Once an endangered species, the population of bald eagles in New York continues to grow. But their success is not without threats to continued population growth. They are unintended threats — but threats nonetheless, according to Cornell researchers.

Krysten Schuler scrolled through photographs of bald eagles in her office at the Cornell University Wildlife Lab in Ithaca. Eagles that died in the wild, which were reported to conservation officers.

“The public is more likely to report bald eagles because of their iconic status,” said Schuler, a wildlife disease ecologist and director of the lab.

The particular eagles in the photos either died of lead poisoning or had elevated levels of lead in their system. Schuler and other researchers have studied the impact of lead poisoning on wildlife.

“Our goal was to identify which animals should we be looking at,” she said. “And bald eagles rose to the top of the list as being the most susceptible to lead poisoning.

Eagles, by nature, are scavengers. Exposure to lead happens when they pick on carcasses of deer and other wildlife shot by hunters using lead bullets. Ammo which, as a ballistic gel shows, fragments significantly after impact.

“Bald eagles seem to be impacted because of their physiology,” said Schuler. “Also, because they're not going to pass up that free meal, they may ingest more than other smaller animals might.”

The bald eagle represents a great conservation success story. Once endangered, populations continue to grow. Schuler says research shows that growth may be happening slower than it could be. In eagle carcasses brought to the lab for study, samples highlight the impact of lead poisoning.

“It didn't stop the recovery,” she said. “But it just kind of slowed the recovery down from what it could have been.”

Schuler says research is important because it highlights that lead is still a health issue for wildlife, especially eagles. Some species are more vulnerable to lead poisoning than others. Eagles specifically have a high acidity in their stomach, so they mobilize lead more quickly, she said.

The New York State Department of Environmental Conservation has an education campaign which Schuler is part of, designed to educate hunters on the potential impact of lead ammo. It encourages other options, including non-lead copper ammunition. Schuler herself is a hunter, and she uses it, adding she sees no difference while hunting. Schuler says if non-lead ammo does not work for a hunter, then they’re encouraged to remove lead-tainted carcasses from the field.

Schuler says Cornell researchers continue to study the potential impact of lead on other wildlife that scavenge deer carcasses. They’re using trail camera photos and footage from the public to help identify those animals. The bald eagle study includes data from birds in seven northeast states, including New York.

All ways that scientists and conservationists say the population of the bald eagle can continue to soar.

“This is not anything to do with anti-hunting or removal of guns,” said Schuler. “This is about educating people about how they can recreate in a way that's not harming species that weren't intended to be taken during their activities.”