The bald eagle, whose resurgence is considered one of the great conservation success stories of the 21st century, faces a serious threat: lead poisoning.
Researchers who tested the feathers, bones, livers and blood of 1,200 bald eagles and golden eagles, another bird of prey in the Northern Hemisphere, found that nearly half of them had been repeatedly exposed to lead, which can lead to death and slow population growth. .
Scientists believe the lead’s primary source is the used ammunition from hunters who shoot animals that prey on eagles, usually in winter, according to the study, published Thursday in the journal Science.
Nearly a third of the birds tested also showed signs of acute poisoning, or short-term exposure to lead, according to the study, which was led by scientists at the United States Geological Survey, Conservation Science Global, Inc. and the US Fish and Pet Service.
The effects of lead poisoning are devastating, said Vincent A. Slabe, the study’s lead author and a conservation research biologist for Conservation Science Global in Montana.
Lead poisoning can prevent an eagle from properly digesting food, eventually leading to starvation, he said. It can cause such severe loss of locomotion that an eagle not only loses the ability to fly, but to move at all, he said.
“Lead can affect every system of an eagle’s body — their respiratory system, their digestive system, their reproductive system,” said Dr. bib.
The study, which examined bald eagles and golden eagles from 38 states, is the first to look at the effects of lead poisoning on bird populations on such a large scale, said Todd E. Katzner, a research wildlife biologist with the US Geological Survey. †
The study also found that poisoning slowed population growth by about 4 percent for bald eagles and 1 percent for golden eagles, which amounts to about 35,000. The population of bald eagles now exceeds 300,000, according to researchers.
“These percentages seem small, but over time, thousands and thousands of individual birds are removed from the population” because of lead poisoning, said Dr. katzner.
Bald eagles had been largely killed off decades ago by the widespread use of the synthetic insecticide DDT. A 1972 ban on DDT and conservation efforts helped restore the population, with the bald eagle being removed from protection under the Endangered Species Act in 2007.
dr. Slabe said he hoped the report’s findings would help educate fighters and encourage more of them to switch to lead-free ammunition.
“This is 100 percent man-made and completely preventable,” said Laura Hale, president of Badger Run Wildlife Rehab in Klamath Falls, Oregon, whose organization has rescued bald eagles, golden eagles and several species of hawks. were poisoned by lead.
In 2018, the group attempted to rescue an eagle found by a hunter in the woods, unable to fly and gasping for air. When Mrs. Hale told the hunter that the eagle most likely got sick from eating contaminated gut stocks – the remains left after a hunter stripped the animal’s carcass of its flesh – she said it was affected.
“He was shocked,” recalls Mrs. Hale. “He wanted to stop hunting.”
Mrs. Hale said she told him not to stop hunting; all he had to do was stop using lead ammunition.
Concerned about the effects not only on wildlife but also on game meat consumed by humans, many hunters have moved away from lead ammunition and started using copper bullets.
Sporting Lead-Free, a Wyoming-based hunting and fishing group working to raise awareness about the ill effects of lead munitions, posted a short film with testimonials from hunters who quit.
“Hunters are conservationists,” said Bryan Bedrosian, Sporting Lead-Free co-founder and raptor biologist. “This doesn’t have to be a polarizing problem.”
Some fighters are hesitant to switch ammunition because of tradition, a mistaken belief that copper bullets are less effective, or because they have a backlog of lead bullets, he said.
“Then there are still people who just don’t know,” said Mr Bedrosian, who says he uses lead bullets at the firing range, where he knows the ammunition will not come into contact with wildlife.
Hannah Leonard, the group’s outreach coordinator, said she was hunting with lead bullets until four years ago, when she encountered an emaciated golden eagle stumbling on the ground while hunting in Anaconda, Mont.
“Her claws were really clenched, her wings were hanging down,” said Mrs. Leonard. “You could tell she was in danger.”
The eagle later died, and Mrs. Leonard said the animal rescue group she called to try to save the bird told her the cause of death was lead poisoning.
“It was a no-brainer for me to switch ammunition,” she said.
In January 2017, the U.S. Fish and Wildlife Service issued a policy to phase out the use of lead munitions and fishing tackle used in national wildlife refuges, one of the latest moves by the Obama administration. The Trump administration reversed the decision less than two months later.
On Friday, the agency declined to say whether those policies would be reinstated as a result of the new study.
According to the agency, there has been a nationwide ban on the use of lead shot for hunting waterfowl since 1991.
California has banned the use of lead munitions statewide, including on federal land, largely to prevent lead’s ill effects on the endangered California condor.
“The U.S. Fish and Wildlife Service uses the best available scientific data to maintain wildlife populations and evaluate compatible uses on the land we manage, as well as under applicable local, state, and federal laws,” Vanessa Kauffman , an agency spokeswoman, said Friday.
dr. Slabe said that once they were trained, hunters would voluntarily stop using lead ammunition.
“Hunters are very receptive to this issue,” he said. “Hunters are the solution to this problem.”