Finally, the last major concern of wind farms is the killing of birds. From a survey from California performed by California Energy Commission in 2004 demonstrate that approximately 4,700 birds are killed each year at Altamont Pass. And about 1,300 of those birds are birds of preys. Wind turbines not only kill birds but they also kill lots of bats. A study conducted in 2004, at two US eastern wind farm, have found that the 63 turbines have killed more than 2200 bats within 6 weeks and have showed that these wind farm are dangerous for bat population. On the contrary, some study indicate that the killing of birds from turbines are insignificant compared to other human activities like traffic, hunting, power lines, tall buildings and pollution caused from the burning of fossils fuel. For example, a study in the United Kingdom (UK) conducted by the Royal Society for Protection of Birds (RSPB) showed that about 1 bird is killed per turbine annually whereas about 10 millions birds were killed by cars. Another study, shows us that migrating bird are a lot smarter than we think and can fly through wind turbines easily without the need to changing their route. They have concluded that good positioning of wind turbine will not endanger the birds and that climate change is a much greater threat to birds and to other living species. They therefore support wind energy. Figure 5 is a bar chart that compares the deaths of birds from wind farm and those from human structures in the US annually. We can see that wind turbines are not the major cause of bird fatalities with only 0.1-0.2% comparatively to the other structures.
Percentage of Annual Bird Fatalities by Source
The above graph needs to be corrected to show the source by number of birds. That is to say, the number of birds per building vs the number of birds per wind turbine. There are more buildings in the world than turbines.
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