The Truth Of Bird And Bat Deaths By Wind Power. (And How To Prevent It?)

One of the biggest concerns that potential wind turbine owners have is the bird deaths by turbines. And it is indeed a valid concern because most people who opt for wind power for their homes have some inclination to do something good for the environment. But when we research this topic, there is so much misinformation out there. I have seen many organisations representing data in Such a way that it can easily misguide someone. Don’t worry; we are not here to sell you anything or give you any wrong idea. We are simply going to discuss facts gathered from highly reliable researchers and represent them so that you can decide whether you are with or against wind power.

So How many birds do wind turbines kill a year? Even though it is hard to estimate the exact number, but according to a 2013 study, around 234,000 birds die each year in the USA because of wind turbines collisions. 

However, if you look at the bird death caused by fossil fuels, A 2009 study published by the Journal of Integrative Environmental Sciences estimated it to be 24 million in the USA alone.

Knowing one number will not tell you about the complete picture. These are many aspects to this, and to have a better idea, we need to explore them.

Bird Deaths per gigawatt of electricity

A little thinking will help you realise that since the amount of power generated by fossil fuels is significantly higher than wind, their contribution would surely be higher. Though that still doesn’t help us determine how much damage does wind turbine cause compared to other sources

A great way to do that is to compare bird deaths for similar power outputs.

2009 study compared the avian fatalities per gigawatt for various power sources.

Source  Fatalities per GWh
Wind Power  0.27
Nuclear Power  0.6
Fossil Fuels 9.4


As you can see from the table, fossil fuels are 35 times more lethal for birds than wind power for the same amount of energy generated.

Birds Killed By Other Sources

Several other human-made sources contribute to bird fatalities in massive numbers. The exact number of deaths is hard to estimate, but the U.S. Fish and wildlife service compiled several pieces of research to provide a reasonable estimate. It is to be noted that all these sources are human-made and does not account for the deaths caused by natural causes.

Cause  Estimated Bird Fatalities in U.S
Cats  2,40,00,00,000
Collisions with building glass 59,90,00,000
Collisions with vehicles 21,45,00,000
Collisions with electrical lines 2,55,00,000
Oil pits 7,50,000

Source – U.S. Fish and wildlife service 

It is evident from this data that buildings and cats are far bigger culprits when it comes to bird deaths. These kill several thousand times more birds than wind turbines.

Why wind power poses a threat to birds

Birds from over 200 species are documented to be killed by wind turbines. Passerines are the most common victims, followed by raptors ( Falcons, eagles and Hawks). However, raptors are more vulnerable due to their long lives and lower reproductive rates.

In the united states, it is estimated that by 2030, wind power will contribute to 20% of all energy produced. With the increased number of wind turbines, the number of avian fatalities will soar as well. Statistical models predict that as many as 1.4 million birds could die each year by wind turbine collisions if corrective measures are not taken.

The location of the turbine also plays a significant role. Not all areas pose the same risk. California, for example, has an average bird death rate of 7.85 per turbine per year, while the number is 2.92 for the great plains.

At the landscape level, the location of the turbine can also influence the number of fatalities. The birds are more vulnerable at places with higher avian activity like migratory routes, river ridges, coastlines etc. How birds utilise the landscape is another factor that determines the number of casualties. The soaring birds are often unable to evade the blade in time and often swept in the rotating zone. In the daylight, some birds fly at lower altitudes and get entangled in the sweeping rotor zone. Birds also cruise at lower altitudes while looking for food and collide with the turbine.

Turbines can also cause habitat loss for many species. If improperly placed, it can destroy a specific habitat that is crucial for many species’ survival.

The design of the turbine is also a critical factor in bird fatalities. Currently, most turbines have a height of 475 to 639 feet (the elevation of the turbine from the ground, including the blade). As the hight of the turbine increases, the bird mortality rate increases as well. Studies suggest that any structure which is more than 350 feet from the ground level poses a risk for the birds.

Based on these observations, authorities have designed a regulatory framework to minimise the damage.

How to prevent wind turbines from killing birds

Researchers are not giving up on birds, and neither are they giving up on wind power. Several techniques are being tested, and they show great promise in preventing bird fatalities.

