intensity and the number of victims within the migration period is more complex than previously assumed. A large additional role is probably played by the different visibility conditions due to weather conditions. Further investigations would have to start here.

Source: Suisse Eole and SFOE