How were these eagles poisoned?
The first sick eagle that Avian Haven received this year was found on New Year’s Day in central Maine, laying on the ice of North Pond.
The next day, another sick eagle was transported to the wildlife rehabilitation center. It had been wandering around Thorndike, struggling to fly.
A few days later, an eagle was found lying on the ice of Flanders Pond in Sullivan. Not long after that, an eagle was spotted on the ground in North Chester, and another was rescued from a frozen riverbank in Peru.
How did this happen?
Lead poisoning occurs when animals — including humans — ingest lead. The metal then travels through the bloodstream and starts damaging organs.
This lead can come from a variety of places. For people, a big concern is
lead-based paint. For loons, X-rays show that the culprit is fishing tackle. And for eagles, it’s fragments of lead ammunition that the bird has consumed by eating contaminated meat.
“Although lead fishing tackle is an issue for loons, it’s well documented that spent lead ammunition in large game such as deer, left on the landscape, is the primary source of lead poisoning for eagles,” said Erynn Call, raptor biologist for the Maine Department of Inland Fisheries and Wildlife.
When Avian Haven receives a sick eagle, the staff performs an X-ray. In some cases, they have found fragments of lead ammunition in the bird’s digestive tract. But often, they find nothing at all. That’s because eagles cough up pellets of indigestible materials.
In the absence of physical evidence, another thing supports the idea that eagles get sick from ammunition, not fishing tackle, is timing.
“We almost never see cases of lead poisoning [in eagles] in the summer when their prefered diet is fish,” Winn said. “But in the winter months, basically October through April, that’s when we see eagles coming in with lead poisoning.”
During the winter, when Maine’s lakes and ponds are frozen over, eagles transition from eating fish to eating other types of meat, including roadkill, bait piles and discarded deer carcasses from the previous hunting season. These animals are primarily hunted with lead ammunition.
“When an animal is shot with a lead bullet, as much as a third or more the bullet’s total weight will be fragmented into hundreds of tiny pieces upon impact and remain inside the animal,” Call said.
Some of these lead fragments are so small they aren’t visible to the naked eye.
“If internal organs or gut piles of a carcass are left in the field or used as bait, scavengers such as bald eagles will be attracted to that,” Call said. “A lead fragment the size of a grain of rice can kill an eagle.”
What can be done?
In response to the number of loons dying from lead poisoning, Maine passed
a series of laws from 2002 to 2016 that banned the use of certain types of lead fishing tackle. In addition, lead ammunition has been banned by the federal government in the hunting of waterfowl since 1991.
But no such law exists in Maine for hunting game such as deer, moose, bear and upland birds.
Whether hunters use lead ammunition or non-lead ammunition (made of copper) to hunt those animals is a choice, one that could make all the difference.
“Overall, the bald eagle population is healthy and continues to grow and expand [in Maine],” Call said. “However, the Maine DIF&W is concerned and recognizes that cases of bald eagle exposure due to spent lead is an issue.”
In response, the Maine DIF&W recently joined a partnership with other Northeast fish and wildlife agencies to initiate an education and outreach program to promote the benefits of using
“I think it’s important to note the history of hunting and fishing and how critical it has been over the history of our country for conserving wildlife,” Call said. “The choice of using lead-free ammunition provides hunters with another opportunity to be wildlife conservationists.”
Winn has seen firsthand what a difference outreach and education can have on people’s decisions.
“I’ve had so many conversations with friends who are hunters who would say, ‘I just had no idea and I’m switching over to copper as of now,’” Winn said. “I think any hunter who truly understands what’s happening will want to make the change.”
Can poisoned eagles be saved?
In eagles, lead poisoning often impacts the brain, nervous system, heart and gastrointestinal tract. As the sickness progresses, the bird becomes disoriented and weak. They struggle to hunt, fly or even stand.
“Birds are uniquely vulnerable to lead contamination because of their adaptation for digestion,” Call said. “And eagles, because of the highly acidic nature of their stomach, are more vulnerable.”
The severity of the damage depends on a number of factors, including how much lead they’ve consumed, how long it remained in their digestive system and whether the bird had any prior exposure to lead or other chemicals, Call said.
To complicate matters further, lead poisoning can be indirectly responsible for an eagle’s death.
“Let’s say you have an eagle with moderate lead exposure feeding on roadkill and a car comes and they’re too clumsy or uncoordinated to get out of the way because the lead has impaired them,” Winn said.
The Raptor Center in Minnesota show this correlation between injured eagles and lead. Of the 100-plus eagles they recieve for treatment each year for all types of problems, 90 percent have elevated lead residues in their blood. Furthermore, between 20 and 25 percent of those eagles have high enough blood lead levels to be diagnosed with “clinical lead poisoning.” Most of those birds die or are euthanized.
“The successes with those birds are very few and far between,” Winn said.
Credit: Courtesy of Avian Haven
Still, Avian Haven and other wildlife rehabilitation centers try their best to help every eagle they recieve.
“We treat the eagle the same way a person would be treated, with what’s called a chelating agent, a drug that will bind to the lead ions in the bird’s body and render them less harmful,” Winn explained.
The eagle also receives supportive care, nourishment and a quiet, warm place to rest. Every once in a while, the bird will pull through if the damage caused by the lead isn’t too severe.
This past October, a male juvenile bald eagle was found in the water of Norway Lake. The young bird made it to shore by the time the responding game warden, Tim Coombs, arrived, but it was too weak to resist capture. Upon being tested at Avian Haven, the eagle was found to have a moderately high blood lead level and was immediately treated.
“Chelation was successful,” Winn said. “But more importantly, he had no injuries or discernable after effects.”
The eagle made a full recovery and in December, was released back into the wild. The Avian Haven staff can only hope he doesn’t find another source of lead on the landscape. Next time, like the five other eagles found this month, he might not be so lucky.