Bald eagle population growth slowed by lead poisoning, study finds

Bald eagle population size is affected by lead poisoning, according to scientists from Cornell University’s Department of Public Health and Ecosystems. One study found that the birds ate hunters’ hunting ammunition, reducing their population growth by 4-6%.

For the study, published in the Journal of Wildlife Management, scientists have looked at population growth figures to bald eagle population across the northeast. They found that hunters who “field dress” their prey and leave contaminated organs in place endanger the eagles that scavenge the remains. Other species including owls, crows, coyotes, foxes, anglers and bears also eat the remains, meaning they are all at risk of poisoning.

“We didn’t collect data on these other species in the same way that we pay attention to eagles,” said Krysten Schuler, assistant research professor in Cornell University’s Department of Public Health and Ecosystems and lead author. of the study. “We present eagles as a kind of poster for this problem, but they are not the only ones affected.”

Even humans can be affected if they eat game species that contain lead fragments.

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The research team hoped the information would inform hunters – and political policy – ​​about ammunition choices, such as copper-based ammunition.

Reduced growth rates of bald eagles have the ability to undo a “cushion” for the population, which would protect them against unforeseen events like natural disasters or the West Nile virus that could decimate the population, the researchers said. researchers.

The eagle population, which was once threatened by the use of DDT during World War II, had started to rebound after the enactment of the 1973 Endangered Species Act. In fact, their population size in the lower 48 quadrupled between 2009 and 2021.

However, scientists estimated that bald eagle growth rates were suppressed by 4.2% for females and 6.3% for males.

“Even though the population appears to have recovered, disturbances could occur that could cause the eagles to decline further,” Schuler said.