A new study in Science has a stat that doesn't bode well for bald eagles—and is even worse for golden eagles: "Almost half of all animals sampled had chronic, toxic levels of lead." Researchers tested more than 1,200 live and dead eagles from across the US between 2010 and 2018, reports the Wall Street Journal. They found that 46% of bald eagles had chronic lead poisoning and 47% of golden eagles had the same, per NBC News. The main culprit? Lead bullets. As in, the birds scavenge on animals shot by hunters, and the lead from the ammunition contaminates them as they feed.
“This is the first time for any wildlife species that we’ve been able to evaluate lead exposure and population level consequences at a continental scale,” study co-author Todd Katzner, a wildlife biologist at US Geological Survey, tells the AP. “It’s sort of stunning that nearly 50% of them are getting repeatedly exposed to lead.” His team estimates that lead poisoning suppresses the population growth of bald eagles by about 4% a year and golden eagles by 1%. However, that lower figure might actually be more devastating to golden eagles because fewer of them exist.
While the number of bald eagles in the US is thought to be more than 300,000, the number of golden eagles is roughly one-tenth of that. “Little impacts can add up over time,” Katzner tells NBC. “In 20 years, that adds up to thousands and thousands of golden eagles removed from the population.” One of the contributing factors to the problem is that bullets can fragment when they strike, say, a deer. And "a lead fragment the size of a grain of rice is enough to kill an eagle,” Cornell's Krysten Schuler tells the Journal. "This is an anthropogenic source of mortality for eagles.” (Read more bald eagle stories.)