Golden eagles (Aquila chrysaetos) in Yellowstone have been equipped with little bird-sized backpacks containing GPS devices designed to monitor their movement and behavior. Tragically, within just a few months of the experiment starting, the very first of these raptors to be tagged was found dead. The cause: lead poisoning.

Hunting is strictly prohibited within the confines of Yellowstone National Park but big game, upland birds, and waterfowl can be hunted in areas on land close to the park's boundaries. Of course, birds are oblivious to park lines and transmitter data show the 5-year-old eagle up to 64 kilometers (40 miles) north of the park. She died shortly after returning to her territory and biologists were able to recover her body close to Phantom Lake on the Blacktail Plateau last December. 

Autopsies of the body and liver revealed the cause of death was lead poisoning, with lead levels way above the lethal limit. The abnormally high concentration of lead suggests the bird had ingested lead fragments while eating carrion.

"Avian scavengers globally are exposed to lead and suffer from lead poisoning," Todd Katzner, a research wildlife biologist at the United States Geological Survey (USGS), told Atlas Obscura. 

"Data show that lead levels in birds usually peak during winter – concurrent with timing of hunting seasons."

As Katzner's statement suggests, lead poisoning is a big problem in the avian world. According to National Parks Traveler, lead shots are the biggest killer of condors. While this latest death marks the third golden eagle trapped for study to have died in the northern Yellowstone region as a result of lead poisoning in the last eight years, The Guardian reports.

Part of the problem is that fragmented bullets often remain in the leftover carcasses of wild game. Scavengers feasting on the remains – like golden eagles and other birds of prey – are then put at risk. They eat the carcass and lead then enters the food chain. 

But there are things we as people can do. The most obvious is to not hunt. Another, public affairs manager for the National Shooting Sports Foundation, Mark Oliva, told The Guardian, is to bury your gut piles. And a third is to use copper bullets and other non-lead alternatives – something conservationists have been calling for for a while. It's less toxic but also more expensive.

Indeed, the Obama administration banned lead shot and fishing tackle in early 2017. However, the legislation was overturned when the then-incoming Secretary of the Interior, Ryan Zinke, took office. His reasoning:  it "was issued without significant communication, consultation or coordination with affected stakeholders."

As for the death of the unnamed golden eagle, it is a stark reminder that birds both outside of and within US national parks risk exposure to lead and other toxins.