Some opponents of wind energy claim that the spinning rotors of wind turbines kill a large number of birds. In 2018, U.S. Department of Interior Secretary Ryan Zinke said that “…wind chops up birds.”1 In 2020, President Donald Trump stated that wind energy “…kills all the birds…You want to see a bird graveyard? Go under a windmill someday. You’ll see more birds than you’ve ever seen in your life.”2 Similarly, an environmental group in the United Kingdom claimed that “we are many years into discovering that these bloody machines kill birds in large numbers.”3
Is this a legitimate concern? There are two ways to investigate this question. The first is to look at the question in an absolute sense: how many birds are killed by wind turbines? On this point the most reliable data are very clear: fatalities from wind turbines are way down on the list of anthropogenic causes.4
In the United States, free-ranging domestic cats kill 1.3–4.0 billion birds annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality.5 The next deadliest killer is a collision with buildings, especially those with lots of glass, which kills from 100 million to 1 billion birds each year in the United States.6 Reflective glass may create the illusion of a clear path, or the transparency of some glass makes it difficult to interpret as a solid barrier. Mortality from collisions with wind turbines is several orders of magnitude lower than the leading causes of death (hundreds of thousands compared to hundreds of millions).
The same data can be interpreted in a slightly different way. Cats cause about 1 in every 1.4 bird deaths from anthropogenic causes, collisions with motor vehicles cause 1 in 16, electrocutions cause one in 594, while collisions with onshore wind turbines cause about one in every 14,000 deaths.
The other way to view the problem is in a relative sense. This involves comparing wind turbines to other sources of energy in terms of their impact on bird mortality. An early analysis with limited data suggested that fossil fuel power plants kill more birds per kWh of electricity generated compared to wind.7 However, there is no recent comprehensive analysis that compares different forms of electricity generation across the entire supply chain.
On this point, the data presented above provides one insight. Oil pits-just one stop on the oil supply chain-are themselves a major hazard to birds (and other wildlife). Such pits contain waste fluids produced from oil production that are comprised of oil, water, salts, and other chemicals that are stored in on-site ponds or that are transported to large commercial evaporation ponds for disposal.8 Birds may be attracted to the glimmering surface of the pits, mistaking them for lakes and wetlands that provide food, water, safety, and places to rest.
There are several important caveats to the data presented here. First, there is a widely recognized need for a more up-to-date, rigorous analysis of the impact of wind energy on birds and other wildlife.9 For example, recent research indicates that some bird deaths in the western United States that have been attributed to electrocution by power lines were caused by illegal shooting.10 There is a lot of uncertainty to resolve.
Second, we know little about the impact of wind energy on individual populations and species of birds. The data presented here are highly aggregated. Recent work on wind and solar energy facilities in California indicates that specific populations and species of birds are highly vulnerable to the effects of fatalities at renewable energy facilities.11
Third, new wind energy capacity is growing at a very rapid pace which increases the threat to birds. Some of the data presented are more than a decade old when wind energy played a much smaller role in our energy system. Careful attention must be paid to the siting, construction, operation, monitoring, and decommissioning of wind projects.12 It is particularly important to locate facilities away from important migration routes and important feeding, breeding, and roosting habitats of vulnerable bird populations.
Fourth, a wind farm-or any disturbance of habitat-may have indirect effects by forcing bird populations to move from a preferred habitat.11
Fifth, we lack sufficient knowledge to place the data presented here in the context of known large-scale anthropogenic drivers of bird mortality such as the degradation and conversion of habitat due to land cover and land-use change; hunting and trapping; the impact of invasive alien species and disease; pollution of all types; and the effects climate change.
Birds support human well-being through their provision of ecosystem services such as pollination, pest control, nutrient cycling, biodiversity maintenance, ecotourism and recreation, and a wide range of cultural and aesthetic services.13
This vital support is at risk because about one-half of bird species worldwide (5,245) are known or suspected to be undergoing population declines due to human activity, largely habit conversion or degradation.14 Wind energy has substantial environmental benefits related to electricity generated from fossil fuels. Notably, the greenhouse gas intensity of electricity from wind is 37 (natural gas) to 77 (coal) times lower than fossil fuels, and four times lower than biopower.15 However, responsible deployment of wind energy requires careful attention to the potential impact on birds and other wildlife.
