Since the start of the year, five bald eagles rescued from five Maine towns have been found with elevated levels of lead in their bloodstreams.

They were discovered floundering on the ground, injured and disoriented. One used its wings like they were crutches, but was too weak to fly. Another lay helpless near a frozen riverbank. All five had to be euthanized.

Experts say this is the byproduct of lead bullets used by hunters. The bullets shatter into tiny particles that are often invisible to the naked eye, but can lodge in carcasses, meat or gut piles, which hungry eagles swoop down to consume during the winter.

The lead-poisoning of eagles and other wildlife has emerged as a nationwide issue facing conservation groups and state wildlife managers.

In response, staff at the Maine Department of Inland Fisheries and Wildlife say they are in the early stages of planning a campaign to encourage hunters to use lead-free ammunition made entirely of copper. The Sportsman’s Alliance of Maine is also in talks to sign on to the campaign and distribute information to its members, who are strong proponents of conservation, said the group’s executive director, David Trahan.

“Despite the fact that the bald eagle population is healthy, Maine Inland Fisheries and Wildlife is concerned and recognizes that cases of bald eagle exposure to spent lead ammunition is an issue,” said IFW raptor biologist Erynn Call. “Consequently, the department has joined a regional partnership to minimize the unintended impacts of lead on wildlife.”

IFW wants to work with North American Non-lead Partnership, which currently collaborates with state fish and wildlife departments in Arizona, Utah and Oregon, in addition to several non-government fish and game groups in the South and Southwest.

During warmer months, eagles in Maine prefer to eat fish and small animals, but in winter, when the state’s ponds and rivers freeze over, the majestic birds are left to look for scraps, often found in the piles of entrails left when hunters dress their trophies in the field, or where a game carcass is disposed of outdoors or its meat used as bait.

Once inside the bird’s body, the heavy metal can wreak havoc on its central nervous system, damage internal organs and diminish brain function. Humans suffer the same effects, but a far smaller amount of lead can prove fatal to a bird.

In Maine, as the state’s eagle population grew from 30 breeding pairs in the 1970s to more than 700 pairs today, so has the risk of lead exposure when the hungry birds scavenge winter meals from the leftover parts of deer, bear, moose and other game left by the thousands of hunters who use bullets made of the grey, malleable metal.

Even when a lead bullet is covered in a layer of copper, known as jacketing, tiny lead particles still diffuse through an animal’s soft tissue when the bullet strikes its target and begins to break apart. Research shows that as much as one-third of the bullet’s weight splinters into these tiny particles, which are often invisible to the unaided eye but show up as a sprinkling of bright, white dots when a carcass or a cut of game meat is X-rayed.

Particles will even be left behind when a bullet passes cleanly through an animal. The distribution of the particles is consistent, regardless of the placement of the shot. Research has shown that within an animal’s body, the particles can travel up 18 inches from the path of the projectile, Call said.

Lawmakers and national officials have considered banning lead use in ammunition. A phased-in ban on the use of lead-based bird shot to hunt ducks and other waterfowl began in the 1987-1988 hunting season, went national in 1991, and still stands today. On the last day of the Obama administration, the outgoing director of the U.S. Fish and Wildlife Service expanded a ban on lead use on federal lands to include all ammunition and fishing tackle, but that was reversed by Trump appointee Ryan Zinke in 2017.

Maine bans the use of some types of lead fishing gear, but there are exceptions. There is currently no state-level ban on using lead ammunition to hunt.

More than 50 eagles test positive over 5 years

In the last five calendar years, doctors and staff at the Avian Haven bird hospital in Freedom have found 57 eagles that tested positive for elevated levels of lead, said Diane Winn, Avian Haven‘s executive director, who co-founded the nonprofit wildlife clinic in 1999.

“It’s important to note that among wild animals, raptors are at the top of the susceptibility (scale),” said Winn. “If a person and an eagle consume the same amount of lead, the eagle is much more likely to die. But the person might not have any signs at all.”

On Wednesday, staff at the animal clinic euthanized the last of the five sick birds that arrived between Jan. 1 and Jan. 12 from North Pond, Thorndike, Sullivan, Chester and Peru. Game wardens found that the injured eagle discovered in Peru had been shot, and it was euthanized because of the shooting injury. But it, too, had elevated lead levels.

The arrival of each sick eagle at the hospital was announced in a post on the group’s Facebook page, where concerned bird-lovers have left notes of thanks and commiseration.

The problem of lead poisoning has been documented nationwide in eagles since the 1990s, Winn said, and affects other raptors as well. In California, a 2012 study by a conservation group attached to the San Diego Zoo found that two-thirds of the 135 deaths of endangered California condors recorded between 1992 and 2009 were attributed to lead poisoning. Avian Haven has been testing for lead since the early 2000s, and the state has kept track of those results since 2004.

In response to the effects on wildlife, California has instituted a statewide ban on hunting with lead ammunition beginning last July.

But unlike condors – a sinister-looking scavenger with a 10-foot wing span that is federally listed as critically endangered – bald eagles and golden eagles enjoy extra legal protection via a federal law passed in 1940 that makes it a crime to molest, hurt, kill or possess any eagle part, including its feathers, without special dispensation.

Since 1970, federal conservation authorities have also mandated the collection of every bald or golden eagle carcass found, and they are shipped to the National Eagle Repository in Colorado. There, the eagle parts are broken down and re-distributed to members of native American tribes who use them for religious and cultural purposes.

Because of those restrictions, post-mortem study of eagles on a large scale is often difficult – only a small number of facilities have permission to perform eagle necropsies, Winn said.

One of the few authorized veterinary groups is the Raptor Center at the University of Minnesota’s college of veterinary medicine. Researchers there say 90 percent of the roughly 120 to 130 bald eagles the center receives each year have elevated lead levels in their blood. About a quarter of the lead-affected birds have high enough levels to cause clinical lead poisoning, and most of these are euthanized.

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