The bald eagle, whose resurgence is considered one of the great conservation successes of the 21st century, faces a serious threat: lead poisoning.
Researchers who tested the feathers, bones, liver and blood of 1,200 bald eagles and golden eagles, another northern hemisphere bird of prey, found that almost half of them had been repeatedly exposed to lead, which can cause death and slow population growth. .
According to the study published Thursday in the journal Science, scientists believe the main source of lead comes from spent ammunition from hunters who shoot the animals that the eagles then scavenge, usually during the winter.
Nearly a third of birds tested also showed signs of acute poisoning or short-term lead exposure, according to the study, which was conducted by scientists from the United States Geological Survey, Conservation Science Global , Inc. and the US Fish and Wildlife Service.
The effects of lead poisoning are devastating, said Vincent A. Slabe, the study’s lead author and a research wildlife biologist for Conservation Science Global in Montana.
Lead poisoning can prevent an eagle from digesting food properly, which can eventually lead to starvation, he said. This can lead to a loss of locomotion so severe that an eagle will lose the ability not only to fly, but to move at all, he said.
“Lead can affect every system in an eagle’s body – their respiratory system, their digestive system, their reproductive system,” Dr Slabe said.
The study, which examined bald eagles and golden eagles from 38 states, is the first to examine the effects of lead poisoning on bird populations on such a large scale, said Todd E. Katzner, wildlife biology researcher at the US Geological Survey. .
Research also showed that poisoning slowed population growth rates by around 4% for bald eagles and 1% for golden eagles, which number around 35,000. bald eagles is now over 300,000, according to researchers.
“These percentages seem small, but over time thousands upon thousands of individual birds are removed from the population” due to lead poisoning, Dr. Katzner said.
Decades ago, bald eagles were largely killed by the widespread use of the synthetic insecticide DDT. A DDT ban in 1972 and conservation efforts helped the population rebound, with the bald eagle being removed from Endangered Species Act protection in 2007.
Dr Slabe said he hoped the report’s findings would help educate hunters and encourage more of them to switch to lead-free ammunition.
“It’s 100% man-made and totally preventable,” said Laura Hale, president of Badger Run Wildlife Rehab in Klamath Falls, Oregon, whose organization has taken in bald eagles, golden eagles and different species. of falcons that have been poisoned by lead.
In 2018, the group attempted to rescue an eagle that a hunter had found in the woods and was flightless and out of breath. When Ms Hale told the hunter the eagle had most likely fallen ill from feeding on piles of contaminated intestines – the remains left behind after a hunter stripped the animal’s carcass of its meat – she said that he was reached.
“He was horrified,” Ms Hale recalled. “He wanted to stop hunting.”
Mrs. Hale said she told him he didn’t have to stop hunting; he just had to stop using lead ammunition.
Many hunters, concerned about the effects not only on wildlife but also on game meat consumed by humans, moved away from lead ammunition and started using copper bullets.
Sporting Lead-Free, a Wyoming-based group of hunters and anglers that seeks to raise awareness of the harmful effects of lead ammunition, released a short film with testimonials from hunters who have stopped using them.
“Hunters are conservationists,” said Bryan Bedrosian, Sporting Lead-Free co-founder and raptor biologist. “It doesn’t have to be a polarizing issue.”
Some hunters are reluctant to switch ammunition because of tradition, a misguided 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 on the range, where he knows the ammunition won’t come in. contact with wildlife.
Hannah Leonard, the group’s outreach coordinator, said she hunted with lead bullets until four years ago when she came across an emaciated golden eagle hobbling on the ground as she hunted in Anaconda, Montana.
“His talons were really tight, his wings were drooping,” Ms Leonard said. “You could tell she was in danger.”
The eagle later died and Ms 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 change” the type of ammunition, she said.
In January 2017, the U.S. Fish and Wildlife Service released a policy to phase out the use of lead ammunition and fishing gear used in National Wildlife Refuges, one of the latest acts of the Obama administration. . The Trump administration reversed its decision less than two months later.
On Friday, the service declined to say whether that policy would be reinstated following the new study.
There has been a nationwide ban on the use of lead shot for waterfowl hunting since 1991, according to the service.
California bans the use of lead ammunition statewide, including on federal lands, largely to prevent the harmful effects of lead on the endangered California condor.
“The U.S. Fish and Wildlife Service uses the best available science to conserve wildlife populations and assess compatible uses on the lands we administer, as well as under applicable local, state, and federal laws,” Vanessa Kauffman , spokesman for the agency, said Friday.
Dr Slabe said hunters, once educated, would voluntarily stop using lead ammunition.
“Hunters are very receptive to this question,” he said. “Hunters are the solution to this problem.”