Wind Turbines and Birds

by Brian Dunning
January 7, 2020

It's well known that birds often crash into buildings, powerlines, cars, even rocks and trees, and are often injured or killed. But many people call out wind turbines as an especial threat, with their enormous blades slicing through the sky. At a time when half the country is calling out for renewable energy to reduce carbon emissions, and the other half searches for arguments against it, the belief that wind turbines pose an unacceptable risk to birds is gaining traction among the general public. Today we're going to look at the facts and see what role wind power should best play in the future of birds.

Typically, when we hear of the debate over wind farms and their impact on bird populations, we assume that the two sides are represented by greedy energy companies in favor of the wind farms and environmentalists representing the side of the birds. This is the first and biggest piece of misinformation. It seems counterintuitive at first, but the most significant advocate for wind farms is the group you might least expect: the National Audubon Society, the world's largest and oldest nonprofit environmental organization dedicated to the conservation of birds. Just to be clear on this point that may come as a surprise to many people, their official position paper on wind power opens with this no-nonsense sentence:

Audubon strongly supports properly sited wind power as a renewable energy source that helps reduce the threats posed to birds and people by climate change.

Audubon strongly supports wind power because it reduces threats to birds — it does not increase them. Now there are important qualifiers in there; namely that wind farms have to be properly sited and managed, and we'll talk about all that in a moment. Audubon's position is founded upon thorough science. The paper continues:

Top scientific experts from around the world, including Audubon's own scientists, agree that the effects of climate change are happening now and will get worse. Scientists have found that climate change has already affected half of the world's species' breeding, distribution, abundance, and survival rates... Audubon's research shows a particularly stark threat for North American birds: Our Birds and Climate Change Report confirmed that 314 species stand to lose more than 50 percent of their current ranges by 2080... Properly sited wind power is an important part of the strategy to combat climate change.

So if you are hearing that wind farms are bad for birds, you're not hearing it from the best-informed bird conservationists. You're more likely hearing it from poorly-informed but well-intentioned amateur wildlife lovers, or even more likely, from fossil fuel interests intent on hampering the renewable energy sector. Wrapping opposition to renewable energy inside a superficially persuasive trojan horse of "wind turbines kill birds" is a devious and effective greenwashing ploy.

Another such ploy is the promotion of conspiracy theories that the number of birds killed by wind turbines is massive, but covered up by the wind industry. You'll find all of these conspiracy theories and more on websites that also promote the long-debunked "Wind Turbine Syndrome" said to sicken people; truckers transporting turbine blades are routinely killed because they're so dangerous on the road; the manufacture of wind turbines produces more greenhouse gases than coal and oil power plants; the turbines habitually burst into flames; building wind farms requires the "wholesale destruction" of forest habitats; and any other nonsense the fossil fuel interests can dream up. The claim that they kill huge numbers of birds is one that resonates best with many proponents of renewable energy, so it's the one you'll hear repeated most often.

So the big question, obviously, is how many birds are getting killed. This raises other questions like what types of turbines are most dangerous, and at what locations do they pose the most risk. If you've heard this discussed before, you've undoubtedly heard the comparisons with other types of human activity that kill birds. It is clear that wind turbines are responsible for about the smallest number of bird deaths among all anthropogenic causes. This is true even though the estimates range widely — about a full order of magnitude — for nearly all the causes studied. The numbers I'll give are for the United States alone, as studies as almost always confined to a single nation, and the US is the one for which the most data is available. Two things are changing about wind turbines year after year: more of them are being built, and they're getting taller. Data show that taller turbines clearly kill more birds than shorter ones; and obviously, the more turbines there are, the more birds will be killed. A third thing is also changing: reporting. Wind farms are generally on private property and reporting used to be rare; now it's becoming commonplace, so we have better data. Data I studied back in 2001 showed an average of 2 birds killed annually per wind turbine; today, with much better data and taller towers, that number is up to just over 5 (this analysis using 2013 data counting 44,577 turbines, with a range of 3.15 to 7.35 birds killed per year per turbine, with a mean of 5.25).

