BRIGHTON, Colo. (KDVR) — A study released this week uncovered a worrying trend for two of Colorado’s most vulnerable bird populations.

That study, which was released on Thursday, took eight years to complete and found that nearly 50% of all bald and golden eagles in the country are suffering from lead poisoning. 

“Their population growth rates are being suppressed by this particular poison, by lead poisoning,” said Vince Slabe, a research wildlife biologist with Conservation Science Global, which was one of several groups that worked on the study.

The results of the study revealed that lead poisoning has been reducing the bald eagle population growth by 4% and the golden eagle population growth by 1%. Members of both species are frequent visitors of the Rocky Mountain state and have been seen at Barr Lake Park near Brighton.

“It’s been wonderful that the population has increased, but now to know that there’s this risk and threat, it’s sad,” said Debbie Stewart. 

Stewart and Trick Runions visit the park regularly to catch a glimpse of the iconic animal. 

“The opportunity to see one is spectacular,” Stewart said.

But researchers fear the resurgence of the eagle could be impacted by continued lead poisoning. 

They believe the issue stems from eagles scavenging on deer and other animals that have been killed with lead bullets.

“Hunters are the solution to this problem of lead poisoning in eagles,” Slabe said.

Another author of the study, biologist Todd Katzmer, said the 1% deficit may seem inconsequential in the grand scheme of things, but for golden eagle growth, it is a significant loss. 

“We’re looking at 1% per year, and you multiple that out by 20 years or 30 years, then you’re talking about thousands of individuals that are being removed from the population,” he says. “It could mean the difference between a stable population, and a declining population.”