Glacier National Park officials say an immature bald eagle found at Lower McDonald Creek in February died from lead poisoning, but did appear to have been shot.

Park biologists sent the carcass to the National Wildlife Health Center in Madison, Wisconsin for further evaluation after an initial assessment did not show evidence of gunshot or other obvious signs of trauma.

Bald eagles are protected by the 1940 Bald and Golden Eagle Protection Act, which prohibits poisoning them, among a number of other activities, the Park noted in a release.

This is not the first eagle found in the West Glacier area that died from lead poisoning. In April 2012, park staff found a sub-adult golden eagle carcass in the same vicinity. A necropsy also determined that lead poisoning was the cause of death. A similar case was recently discovered in Yellowstone National Park. There, a radio-tracked golden eagle that was part of a study died from lead poisoning.

The necropsy for the most recent Glacier Park bald eagle found the immature female bald eagle to be emaciated. The eagle’s gall bladder was distended and filled with viscous, green bile, which is typical in birds killed by lead poisoning.

Lead is a naturally occurring heavy metal that has been used by humans for many purposes for thousands of years. It has also been used in the manufacturing of lead fishing sinkers and hunting ammunition. Although both lead fishing tackle and hunting are not permitted in Glacier, eagles do not spend their entire lives within the park boundaries and can be exposed to lead outside of the park.

They typically ingest lead from animals shot by lead bullets, ingesting the fragments. If an eagle ingests enough lead, it can kill the bird.

Eagles will feed on dead rodents left in fields or pastures after being shot, and on guts piles left by hunters in the fall. If the hunter used lead ammunition, small lead bullet fragments are usually present in the carcass. Non-lead ammunition is safer for wildlife, the park notes.

More recently, some hunters have been converting to copper bullets, though they do cost more.

Hunters who choose to use lead ammunition can reduce impacts to wildlife by removing gut piles from the field and disposing of them in plastic garbage bags, the Park recommends.