How many birds are killed every year by wind turbines?
In Germany it is a perennial issue.
With the country set to abandon nuclear power by 2022, and wind turbines planned to take up much of the slack, environmentalists are finding themselves in a bind because of the conflict between two issues close to their hearts: global warming and preservation of the nation’s wildlife.
It has to be said that estimates of the number of bird deaths vary widely.
One study monitoring the migrating flock of an estimated 1.5 million eider manoeuvring past a small wind farm recorded only a single collision event.
The environmental audit unit of the state of Brandenburg has counted a mere 681 bird deaths nationwide since it started keeping records on behalf of the German environment ministry in 1989.
A disproportionate number of those, however, are large, slow breeding and relatively rare birds of prey.
Other authorities cite much higher numbers.
Hermann Hötker, from the Michael Otto conservation centre in Bergenhausen, argues that in some areas the figure could be between one and 10 birds a year per turbine, based on Dutch and Belgian studies carried out near breeding areas.
Since there are 22,000 turbines in Germany, the avian death toll could be tens of thousands of birds a year or even more.
Some fly into the rotors or the tower; other, smaller, birds are flung to the ground by the powerful vortex created by the turbines.
Death rates vary per wind farm and are related to many factors, such as migratory paths, topography, sight conditions, weather patterns and wind turbine lights, which may disorientate the birds.
Hötker lists the difficulties of getting an accurate count, which lead some authorities to understate deaths.
Some corpses get lost in the corn fields. Others are scavenged by predators.
Landowners do not have an incentive to report dead birds.
Offshore wind farms are also a worrying unknown for campaigners: it is hard to count bird corpses that fall into the sea.
To opponents of wind farms, this is just one more argument against them.
Already they are accused of disfiguring beauty spots.
The power they provide is intermittent, depending on the vagaries of wind.
The sound they make purportedly causes insomnia and stress problems for some people. Also, the turbines are quite expensive and only last a little more than two decades.
But Germany remains committed to wind, and its own investment in turbines, as well as wind’s intermittency, has had effects on the energy situation all over central Europe.
Germany dumps its surplus wind energy at prices which, for instance, Czech nuclear power cannot undercut.
In wind farms’ defence, you also have to look at the many thousands of birds killed by cats or road traffic or by flying into windows.
Still, the Michael Otto institute favours measures like growing crops right up to the turbine towers to hide the presence of predators’ food, e.g. mice.
The argument wind farm supporters use that they feel trumps everything is that global warming will lead to even worse consequences for species survival.
The occasional bird caught in a wind turbine is a price worth paying to save the planet, they say.