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?
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.
Update #2: an Australian researcher has recently done an interview on Ockham’s Razor (an ABC science show) to dispel some of the bird myths surrounding wind turbines.
Update #3: Teale commented via Facebook that the upscaling of power generation by wind hasn’t really changed the annual bird deaths per MW/hr despite the increase in the number of wind turbines and areas with wind farms. The bird deaths are ~33,000 pa, which is still in the range cited by the American Bird Conservationists from a few years ago, and the power generated has increased to ~4%. Again we come back to the point above about what other power generation and mining does to birds is a much larger impact. Remove them and the wind turbines can get a lot more prevalent and still not have the same impact. (NB: there may be some circular referencing going on between the sources in this article, so if this is the case, please send through any revised data sources, especially on data changes with time).