A study published in Science in February found that North American eagles are being seriously impacted by lead poisoning. Up to 50 percent of the birds sampled had high levels of lead in their organs, enough to slow population growth by 3.8 percent in Bald eagles and 0.8 percent in Golden eagles. The Bald eagle population is growing by 10 percent per year, and so is not as seriously impacted as are Golden eagles, whose population is less stable and therefore more easily tipped to a decline.

“We now know more about how lead in our environment is negatively impacting North America’s eagles,” says the U.S,. Geological Survey’s Todd Katzner, one of the authors of the study.  The researchers determined that eagles are being poisoned by ingesting lead bullet fragments in carcases and gut piles left behind by hunters, especially in winter, when eagles rely more on scavenging than they do in summer.