It has been claimed that due to their large size, and the velocity of their blades that wind turbines kill large numbers of birds that run into them at night, or in fog, and die.


Do wind turbines kill many birds each year?

  • It has been claimed where? – user7920 Nov 26 '12 at 7:33
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    @cole, I have heard this claim too, but I'm not able to find anything on this fact in English language. – Carlo Alterego Nov 26 '12 at 8:08
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    Google makes it easy to find the claim all over the place. It also provides good sources, making the question a little less fruitful. – Flimzy Nov 26 '12 at 8:23
  • true. birds must be quite blind at night otherwise its hard to comprehend how they can miss it – Clatoon Adour Nov 26 '12 at 8:46
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    @ClatoonAdour - The blades rotate at about 50 mph and are mostly open space. Bird brains are not equipped to handle these types of hazards in their flight path. I watched an entire flock of sparrows fly through it the blades cut 2 paths right through the flock. I live in central IL where we have about 1000 of them in 20 different sites with in 100 miles of me. – Chad Nov 26 '12 at 14:22

Do wind turbines kill many birds each year?

In short:

An upper estimate might be of the order of half a million birds per year in the USA.

However it seems that hundreds of millions of birds are killed by collisions with other man-made structures. So wind turbines account for a small percentage of bird deaths attributable to human activity.

Nevertheless this can be a significant threat to the survival of some important bird species.

at night, or in fog

Wind turbines are hazard to birds (and other avians) in daylight. Bird evolution has evidently not incuded the necessary millions of years of exposure to non-catastrophic levels of threat from this type of fast-moving hazard. They are poorly equipped cognitively to recognise danger in any of these and other man-made hazards.

Per small installation

Some individual wind-turbine operators think even ten deaths per year per turbine is too many:

Primary school forced to turn off wind turbine after bird deaths

"We were told by the manufacturer to expect maybe one fatality a year but it killed 14 in six months so we took advice and made the decision to turn it off. "If it had happened at night time you could understand that the birds couldn't see the blades, which rotate at 135mph but it was happening at all different times of the day."

2002 Study

Large numbers of birds die every year from other causes, turbine-related deaths are currently alleged to be only a very small proportion of these.

According to a 2002 study A Summary and Comparison of Bird Mortality from Anthropogenic Causes with an Emphasis on Collisions "funded by DOE, with direction and support from the Wildlife Working Group of the National Wind Coordinating Committee"

  • Collisions with buildings kill 550 million birds each year,
  • Cats kill 100 million birds each year,
  • Collisions with wind turbines kill 28,500 birds each year.

So the answer to the question depends on how many is "many".

2016 study

More recent studies find higher numbers of avian deaths per year.

A 2016 study A preliminary assessment of avian mortality at utility-scale solar energy facilities in the United States included this table:

Table 2.

Estimated annual avian mortality from various sources 
in the Southern California Region and United States.

Mortality source                 Southern California    United States
Utility-scale solar energy 
(USSE) developments              16,200–59,400         37,800–138,600 a

Wind energy developments         29,537–48,862         140,000–573,000 b

Fossil fuel power plants         3,561,600             14.5 million c

Communication towers             70,552                4.5–6.8 million d

Roadway vehicles                 >453,000e             89–340 million f

Buildings and windows            >7,800,000g           365–988 million h

a   Based on approximately 14 GW total name plate capacity of   
    utility-scale solar facilities in operations or under construction  
    across the United States [7].
b   Sources: Loss et al. [36], Smallwood [23], Erickson et al. [24].  
c   Source: Sovacool [25].  
d   Sources: Erickson et al. (2005), Longcore et al. [33].  
e   Represents a minimum estimate using only estimated mortality for   
    paved roadways in the southern California study region.
f   Source: Loss et al. [49].  
g   Represents a minimum estimate using only estimated mortality   
    for residential structures in the southern California study region.  
h   Source: Loss et al. [34].

I have not checked the dates of the references. It may be that this 2016 study is based on data from older studies.

