Indiana's soaring bald eagle population not only delights bird watchers and raptor lovers, it’s a good sign for the state’s ecosystems.
“Any time you see the top of the food chain doing well, it means everything under it is stabilizing,” said Pat Funnell, a veterinarian for Soarin' Hawk Raptor Rehabilitation Center, which rescues injured birds of prey near Fort Wayne.
But threats such as lead poisoning continue to shadow the national bird's population in the Hoosier state, which has increased steadily since the pesticide DDT was banned in 1972.
When eagles eat fish contaminated with DDT, their eggs have weak shells and rarely produce healthy chicks.
Re-population efforts began in Indiana in 1985, when the Indiana Department of Natural Resources began releasing 73 bald eaglets, brought in from Wisconsin and Alaska, 10 at a time into the Lake Monroe area near Bloomington.
The population grew in the ensuing decades and continues to expand. According to a DNR report from 2016, bald eagle nesting has been confirmed in 83 of the state's 92 counties with an estimated 300 breeding pairs statewide. Sixty-five new nests were discovered in 2016 alone.
Long-term data show an increase of roughly 6 percent in winter nesting pairs year-over-year, with most new nests found in the state’s southwest corner.
Indiana’s program is so successful that some young eagles have to leave the state to stake out their own nesting territory. The DNR has tracked Hoosier bald eagles as far as New York, though some returned to Indiana to have chicks, according to the 2016 report.
Re-population efforts, coupled with the bald eagle's inclusion for a time on the state's endangered species list, helped to bring the species back from the brink, according to Funnel.
But Kathy Hershey, founder and president of Utopia Wildlife Rehabilitators based in Hope is beginning to see the birds’ increasing population work against the species.
Competing for territory
As eagles spread across the state, they compete for food and territory. Hershey is seeing more eagles brought in for treatment of injuries suffered in fights.
“They like water, they like waterways," she noted. "If they are always competing for territory, on one hand, it’s good, because they are growing. But we will always have to watch them.”
Most eagles stake their claim to about a mile of territory and nest in a large tree, such as a sycamore, near a large lake or stream.
Fish is a main part of their diet. Eagles also scavenge meat from road kill and hunt small mammals such as field mice or rabbits and even small birds or ducks.
As bald eagles become more numerous, competition forces them to feed on more carrion, Hershey said. That, coupled with relaxed regulations, brings another danger for the national bird: lead poisoning.
Heavy metals
Hershey said symptoms of lead poisoning have become more common in animals treated at Utopia Wildlife.
“All you have to do is watch one of these animals,” she said. "They can’t coordinate, they can’t eat, and your probability of bringing them out of it -- well, most of them can’t be saved."
Hershey and Funnell blame hunters and fishermen who use lead shot or lead sinkers and leave them in the eagles' habitat.
When hunters clean a kill, they often leave the shot-riddled entrails in the woods. If an eagle eats the entrails, it also consumes the lead.
“Just a tiny, small lead pellet can kill an eagle,” Funnell said.
She noted that the majority of hunters are willing to pay extra for steel or copper bullets: “Most hunters consider themselves conservationists and care about wildlife.”
But some simply aren’t aware of the environmental problems associated with lead -- or they ignore the peril to wildlife.
Several states have banned lead shot and fishing tackle, and President Obama outlawed the materials in federal land, as well, in his last days in office. New Secretary of the Interior Ryan Zinke rolled back the ban in March.
Gun-rights and sportsmen groups contend that the ban would have forced them to buy more expensive steel or copper bullets. Lead-free bullets can cost from 50 to 100 percent more than soft-point lead bullets, according to leadfreehunting.com.
A study conducted by the Center for Biological Diversity estimates that more than 20 million wild animals die each year from lead poisoning. Additional studies show lead can end up in game meat even after processing, harming human consumers.
Soarin' Hawk was taking in so many birds with symptoms of lead poisoning that the rescue purchased a lead-testing machine to avoid the five-day wait for results from samples sent to a lab.
Overall, Hershey said, Indiana's eagle population is highly vulnerable.
Just as eagles' place atop the food chain casts them as a barometer for the health of the natural world around them, so too are they sensitive to even small changes in their food supply and environment.
For now, Hershey is cautiously optimistic.
“They are beautiful, and we love having them back,” she said of Indiana's bald eagles. “And it’s up to us to do what will help.”