1 Ryan Zinke Worries Wind Turbines Kill Birds. His Agency Just Made It Easier, Huffington Post, March 18, 2018, Link
2 Trump Claims Wind Power ‘Kills All Birds,’ But This Chart Shows That’s Not True, Newsweek, October 13, 2020, Link
3 Daily Mail, October 6, 2013, Link
4 United States Fish and Wildlife Service, “Threats to Birds | U.S. Fish & Wildlife Service,” May 25, 2016. https://www.fws.gov/library/collections/threats-birds.
5 Loss, Scott R., Tom Will, and Peter P. Marra. “The Impact of Free-Ranging Domestic Cats on Wildlife of the United States.” Nature Communications 4, no. 1 (January 29, 2013): 1396. https://doi.org/10.1038/ncomms2380.
6 Loss, Scott R., Tom Will, Sara S. Loss, and Peter P. Marra. “Bird–Building Collisions in the United States: Estimates of Annual Mortality and Species Vulnerability.” The Condor 116, no. 1 (January 2014): 8–23. https://doi.org/10.1650/CONDOR-13-090.1.
7 Sovacool, Benjamin K. “Contextualizing Avian Mortality: A Preliminary Appraisal of Bird and Bat Fatalities from Wind, Fossil-Fuel, and Nuclear Electricity.” Energy Policy, China Energy Efficiency, 37, no. 6 (June 1, 2009): 2241–48. https://doi.org/10.1016/j.enpol.2009.02.011.
8 Trail, Pepper W. “Avian Mortality at Oil Pits in the United States: A Review of the Problem and Efforts for Its Solution.” Environmental Management 38, no. 4 (October 1, 2006): 532–44. https://doi.org/10.1007/s00267-005-0201-7.
9 Lowe, Joe. “How Many Birds Are Killed by Wind Turbines?” American Bird Conservancy, January 26, 2021. https://abcbirds.org/blog21/wind-turbine-mortality/.
10 Thomason, Eve C., Natalie J. S. Turley, James R. Belthoff, Tara J. Conkling, and Todd E. Katzner. “Illegal Shooting Is Now a Leading Cause of Death of Birds along Power Lines in the Western USA.” iScience 26, no. 8 (August 18, 2023). https://doi.org/10.1016/j.isci.2023.107274.
11 Conkling, Tara J., Hannah B. Vander Zanden, Taber D. Allison, Jay E. Diffendorfer, Thomas V. Dietsch, Adam E. Duerr, Amy L. Fesnock, et al. “Vulnerability of Avian Populations to Renewable Energy Production.” Royal Society Open Science 9, no. 3 (March 30, 2022): 211558. https://doi.org/10.1098/rsos.211558.
12 Allison, Taber D, Jay E Diffendorfer, Erin F Baerwald, Julie A Beston, David Drake, Amanda M Hale, Cris D Hein, et al. “IMPACTS TO WILDLIFE OF WIND ENERGY SITING AND OPERATION IN THE UNITED STATES.” Issues in Ecology. Ecological Society of America, 2019 Link
13 Whelan, Christopher J., Daniel G. Wenny, and Robert J. Marquis. “Ecosystem Services Provided by Birds.” Annals of the New York Academy of Sciences 1134, no. 1 (2008): 25–60. https://doi.org/10.1196/annals.1439.003.
14 Lees, Alexander C., Lucy Haskell, Tris Allinson, Simeon B. Bezeng, Ian J. Burfield, Luis Miguel Renjifo, Kenneth V. Rosenberg, Ashwin Viswanathan, and Stuart H.M. Butchart. “State of the World’s Birds.” Annual Review of Environment and Resources 47, no. 1 (2022): 231–60. https://doi.org/10.1146/annurev-environ-112420-014642.
15 National Renewable Energy Laboratory, “Life Cycle Greenhouse Gas Emissions from Electricity Generation: Update,” September 2021, https://www.nrel.gov/docs/fy21osti/80580.pdf
