Experts say that environmental lead debris continues pose a significant threat for the bald eagle population in the United States, and New Mexico.
A U.S. A U.S. Fish and Wildlife Service report published in 2020 estimated that there were roughly 316,000.00 bald eagles within the lower 48 states. This figure is a revival after the 1960s, when the country’s eagle population was nearly extinct. Science published in February revealed that nearly half the bald eagles have been poisoned with lead. They often eat dead carcasses of animals that have been killed by hunters.
There are many different ways they can get there. [poisoned]. Sometimes it comes from hunter-harvested animals who have been shot with lead bullets. Sometimes it’s passively being absorbed by the environment from pollution. Sarah Sirica is a doctor in veterinary medicine and staff veterinarian at New Mexico Wildlife Center Espaola.
Sirica stated that although there are a few bald eagles living in New Mexico, they are mostly migratory. According to New Mexico Avian Conservation Partners (NMAP), bald eagles breed mainly in Alaska and Canada. According to the New Mexico Avian Preservation Partners, they are most common in Colfax, Sierra, and Colfax counties. She currently has three golden eagles on-site.
The brains of birds of prey and eagles are most affected by lead exposure. Sirica stated that poisoned birds can become less vocalized and may lose their ability to stand, depending on how much lead poisoning they have received. They may also experience problems with digestion. Sometimes, the digestive tract can become dysfunctional.
Dennis Miller, a retired professor emeritus in biology at Western New Mexico University, is the director of Gila Wildlife Rescue, based in Silver City. Miller has only seen two bald eagles in his time at the rescue. He stated that the last one he had to treat was the result of four eagles having eaten fish with lead inside them. He said that two of them died, one vanished and the other was brought to his rescue.
He has found that nearly all birds are poisoned by lead pellets.
It’s the lead-pellet being digested and absorbed by their very strong digestive enzymes.
Sirica explained that if there is suspicion of lead poisoning, the center will take a small sample from the bird’s blood. She said that an in-house blood test is done using a specific analyzer which will determine the blood lead concentration. They will administer medication that binds to the lead particles and allow them be excreted from the bird’s droppings. They will also remove any lead particles from the bird’s digestive tract.
She explained that the medication can be very hard on their internal organs, and that they often need fluid support. It can take several weeks for them to fully recover and be able to be released into the wild. She stated that many birds die from excessive lead exposure.
Robert Murphy, a wildlife biologist at Eagle Environmental Inc. and a former USFWS biologist, said that anticoagulant rodenticides can also be toxic to birds of prey. Murphy stated that they are often used against prairie dog in rural New Mexico and Arizona. They cause internal bleeding, which ultimately leads to them dying.
According to Murphy, lead poisoning is still a major cause of death among golden eagles. When they are exposed, their neurological function is affected and they will likely collide with cars and power poles.
A lead bullet that hits a deer with its bullet fragments tiny bits of lead. This is a great science fact, but it’s hard to believe that all these tiny pieces of lead scatter. It doesn’t take much [for]When scavenging, eagles will only pick up a few pieces. It is enough to cause elevated lead levels in the blood and put them in semi-conscious mode, Murphy said.
Murphy, a hunter himself made the switch to nonlead ammunition some time ago.
Many hunters still use lead, and many aren’t aware that it is a major mortality factor for eagles as well as other bird species, Murphy said.
Sirica said that although she cannot accurately determine the lead poisoning rates of New Mexico and other states, the population dynamics in other places differ. However, she believes that the phenomenon is present.
