Various advocacy groups are asking hunters to stop using lead bullets.
Yellowstone National Park recently fitted a golden eagle with a tracking device for the first time, but it died in December. This week, officials released the cause of death: lead poisoning.
Wildlife biologists equip the birds with GPS units that fit similar to a backpack, and then monitor their movements throughout the year. This particular female had actually flown outside Yellowstone into popular hunting areas.
Officials believe it suffered from lead poisoning after consuming bullet fragments lodged in the scraps of a hunter-killed elk or deer.
"It's a little gut-wrenching because it's so darn hard to trap and tag an eagle, and it's frustrating for the graduate student who's leading the project," Todd Katzner, an eagle scientist with the U.S. Geological Survey in Boise, Idaho, told the Denver Post.
Golden eagles have wingspans that often exceed 7 feet, making them one of the continent's largest birds.
The Yellowstone research project won't end, though, as researchers were able to fit several other golden eagles with tracking devices.
While golden eagle numbers are relatively steady in the United States, they should be higher than they are, which research blames largely on collisions with wind turbines and motor vehicles.
However, perhaps it should be up to hunters—as stewards of the land—to take the lead on this one.
Bryan Bedrosian, a devoted and the research director of the Teton Raptor Center, told the Denver Post he offered opportunities for hunters to exchange lead bullets for copper ones. However, he doesn't believe banning lead bullets is the answer.
"A lot of it's a matter of awareness and willingness of people to switch," he said.
As of July 1, California will prohibit hunting with lead bullets.
Enjoy the outdoors?
Sign up for daily stories delivered straight to your inbox.