Bald eagles have made a remarkable recovery across the United States since the pesticide DDT was banned 45 years ago, but the majestic birds are still dying from another environmental poison: lead from bullets and shotgun pellets in wildlife carcasses left behind by hunters.
In New York, which has been a leader in the bald eagle restoration in the Northeast for four decades, state wildlife researchers have documented a growing number of eagle deaths from lead poisoning in recent years. Wildlife rehabilitators have also seen increasing numbers of eagles testing positive for lead in Minnesota, Oregon, Virginia and other states.
The problem is that eagles and other scavengers eat the guts of deer or the carcasses of coyotes, woodchucks and other game shot by hunters. Bits of lead bullets consumed along with the meat break down quickly in an eagle's stomach and enter its bloodstream.
Elevated lead levels cause blindness, paralysis, lack of appetite and neurological problems that make eagles more likely to fly into buildings or vehicles if they don't succumb to lead poisoning first.
Ed Clark, president of the Wildlife Center of Virginia, says they treat 35 to 40 eagles per year find about 60 percent of them have lead in their blood.
"Many hunters don't realize that as much as 50 percent of a bullet may remain in the deer as fragments," he said. "A sliver the size of a grain of rice is enough to kill a bald eagle in 72 hours."
In New York, lead poisoning was confirmed as the cause of death in 38 of 336 bald eagles brought to a Department of Environmental Conservation lab near Albany between 2000 and 2015, said state wildlife biologist Kevin Hynes, who does the necropsies. Nine bald eagles were confirmed as lead-poisoning deaths in 2016, and seven so far this year.
"We've examined over 300 bald eagle carcasses for lead since the mid-1990s, and found 83 percent had some exposure to lead," said Krysten Schuler, a Cornell University wildlife disease ecologist who's collaborating with New York's Department of Environmental Conservation.
Lynn Tompkins, director of the Blue Mountain Wildlife Center in Oregon, said more than 75 percent of the eagles brought to her rehabilitation clinic have some level of lead. "We lost two this year with incredibly high levels," she added.
"We're getting more eagle deaths overall because the eagle population has increased," Hynes said. When state biologists launched a restoration program in 1976, hand-rearing baby eagles captured in Alaska and releasing them in New York, there were no reproducing bald eagles in the state. This year, New York's bald eagle population hit a record-breaking 323 breeding pairs.
While lead poisoning clearly isn't threatening the eagle population as a whole, the impact on individual birds is worrisome, Hynes said.
The Humane Society of the United States has long sought restrictions on lead ammunition, beyond the 1991 federal ban on lead shot for waterfowl hunting. California is the first state to ban hunting with lead bullets, phasing out such ammunition by 2019 in favor of less-toxic copper or steel.
On former President Barack Obama's last day in office, Fish and Wildlife Service Director Dan Ashe signed an order calling for phase-out of lead ammunition on federal lands by 2022. But President Donald Trump's new Secretary of the Interior, Ryan Zinke, reversed Ashe's order on his first day in office.
Such restrictions are vehemently opposed by the National Rifle Association and other hunting and gun rights organizations.
"Eagles are doing very well, their recovery is a great success story largely supported by excise taxes paid by hunters" on lead ammunition and guns, said Lawrence Keane, senior vice president of the National Shooting Sports Association.
Copper bullets, the main alternative to lead, are more expensive and harder to find than traditional ones. There's also a debate over whether they perform as well.
Virginia wildlife advocate Clark said that rather than a ban on lead ammunition, his group is seeking a public education campaign so hunters are aware of the problem and how they can help.
"It can be easily solved by not leaving the remains of animals where scavengers can get to them, or to simply use non-lead ammunition," he said. "This information needs to be in every hunter safety course."