Yellowstone National Park officials say a golden eagle died of acute lead poisoning, likely from feeding off gut piles contaminated with lead shot.
The park says the female eagle was the first in park history to be fitted with a radio transmitter. The raptor was part of a long-term study of wildlife in Yellowstone.
The eagle ranged north of the park extensively in the fall of 2018, which is probably where it ate carrion contaminated by lead fragments, the park says. A necropsy of the bird showed lead levels well above lethal toxicity.
"Lead is an environmental toxin well known for its capability to directly impact wildlife," a park release says.
The Obama Administration outlawed the use of lead bullets due to their impact on wildlife. The Department of the Interior under then-Secretary Ryan Zinke repealed the ban in 2017.
Some hunter groups recommend copper or copper-alloy bullets as a safer alternative to lead.
Golden eagles are a species of concern in Yellowstone, meaning that they are not listed as endangered but their population is in decline.