Nearly half of US bald eagles suffer lead poisoning

“This is the first time for any wildlife species that we’ve been able to evaluate lead exposure and population level consequences at a continental scale,” said study co-author Todd Katzner, a wildlife biologist at U.S. Geological Survey in Boise, Idaho. “It’s sort of stunning that nearly 50% of them are getting repeatedly exposed to lead.”

Lead is a neurotoxin that even in low doses impairs an eagle’s balance and stamina, reducing its ability to fly, hunt and reproduce. In high doses, lead causes seizures, breathing difficulty and death.

The study estimated that lead exposure reduced the annual population growth of bald eagles by 4% and golden eagles by 1%.

Bald eagles are one of America’s most celebrated conservation success stories, and the birds were removed from the U.S. Endangered Species List in 2007.

But scientists say that high lead levels are still a concern. Besides suppressing eagle population growth, lead exposure reduces their resilience in facing future challenges, such as climate change or infectious diseases.

“When we talk about recovery, it’s not really the end of the story — there are still threats to bald eagles,” said Krysten Schuler, a wildlife disease ecologist at Cornell University’s College of Veterinary Medicine, who was not involved in the study.