Eagles Poisoned at High Rates by Lead Ammunition

A recently published study in the journal Science (Slabe et al., 2022) documented alarmingly high levels of lead in bald and golden eagle populations across the United States. Nearly half of the animals tested from both species had lead concentrations in their bones above the threshold for chronic poisoning, suggesting repeated exposure to the toxin over a long period. Additionally, feather, liver, and blood samples indicated that approximately 35 percent of bald eagles and 7 to 35 percent of golden eagles sampled had experienced at least one acute lead poisoning event, indicating a high level of exposure from a single source.

While levels were elevated in populations across the country, eagles living in the Central Flyway—which spans the Rocky Mountains, Great Plains, Southwest, and western Gulf Coast—had higher rates of lead poisoning than populations located in either the Atlantic or Pacific Flyways. The authors concluded that lead poisoning was suppressing population growth rates by nearly 4 percent for bald eagles and nearly 1 percent for golden eagles. 

Lead bullets used by hunters are the primary source of lead ingested by the eagles. Eagles often scavenge the remains of hunted animals, which frequently contain bullet fragments, and the authors found that use of lead ammunition during hunting season corresponds directly with acute poisoning events. Poisoning from lead bullets has been documented in a wide variety of species, including red-tailed hawks, sandhill cranes, coyotes, black bears, and California condors, an endangered species. Lead exposure is also a concern for humans who consume wild meat, as studies have linked the regular consumption of game meat to elevated levels of lead in the blood, which—particularly in children—can negatively impact health and cognitive functioning in a variety of ways. Cost-effective, nontoxic alternatives to lead bullets are widely available, and AWI is working to encourage adoption of these safer options. 

Program Terms: Terrestrial Wildlife

AWI Quarterly Terms: Quick Read