By: Kyle Xu

Many people know of the threats that power lines can pose to birds. But what people don’t know is that electrocution isn’t the only way that they die.

In a survey of five sites in the western United States, two-thirds of the birds found dead had been shot and brutally killed.

“We really need X-rays to understand fully what may have happened,” said Eve Thomason, a wildlife biologist at Boise State University in Idaho. Thomason says that most dead birds found along power lines are assumed to have been electrocuted, especially if they have scorch marks or singeing. But they may have been injured or shot before being zapped.

In the new study, published on Tuesday, Thomason and her colleagues walked 122 miles in search of dead birds, picking up 410 avian carcasses. Back in the lab, her team X-rayed the birds, looking for gunshot wounds.

Out of the 410 birds, 175 died arbitrarily. Out of those 175 birds, 66 percent had been shot, with Thomason finding bullet fragments or shotgun pellets.

The dead birds were mostly ravens and raptors, with the group also including eagles, hawks, and falcons. Killing these animals is illegal under the Migratory Bird Treaty Act. And these shootings may put some already dwindling bird populations in danger.

Illegal shootings are described as “an overriding issue that just perplexes the heck out of me,” said Brian Millsap, an ornithologist at New Mexico State University who was not part of the study. “There’s just been a ton of work done to get the word out that raptors aren’t the vermin that they were thought to be,” he said.

The researchers are continuing to forward their study into Nevada, trying to find out what motivates people to kill harmless birds. Nonetheless, “What’s essential in order to stop the declines of birds is to understand what’s causing the declines of birds,” said Pete Marra, an ornithologist at Georgetown University.