By: Qinwei Wu

It’s common to think that birds found dead below power lines died from electrocution, but this is not always the case.

A new study published on Tuesday in the journal iScience found that two-thirds of birds that were dead under power lines had been shot beforehand. Eve Tomason, a wildlife biologist at Boise State University, and her colleagues, walked through 122 miles of power lines in Idaho, Oregon, Utah, and Wyoming, collecting 410 dead birds.

After the researchers x-rayed the birds in the lab, Tomason said, “Most of them were coming back with bullet fragments in them or shotgun pellets.” This suggests the birds have been injured or killed before getting electrocuted.

Of the 175 birds for which the researchers were able to determine a cause of death, 66% had been shot. A research wildlife biologist at the United States Geological Survey in Boise, Todd Katzner, an author of the study, noted that “this is the first time somebody has done a large-scale study at multiple sites to figure out if this is a problem,” as there were only a few unreliable cases of such shootings.

Most of the dead birds were ravens a raptors, but some of them are were eagles, hawks, or even falcons. Under several US laws, killing these birds is illegal, and shootings could place birds, like golden eagles, in danger.

Electrical utilities are blamed for bird deaths, and the electrical companies spend hundreds of thousands of dollars per year to reduce this risk. But if most of these birds are dying because of shooters, then this could shift the blame away from the power companies. Still, power lines are a problem.

Brian Millsap, an ornithologist at New Mexico State University, said that 34 percent of golden eagles that survive to leave their nests are electrocuted within their first year of life.

Now, researchers in Nevada are working to understand why people shoot birds. Nonetheless, preventing illegal shootings is very challenging.