Over the last month, I've spent time in 40 clean energy opposition Facebook groups. In this reporting, I've seen one argument over and over: Wind turbines kill birds. I’ve seen dozens of images of birds killed by wind turbines and links to studies on the topic.

As I've written, these images and posts can have real world impacts. They change voters’ minds. And they can turn clean energy supporters into passionate opponents.

But there's a problem with the bird argument. It fails to put the number of birds killed by wind turbines in context. Given that wind energy is an alternative to fossil fuel energy, we have to ask: How many birds do fossil fuel power plants kill?

In 2012, researchers at Vermont Law School set out to answer this question. They found that wind turbines kill 0.27 birds per gigawatt-hour (GWh). Fossil fuel power plants by comparison kill a staggering 9.4 fatalities per GWh. In other words, fossil fuel power plants kill 35x more birds per unit of electricity than wind turbines.

So how do fossil fuel power plants kill birds?

First, mining for coal and other fossil fuels requires activities like mountaintop removal. This results in habitat loss.

Then, burning these fossil fuels causes acid rain, which directly and indirectly harms birds. As an example, a 2002 study found that acid rain caused the wood thrush population to decline in the United States by 2% to 5%.

Lastly, fossil fuel pollution causes climate change, which is "the single greatest long-term threat to birds and other avian wildlife." According to the IPPC, 12% of birds are at significant risk of global extinction.

All of this led the author of the study to conclude, "The wider use of wind energy can save wildlife and birds as it displaces more harmful sources of electricity."

Or put another way, the best way to protect birds is to displace fossil fuels. And today, wind energy is an inexpensive, environmentally-friendly way to do that.