Birds and wind farms

Do wind turbines kill birds? Do they kill many birds? Is there anything that can be done to improve things? Read on for answers to all these questions.

Do wind turbines kill many birds?

Opponents of renewable energy often argue that wind turbines kill huge numbers of birds. The inference is that environmentalists who care about climate change should be more concerned about this.

There is no dispute that birds, and bats too, are killed by wind turbines. But estimates vary, and there is some suspicion that energy company studies may not be as rigorous as others:

  • An Australian ecologist estimated that each turbine only kills “one or two” birds each year, but there is a higher number of bats killed.
  • A Danish study (2016-2019) found only 1-2 bird deaths per year. This was only 0.1% of the local bird population.
  • A Canadian study (2011-2013) estimated 8.2 deaths per wind turbine per year.
  • Each turbine in a Norwegian wind farm was estimated to cause less than one bird death per year over a ten year period (2006-2016).
  • In the US, several older studies (2013-2014) suggest that each turbine may kill as many as 18 birds each year, and even more bats.

This is an enormous range of estimates. The variation may be partly explained by some using inadequate methods of counting (for example, searching for dead birds using dogs will yield a greater number than if the numbers are based on human observation). There have also been some improvements in wind farming (see below), meaning some older studies may show worse results.

It seems that both sides on this question have obtained figures favourable to their cause and not presented the full picture. I have tried to find unbiassed figures.

Nevertheless, we can conclude that killing of birds and bats is an issue that needs to be considered.

Comparisons are odious

It is instructive to consider other sources of birds deaths.

Estimates of deaths from different forms of power generation are also not very reliable, but it appear that nuclear and fossil fuel power plants cause far fewer direct deaths than do wind turbines, but when the impacts of climate change are considered, fossil fuel plants kill almost as many birds as do wind farms.

But to keep all this in perspective, compare the estimated annual rate of bird deaths from other causes:

CauseBird deaths relative to turbines
Wind turbines1
Domestic + feral cats2,000 to 8,000 times
Buildings550 to 1,000 times
Power lines20 to 1,300 times
Hunting210 times
Table: Bird deaths from various causes compared to deaths from wind turbines. The higher figures come from Canada while the lower figures comne from the US.

Even though these figures vary wildly and can be little more than guesses, they indicate that bird deaths from wind turbines are a relatively minor issue. For anyone concerned about bird safety, small improvements in other areas (e.g. destroying feral cats) would bring far greater benefits.

The effect on larger birds

Bird numbers are only one measure of the cost of wind turbines. Larger birds such as eagles, hawks and vultures are smaller in number and sometimes endangered, they would generally be considered as more worthy of preservation than smaller birds, and their populations are more easily compromised because they tend to lay fewer eggs.

It is estimated that larger birds are less affected by some of the other causes of bird death, and relatively more vulnerable to wind turbines than are smaller birds.

For example, there are concerns that the wedge-tailed eagle and the white-bellied sea-eagle are threatened by wind farms in northern Tasmania.

Therefore, the impact of wind turbines on these larger birds needs to be given special consideration. Nevertheless, wind turbines remain a relatively small danger to these birds too, except if wind farms are sited too close to critical feeding and breeding areas.

Reducing bird deaths

It is desirable to reduce bird deaths from wind turbines. Several measures have been proposed.

Location selection

If wind farms avoid location under migration paths and near feeding and nesting areas, impacts can be greatly reduced.

Making turbines more visible

Birds can fail to see a spinning wind turbine. However trials have shown that if one blade is painted black, it stands out and alerts birds to stay away. Reductions in bird mortality of more than 70% can result.

Sensing technology

Technology has been developed to sense the approach of large birds, and slow or even stop the rotation of the blades until the bird has passed. This technology has been trialed in Tasmania and the US and looks promising.

Deterring bats

To navigate in the dark, bats use a high frequency call which echoes off nearby objects. Transmitting ultrasonics at the same frequency can deter bats from that area, and in trials have more than halved bat deaths.

Conclusion

Bird deaths caused by wind turbines is an important issue that is receiving attention. Improved siting and design is reducing deaths, especially of larger birds.

The numbers quoted for bird deaths are inconsistent and sometimes appear to be biased towards the interests of the organisation undertaking the research.

Nevertheless, it is clear that wind turbines are a very minor cause of bird deaths, and some emotive statements by opponents of wind energy are grossly exaggerated.

Photo: Wind Farm Stock photo by Vecteezy