Birds get electrocuted on power lines. But people shooting birds perched on power poles can be more of a problem. In a survey of five sites in the western United States, two-thirds of the birds found dead under power lines were shot.
Avians found dead along power lines are often assumed to have died from electrocution, especially if their bodies show burns or emaciation, said Eve Thomason, a wildlife biologist at Boise State University in Idaho. But the animal may have been injured or killed before being zapped.
“We really need an X-ray to fully understand what might have happened,” said Ms. Thomason, who used to work for a utility that inspects power lines to assess the danger they pose to birds.
In a new study, published Tuesday in the journal iScience, Ms. walked. Thomason and his colleagues along 122 miles of power lines in Idaho, Oregon, Utah and Wyoming, collected 410 bird carcasses. Back in the lab, the researchers X-rayed the birds, looking for evidence of gunshot wounds or other trauma.
“Most of them come back with bullet fragments or shotgun pellets,” said Ms. Thomason. Of the 175 birds for which they determined the cause of death, 66 percent were shot, the scientists reported.
There are anecdotal reports of such shootings. But “this is the first time someone has done a large-scale study at multiple sites to find out if this is a problem,” said Todd Katzner, a research wildlife biologist at the United States Geological Survey in Boise and one of the authors. of learning. . “It’s more widespread than we previously understood,” he said.
Sites vary in the proportion of birds taken, said Libby Mojica, a wildlife biologist and ornithologist at the engineering firm EDM International who was not part of the study. In both areas, all deaths were attributed to gunshots. But in another, shootings accounted for 39 percent of deaths and a similar percentage of deaths were from electricity. It’s unclear how broadly the findings apply, but even the lowest percentage makes for a large number of birds, he said.
The dead birds were mostly crows and raptors, the group that includes eagles, hawks and falcons. Killing these animals is illegal under some US laws. And shootings, including those on power lines, can put populations of some birds, such as golden eagles, at risk.
Illegal hunting is “a major issue that just baffles me,” said Brian Millsap, an ornithologist at New Mexico State University. Dr. Millsap was not part of this study, but he collaborated with Dr. Katzner. “There’s been a ton of work done to prove that raptors aren’t the vermin they’re thought to be,” he said.
With all the effort put into educational campaigns by fish and wildlife agencies, non-governmental organizations and the US Fish and Wildlife Service, the researchers thought the shootings declined.
Electrical utilities that own power poles are responsible for bird deaths from their infrastructure, Ms. Mojica. Some large electrical utilities spend hundreds of thousands of dollars each year to reduce the risk of avian electrocutions. But if the birds are dying because of the crimes, it shifts the blame from the power companies and may mean different conservation actions are needed, he said.
However, electrocutions on power poles remain a problem in some areas, said Dr. Millsap. Recent unpublished work by him and his colleagues found that, in parts of Texas and New Mexico, about 34 percent of golden eagles that survived to leave their nests were electrocuted within their first years of life, he said. That happens in areas where utilities don’t prioritize retrofitting poles to make them safe.
The researchers are expanding their study to Nevada and working to understand what motivates people to shoot the protected birds. But preventing illegal killings is difficult, says Dr. Millsap. Enforcement and prosecution take time, and the approach can be undermined by judges issuing low fines.
However, Pete Marra, an ornithologist at Georgetown University who has studied bird population declines in North America but was not part of this study, said the work is important in the fight against bird extinction. “What is important to stop the decline of birds is to understand what causes the decline of birds,” he said.
