Bald Eagle Population Recovery Hampered by Hunters’ Left-Behind Lead Bullets

by Samantha Whidden
(Photo by Jesse Wild/Digital Camera magazine via Getty Images)

The U.S. bald eagle population recovery is reportedly being hampered due to hunters leaving behind lead bullets in their natural habitats.

Reuters reports that the bald eagle is no longer on the brink of extinction in the U.S. But the population now has to deal with an increasing number of lead poisoning deaths. This is due to the birds ingesting hunters’ lead bullets.

A study done by researchers at the Department of Public and Ecosystem Health at Cornell University reveals that the population increases of the bald eagle are being suppressed by 6.3% for males and 4.2 for females. The study states, “Mortalities from the ingestion of [lead] reduced the long-term growth rate and resilience of bald eagles in the northeast United States over the last three decades.”

Some hunters who field dress are leaving behind organs that contain lead ammunition. The eagles then eat the remains and ingest the lead.

The bald eagle is now off the national endanger and extinct species list.  However, the study from Cornell explains, “While abundances have increased, ingested [lead] has a negative effect on the [bald] eagle populations in the northeast United States. These conditions have stressed the resilience of this population.”

How Lead Poisoning Has Caused Harm to the U.S. Bald Eagle Population

Cornell’s recent studies have reported that there were 2,050 breeding bald eagle females in 2018. This was a reduction of an estimated 98 breeding females as a result of lead poisoning. Also that year, there were more than 10,000 females who were not reproducing. With a reduction of an estimated 742 non-breeding females as a result of lead poisoning.

Meanwhile, in 2018, there were 2,050 breeding males; and a maximal reduction of an estimated 65 breeding males due to lead poisoning. There were 10,172 non-breeding male eagles; and a maximum reduction of an estimated 1,645 non-breeding males as a result of the poisoning. 

Speaking about the findings, researchers declare, “This study can be used by state and federal wildlife managers. To inform policy surrounding the use of lead ammunition. Or to educate hunters on the population-scale effects of their ammunition choices.”

What Other Species are Seeing Negative Impacts of Lead Poisoning 

According to the National Park Service, other wildlife affected by lead poisoning include the California Condor. Over the past three decades, the California Condor recovery reveals just how lead can be threatening to the survival of a species. 

Semi-annual test results have shown that the majority of free-flying condors at the Pinnacles National Park have blood lead levels that exceed 10 ug/dl. Which is the same threshold by the CDC as an initial warning sign that a human child is at risk. “Some condors have been measured with blood lead levels higher than 800 ug/dL. A value that would potentially kill a human.”