Effects on endangered species

Deaths for some bird species may be more significant than others: Scientists study wind-farm risks to birds

One survey at Big Horn Wind Farm in Klickitat County estimated that more than 30 raptors were killed during an initial year of operations — more than seven times the number forecast in a pre-construction study. The dead raptors included kestrels, red-tailed hawks, short-eared owls and a ferruginous hawk, which Washington state lists as a threatened species.

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    Considering there are more buildings than turbines, it would be interesting to see what the "per capita" type figures would be, if it would make a difference or not. – whatsisname Nov 27 '12 at 4:00
  • Maybe we should do something about all those buildings. Take them down, maybe. – user29285 May 13 '16 at 1:10
  • Have you considered updating this answer? -- Even assuming the presentation is not biased for the DOE-funded Power-industry-written paper you link, it was published in 2002-5 and likely uses data even older than that -- Orders of magnitude more wind turbines have been constructed since then and I'll guess the increase in death rate is at least linear with the increase in turbines. – user23715 Apr 25 '17 at 23:16
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    @user23715: You make some good points and I would like to update the answer. I just need to find some recent good quality scientific studies that address the question. – RedGrittyBrick Apr 26 '17 at 13:54
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    Birds have trouble predicting the rotation of the blades, which is a change in direction. Wind turbines also affect different species of birds very differently and they affect them differently than buildings do. So if bird deaths are merely "an issue" or if they are "a serious issue" depends strongly on the location of the turbine. That's why in several jurisdictions scouts need to visit the location and estimate the impact, and possibly recommend seasonal time outs for the turbine, before a turbine can be built. – Peter May 12 '17 at 18:59

The simple answer is yes. The more complex answer is that the number of deaths is nothing in comparison to other man made structures and the risks from climate change.

There have been several studies done to find the environmental impact of wind farms on birds. Generally birds lack the ability to dodge humans and their quest for global supremacy. From the American Bird Conservancy there are a list of deaths related to sources as deaths per year in the US:

Feral and domestic cats - Hundreds of millions

Power lines - 130-174 million

Windows - 100 million to 1 billion (NB the high end seems too large to me)

Pesticides - 70 million

Cars - 60-80 million

Lighted communication towers - 40-50 million

Wind turbines - 10-40,000 (Table found here)

Obviously wind turbines aren't as popular as cars, cats and windows, but with the expected increase in wind energy generation, the impacts will likely increase. The thing that has to be borne in mind is that the wind turbines are on an order of magnitude smaller impact than other bird killers. It also has to be remembered that the studies are also showing that newer wind power plants are having less impact on birds due to design upgrades, better placement and better ecological planning.

The real issue here is climate change. Coal power plants kill birds, in fact, they are threatening to wipe out entire species. According to a study reported in Scientific American, at least 950 entire species of terrestrial birds will be threatened with extinction as a result of climate change under several scenarios, even at the lower estimate of temperature gains, just counting species of non-sea birds in the higher latitudes; outside the tropics. Birds in the tropics will be impacted by habitat loss, which brings the total species wiped out to ~1800 (Jetz, Wilcove, and Dobson 2007).

The take home point is that we need clean energy sources to save bird species. Those that fly into turbines each year will be minimised with better designs and locations of turbines. In the meantime, worry about the cats and climate change.

Update: recent studies have shown that birds of prey are more prone to injury and death from wind turbines. Essentially, birds of prey spend a lot of time looking down for prey and not enough time looking where they are going. The usual bird collision rate is 0.08 birds per turbine per day on average (range 0.05–0.19), whilst the 'smarter' Eagles are colliding at a rate of 0.112 to 0.133. The study also suggests that bird size and speed of flight are important determinants of collision rates, hence why gliding and hovering prey birds are colliding more often. It is worth bearing in mind that both of these collision rates (that often result in death) still indicate an avoidance rate of 99%.

This avoidance rate is important to compare to the relative deaths per gigawatt-hour of the power sources to realise that wind power is still a very good option. This study estimates that wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour of electricity while fossil-fueled power stations are responsible for about 5.2 fatalities per gigawatt-hour. Thus, wind turbines could do with some investigation into how to make them safer for birds, but they are already a much better option than fossil fuels.

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