So with about 50,000 wind turbines averaging 5 birds a year apiece, that's a quarter of a million birds every year. The US Department of Energy has targeted the number of turbines to increase by a factor of six by 2050, and so we're potentially looking at about 1.4 million birds killed per year. The biggest manmade killer of birds is the humble cat (both domestic and feral); about 100 million of whom in the United States kill an estimated 2.4 billion birds each year — that's 24 per cat, or nearly 2,000 times as many as even the DOE's ultimate 6X buildout of wind turbines. Even collisions with building windows, which are the second biggest anthropogenic source of bird deaths, kill about 1 billion a year, many hundreds of times that of even the 6X buildout. The simple fact is that under no outlook will wind turbines ever be a significant contributor to birds killed by anthropogenic impacts.

However, for all of these numbers, the vast majority of birds being killed are passerines — basically songbirds — which exist in numbers large enough that no single source threatens their population (besides global warming). Of greater concern are raptors, due to their smaller numbers, their longer lifespan, and their much lower reproductive rates. Any impact to raptor populations is a significant one from which it's much harder to recover. And due to the difference in flight behavior between passerines and raptors, raptors are the ones most at risk from wind turbines. Raptors — particularly California Condors, Bald Eagles, and Golden Eagles — are where the US Fish & Wildlife Service and other conservation organizations focus their efforts.

In the United States it's illegal for these birds to be killed, and wind farm operators can face steep fines when it happens. In 2013, Duke Energy Renewables was fined $1 million, and in 2014, PacifiCorp Energy was fined $2.5 million, for various violations of federal acts resulting from protected bird species killed on their wind farms. Recognizing that it's not possible to avoid all bird deaths, permits can be issued to wind farms allowing them to legally kill a strictly limited number of protected birds, thus motivating all parties to do everything technology allows to avoid any accidents. For example, the Alta wind farm in Tehachapi, California — located in one of the places where rare California Condors are most common — is allowed to kill one single condor over its 30-year lifespan. So they employ various technologies intended to protect the birds.

Most California Condors are tagged, and when one approaches Alta, its radio transmission is detected and a shutdown signal is automatically sent to any turbines in its path, minimizing the risk of harm. A commercially available system called IdentiFlight uses camera arrays to scan the skies looking for the flight patterns of Bald and Golden Eagles, and when one of those is detected, a similar shutdown signal can be sent. Other experimental systems are in various stages of development or testing. These include radar to detect flocks of migrating birds, lights to illuminate turbine blades at night to make them more visible, thermal cameras that look for birds then attempt to identify them using artificial intelligence, optical cameras that spot raptors then produce a blaring audio signal to frighten them away, and even painting the turbine blades purple to attract fewer insects and thus attract fewer songbirds. Many of these systems are of limited utility, but substantial investment continues flowing to improve them.

But mitigation of an existing problem can only do so much. The best solution is prevention, and the best form of prevention is proper siting of the wind farms. Proper siting means, in general terms, staying away from bird migration routes and places where threatened raptor populations live. But there's also a lot more to it. In 2010, the US Secretary of the Interior commissioned the Wind Turbine Guidelines Advisory Committee to make these recommendations. This committee consisted of 22 members representing major conservation groups (including the Audubon Society), government wildlife departments, government energy departments, energy industry groups, and academics. Its 162-page recommended guidelines cover just about anything and everything you can imagine. In short, proper siting of wind farms minimizes the need for the mitigation technologies. The importance of proper siting is such that in the Audubon Society's position paper giving their strong endorsement of wind power, it's always qualified as properly sited wind power.

We already see the impact of proper siting by comparing the bird strike numbers of well-sited existing wind farms to that of poorly-sited ones. Passerine deaths can be reasonably expected to be cut in half, and some well-sited farms have never recorded a single condor or eagle casualty.

Global warming represents by far the greatest threat to bird populations, and especially to those that are already at risk. But it's hardly the only anthropogenic threat to birds that can be reduced by increased deployment of wind power. Air pollution from oil and coal fired power plants kills hundreds of thousands of people each year worldwide from lung cancer. There are probably about 50 times as many birds as people, and birds — due to differences in their respiratory systems — are far more susceptible to pollutants including particulates, carbon monoxide, ozone, sulfur dioxide, and heavy metals. Figures on bird deaths from this are not known, but it's probably within an order of magnitude of 10 million annually. This is another reason the Audubon Society supports wind power: if we replaced all the coal and oil power plants in the world with wind farms, bird deaths from human power generation would be cut by more than 90%; probably a lot more than 90%.

Wind turbines and birds are a perfect example of how statistics can be misused. When we trumpet only the number of bird lives lost, and say nothing about the much greater number of bird lives saved, we are being deceptive and abusing the data.

By Brian Dunning
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