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Bald eagles have come a long way in the past several decades. In fact, their population has more than quadrupled in the lower 48 since 2009. However, a new study finds that there’s a lingering threat that continues to hamper their recovery: lead ammunition.Researchers from Cornell University theorized that lead poisoning was impacting species recovery in the Northeast, and they set out to see if that was true. Their findings, published in the Journal of Wildlife Management, seemed to confirm their suspicions. The data showed that though the species’ numbers continue to climb, lead poisoning is decreasing eagle population growth by 4%-6% annually in the region.
Eagles encounter lead when they consume an animal carcass contaminated with it. The researchers explain that switching to a different kind of ammunition, like those made with copper, can help address this problem.
Dr. Krysten Schuler, senior author and assistant research professor in the ­­Department of Public and Ecosystem Health, says, “Hopefully, this report will add information that compels hunters, as conservationists, to think about their ammunition choices.”
To compile their report, the team used a population model and necropsy records to see how a reduced amount of lead in the environment would have impacted the species’ numbers. The records consisted of 1,200 birds that had died between 1990 and 2018 in seven northeastern states. Of those animals, nearly 500 had been tested for lead, and researchers looked to see if their exposure was at a toxic level.
With these methods, the team determined that deaths stemming from lead poisoning had reduced the annual population growth by 4.2% for females and 6.3% for males in the Northeast. They hope these numbers can inspire changes in education and in federal regulations.
The authors write, “The reduction of eagle mortality from (lead) toxicosis can alleviate survival pressure of female hatchlings and breeders, and may return the eagle populations to dynamics that contain robust resilience. The results of this study can be used in efforts by state and federal wildlife managers or non-governmental organizations to educate hunters of the consequences of their ammunition choices or to inform policy surrounding the use of lead ammunition.”
The team says though this study focused on bald eagles, lead poisoning may also be impacting other animals that eat carcasses.
Dr. Schuler told NPR, “What we’ve got is a lot of data on bald eagles. They’re sort of the poster species that we’re using for this issue because we don’t have the same amount of data to do this type of analysis on other species.”
If you’d like to help, you can sign this petition urging federal officials to protect wildlife from lead.