A bald eagle rescued after being caught in fishing line on the Minnesota River had early stages of lead poisoning, possibly after ingesting bullet fragments.
The Raptor Center said the eagle rescued from the Mankato area had been recently exposed to lead, which the University of Minnesota-run center says has been a major health issue for birds admitted over the past 40 years.
In this instance, the lead toxicity was caught early because the bird was brought to the center for another reason, but others are not so lucky.
It raises an "important environmental message" about the use of lead ammunition by hunters, with eagles picking up traces of the toxic metal when picking at a deer carcass or a gut pile.
According to the center, 90 percent of the 120-130 bald eagles admitted each year have elevated lead residues in their blood, and 20-25 percent have sufficiently high levels that causes them to die or be euthanized.
More than 500 eagles admitted to the clinic in the past 24 years have been euthanized due to lead poisoning, with the center's investigations identifying lead ammunition from shotguns and rifles as the main source of the exposure.
Science site Undark reported lead fragments can extend as far as 18 inches from the bullet's path through an animal, and so hunters can sometimes miss them when trimming carcasses.
Minnesota DNR hunter and educator Carrol Henderson told the website evidence of the effects of lead exposure not just on wildlife but human health too "is so overwhelming, in fact, that the lack of more aggressive regulation borders on the absurd, if not downright negligent."
Use of lead bullets polarizes opinion
Attempts to restrict the use of lead bullets in hunting have proved to be a polarizing subject in Minnesota.
Last year, the DNR attempted to ban the use of lead shotgun pellets for hunting game including wild turkey, grouse and pheasant on several wildlife management areas in Minnesota. Lead ammunition has been banned for waterfowl hunting since 1987.
But despite the views of Henderson, the Pioneer Press reported there remains some debate in scientific quarters as to the impact of lead poisoning, with DNR wildlife program manager Steve Merchant admitting last year they "don't have science" that shows it negatively impacts a whole population.
Ryan Burt, president of the Minnesota chapter of Safari Club International, told MPR News bird populations, including eagles and other species once endangered, are thriving despite the use of lead shot by hunters.
Nonetheless, the DNR argues lead still remains a toxin that can have acute and chronic health effects, and it makes sense to limit a toxin that would otherwise persist in the environment for decades.
While some small game hunters have switched to non-toxic ammunition anyway, there also remains opposition to a ban amid concerns over protecting Second Amendment liberties.
The Worthington Daily Globe reported former Minnesota Rep. Tom Hackbarth, a Republican, last year put forward a bill to stop the DNR from banning lead ammunition, accusing the department of overreach.
A similar bill has been proposed for this year's legislative session, which states "the commissioner of natural resources shall not adopt rules further restricting the use of lead shot."