  • Paint It Black: Scientists in Norway have discovered a cost-effective way to reduce significantly the number of bird deaths caused by wind turbines. Painting one blade black reduces the motion blue giving the bird passive cues that there is a giant rotating thing in the front, and they need to change their direction. This method helped reduce the number of bird deaths by 70% compared to the turbines that were not painted. Raptors were the greatest benefactor of this technique. There were no white tail eagle carcasses near the turbine after painting it black. If done during the construction, this method doesn’t affect the cost much.
  • Tilling the base – Tilling, the soil around the bottom of the turbine can also deter birds and reduce avian mortality. A study published in the journal of environmental management analysed the deaths of lesser kestrel due to turbine collisions for ten years. The area around the turbine was carefully checked for two years before and after the tilling operation. It was found that this method was able to reduce the kestrel mortally by 75 to 100%. The lack of prey around the turbine discouraged the birds from hunting in a dangerous area, and they eventually move to safer places.
  • Automated Curtailment system: At the top of the world wind power facility in Wyoming, researchers are using A.I. and machine learning to protect birds from wind turbines. In this method, a camera system analyses the flying objects and classifies them as birds or not. It then decides which turbines to curtail to protect the bird. This method reduced the bird mortality rate by 82%. This program is still under development, and much better results are expected in the future.

Wind turbines and bats

Despite all the bad press that bats get, they play a vital role in our ecology. USA and Canada is home to 47 species of bats. These species significantly reduce the number of agricultural pests. It is estimated that they provide services worth $3.7 billion per year. It is the bats that pollinate agave plants. (so there is no tequila without bats!)

Bats live long and reproduce slowly (just one or two pups a year), so they cannot respond to man-made threats fast enough. During the 1990s, the bat’s deaths caused by turbines were not reported, so there is no accurate data for that period.

Most experts agree that hundreds of thousands of bats are killed each year in the united states due to wind turbine collisions. 80% of these deaths comprise three species; hoary bats (38%), eastern red bats (22%) and silver-haired bats (19%). A study published in biological conservation predicted that we could lose about 90% of these in the next 50 years if conservation measures are not implemented on turbines.

Scientists are trying to understand why are bats attracted to wind turbines. The hypothesis says that they are drawn to the sound of the turbine. It can also be the increased number of insects around the blades. Their mating rituals can also be responsible. However, it has been positively established that higher turbines cause a more significant number of bat fatalities.

How to protect Bats from wind turbines

  • Bat deterrent Systems: The bats use echolocation to navigate and find food. They emit high-frequency sounds that bounce off surfaces to let them know what they are. If those frequencies are jammed, they won’t interpret the object and ultimately leave that area. This principle is used to develop bat deterrent system by NRG systems. Researchers from Bat conservation international and Texas state university found that these devices can reduce bat deaths by 54%. These systems are designed to affect only a small area around the turbine and will not cause damage to the bat habitat. According to The research team, a wide range of 3D whistles can be 3D printed to match frequencies of different bat species. A.I. is being employed to analyse bat acoustics to make this system more efficient.
  • Curtaining Wind Turbine Speeds – slower wind turbines kill a lesser number of bats. Studies have found reducing the blade speed to 5m/s can reduce bat deaths by 50%. An excellent way to do it is by feathering the turbine. Feathering is changing the angle of blades in the direction of the wind to reduce the speed. Without feathering, the speeds can easily reach at levels that are very lethal to the bats.

Efforts by authorities to reduce bird and bats deaths by wind turbines

U.S. Fish and Wildlife Service and Wind Turbine Guidelines Advisory Committee developed a set of guidelines to protect various species from wind turbine collisions. These guidelines help developers identify the species in danger like migratory birds and bats, bald and golden eagles, and other raptors. Some vulnerable areas can be excluded entirely from wind projects.

They use a tiered approach to see if wind power is suitable for a particular area and its effect on concerned species. They evaluate a place before, during and after construction and decide the next steps based on data collected. If they find that wind turbine at a particular site is bad for birds and bats, they can abandon the project.

The Bigger Picture

As we have learned, the role of wind power in bird deaths is meagre compared to other human-made sources. However, we are not saying that it makes it okay. Every life is precious and is worth protecting. The wind power industry follows very high safety standards and is constantly working on reducing the damage as much as possible. A lot of creative scientists are working to make wind turbines safer for the birds. We have also to consider global warming. If we continue to rely on fossil fuels, the number of bird deaths will be unimaginable, and many species will completely go extinct. Wind power is still one of the cleanest energy sources and holds great promise in ensuring a cleaner world. We have to be a little more innovative to make it safer for all species.

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