Wind energy is one of the most promising sources of renewable energy out there. Land-based wind farms generate essentially no pollution and have more overall energy-producing and money-saving potential than solar farms. If wind energy has downsides, they are that the turbines cost a lot to build, and that they kill birds. Or at least that's the story.
But how many birds do wind turbines really kill? And is it appreciably more than other sources of power? According to recent research, stats on the number of birds killed annually by collisions with giant, spinning wind turbines is either ambiguous or lower than one might imagine, given the fact that bird-killing is one of the top on the "Cons" side of the "Should We Build a Bunch of Wind Farms To Combat Climate Change?" pros-and-cons list.
One 2011 study found there's really no telling how many birds are actually taken out by wind turbines, since bird mortalities seem to differ so much between wind farms — suggesting that the location of the farms might have more to do with how many birds they kill than the fact of the turbines themselves. The study examined bird data for various sites before and after the construction of the facilities, and found a weak relationship between how many birds they predicted would die as a result of the wind farm, and the actual mortalities.
A 2013 study found that bird mortality from wind turbines actually differs from place to place (at least in Canada, where the research was conducted) and between species, while a 2009 study found that although, sure, wind turbines might kill some flying vertebrates, the numbers couldn't possibly hold a candle to the bird and bat fatalities caused by other forms of power generation. That study estimates that while U.S. wind farms were responsible for the deaths of about 7,000 birds in 2006, nuclear plants killed around 327,000 and fossil-fueled power plants 14.5 million. The researchers broke up the data proportionally, finding that while each gigawatt-hour (GWh) of energy produced by a wind farm was associated with 0.3 fatalities, about 5.2 birds would die at a fossil-fuel facility for the same amount of energy produced.