Study suggests nearly half of U.S. bald eagles have chronic lead poisoning; population growth estimated stunted by 4%

A lead-poisoned bald eagle is treated at The Raptor Center
at the University of Minnesota (Associated Press photo)

Nearly half of the bald and golden eagles tested in the United States show signs of chronic lead poisoning, according to a study published this week in the journal Science.

"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," Christina Larson reports for The Associated Press. "Harmful levels of toxic lead were found in the bones of 46% of bald eagles sampled in 38 states from California to Florida. Similar rates of lead exposure were found in golden eagles, which scientists say means the raptors likely consumed carrion or prey contaminated by lead from ammunition or fishing tackle."

Eagles are very sensitive to lead. Modeling suggests that such high lead-poisoning levels have reduced annual population growth of bald eagles by 4% and golden eagles by 1%, Larson reports.

“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,” study co-author Todd Katzner, a U.S. Geological Survey wildlife biologist, told AP, which notes, "Lead ammunition for waterfowl hunting was banned in 1991, due to concerns about contamination of waterways, and wildlife authorities encouraged the use of nontoxic steel shot. However, lead ammunition is still common for upland bird hunting."