Nearly Half of U.S. Bald and Golden Eagles Show Signs of Repeated Lead Exposure

Original Article: https://blog.theanimalrescuesite.greatergood.com/eagles-lead-exposure/

Bald eagles have been a conservation success story, with a population more than quadrupling over the past ten years. However, lead poisoning continues to be an issue for the iconic birds, with one study showing their recovery in the Northeast would be even higher if not for lead. Now, a new multi-agency study shows the problem is even more widespread.

Scientists from the U.S. Geological Survey, the U.S. Fish and Wildlife Service, and Conservation Science Global, Inc. examined the amount of lead exposure in bald and golden eagles between 2010 and 2018. Their findings, published in the journal Science, indicate that nearly half of these birds may experience repeated lead exposure.

eagleslead5 - Nearly Half of U.S. Bald and Golden Eagles Show Signs of Repeated Lead Exposure — PHOTO: PIXABAY / ROBBROWN2020

Todd Katzner, lead USGS author and USGS wildlife biologist, says, “This is the first study of lead poisoning of wildlife at a nationwide scale, and it demonstrates the unseen challenges facing these birds of prey. We now know more about how lead in our environment is negatively impacting North America’s eagles.”

To estimate how prevalent the problem is among both species, the team took samples from more than 1,200 eagles across 38 states, including Alaska. They found that 46% of the bald eagle samples and 47% of the golden eagle samples showed signs of chronic lead exposure. Based on demographic modeling, the team says this level of exposure suppresses population growth of bald eagles by 3.8% each year and of golden eagles by 0.8% annually.

eagleslead4 - Nearly Half of U.S. Bald and Golden Eagles Show Signs of Repeated Lead Exposure — PHOTO: PIXABAY / CHRISTIANGEORG

Eagles generally come across lead when they eat dead animals that were killed with lead ammunition. The authors note that this is more apt to occur in the winter time when it’s harder to find live prey. They found that the older an eagle was, the higher their amount of lead exposure. Over time, lead accumulates in their bones. If the exposure is high enough, it can render eagles unable to fly, digest their food, or even move properly.

The authors note that this issue is especially problematic for one species.

Brian Millsap, study co-author and U.S. Fish and Wildlife Service National Raptor Coordinator, explains, “The study’s modeling shows that lead reduces the rate of population growth for both of these protected species. That is not as impactful for bald eagles since this endemic species population is growing at 10% per year across the U.S. In contrast, the golden eagle’s population is not as stable, and any additional mortality could tip it towards a decline.”