In response to growing accusations from both conservationists and conservatives that renewable energy sources like solar and wind kill too many birds, U.S. News and World Report has compiled data on which energy industries are responsible for the most bird deaths every year.

For each power source — wind, solar, oil and gas, nuclear, and coal — the data on bird deaths is gathered from different advocacy and industry groups, academic institutions, and government sources. Because estimates vary so widely on solar, wind, and oil, U.S. News included both low-range and high-range estimates for how many birds are killed by those electricity sources.

Either way, the results show that even with high-range estimates for renewables compared to low-range estimates for fossil fuels, fossil fuels are responsible for far more bird fatalities than solar or wind. Note the chart below:


A U.S. News and World Report chart shows estimates of how many birds are killed each year by different fuel sources. CREDIT: U.S. News & World Report

The results should be taken with a grain of salt. As U.S. News noted, each study used a different methodology to come up with their numbers. “There’s no standardized way of doing it that everyone can agree to,” Garry George, the renewable energy director for Audubon California, told the magazine.

In addition, some of the research used is outdated, and does not take into account that renewable power stands to increase in the United States. For example, the study used to estimate bird deaths from United States wind power was from 2009, and wind power has increased substantially in the United States since then. According to the American Wind Energy Association, total installed wind capacity in the U.S. was approximately 35,000 megawatts — a number that has increased to about 61,000 for 2014. Those numbers stand to increase as well, as more than 12,000 megawatts of wind capacity were currently under construction at the end of 2013, according to AWEA.

The research also varies by source. Both the low and high estimates of wind power bird deaths came from a peer-reviewed study in the journal Biological Conservation, and was essentially a round-up of all available data peer-reviewed studies on the matter done by other scientists. For oil and gas, both the low and high estimates came from a Bureau of Land Management memo from 2012.

The low estimate for bird deaths from solar power comes from the solar company BrightSource, which was recently accused by the Center for Biological Diversity of operating a solar farm that kills as many as 28,000 birds a year. The high estimate comes from the Center for Biological Diversity, whose estimate is just from that one solar farm in California. Bird deaths from solar farms have been estimated to be relatively low, though — a U.S. Fish and Wildlife study earlier this year found only 233 bird deaths at three different solar farms in California over the course of two years.

As for coal, those bird death numbers came from a peer-reviewed study in the journal Renewable Energy. That estimate had a more sweeping methodology, though, with the study’s author including everything from coal mining to production — and bird deaths from climate change that coal emissions produce. Together, that amounted to about five birds per gigawatt-hour of energy produced by coal, almost 8 million per year.

Either way, U.S. News notes that none of these numbers hold a candle to cats, which are estimated to kill 1.4 to 3.7 billion birds every year.

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