Do wind turbines pose a significant risk to birds and bats? While one might think otherwise, the answer generally is no. In fact, several national studies have shown that the percentage of avian fatalities from wind turbines is actually quite low – estimated at 0.1 percent.
Interestingly, cats, both feral and domestic, are responsible for the vast majority of bird fatalities, killing as many as 3.7 billion birds annually. Buildings and windows are the second biggest culprit, with estimates of avian fatality from these sources up to 1 billion deaths per year. By contrast, wind turbines account for 350 thousand deaths at most. So a bird is about 1,000 times more likely to die striking a building or window, and more than 10,000 times more likely to die by a cat, than from a wind turbine.
Given the importance of birds and bats to the ecosystem, understanding wind/wildlife interactions is a high priority for the wind industry, and one goal of any wind energy project is to plan in a manner that balances energy production with wildlife protection. With this in mind, the U.S. Fish and Wildlife Service created Wind Energy (Siting) Guidelines that call for a “tiered approach” to assessing any potential risk to species of concern and their habitats. The tiered approach provides the opportunity to assess and evaluate risk and impact at each stage of a project, from initial development through post-construction.
At many wind farms special care is taken to help safeguard the bird population during the spring and fall migratory periods. Best practices include reducing any unnecessary lighting at projects and using flashing lights for required tall structure safety.
Reducing interactions with bats requires somewhat different strategies than for birds. Scientists have observed that bats seemed to be attracted to wind turbines in some cases. While the reasons remain unclear, developers have implemented a practice of locating turbines farther from potential bat habitats such as large wooded areas or caves. Further, wind park owners are choosing to modify operations to reduce the likelihood that bats are present during turbine operation. Essentially, this involves increasing the wind speed at which a turbine rotor begins to turn during times of the day and year when bat activity is higher. This means wind project operators are choosing to sacrifice portions of their potential generation in the interest of bat protection.
Given that wind energy is an important and rapidly growing part of the nation’s energy mix, new technologies are being developed to help birds and bats co-exist safely with the turbines. These include using various technologies to identify wildlife near turbines, manage operations accordingly, and in some cases use devices to deter wildlife from coming too close to turbines. Design changes to the turbines themselves are also being considered and thoughtful, well-researched siting and post construction monitoring will remain keys to further improving wind/wildlife interactions.