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Lead ammunition is a silent threat to bald eagle recovery

A groundbreaking study published in the journal Wildlife Society Bulletin has revealed that the recovery of bald eagle populations is being significantly impeded by exposure to lead ammunition fragments. These toxic remnants, found in wild game gut piles and carcass parts left behind by hunters, are poisoning bald eagles and increasing their vulnerability to additional threats.

Krysten L. Schuler is an assistant research professor at Cornell University and the principal investigator of the study, which received funding from the Morris Animal Foundation. 

“Bald eagles are an iconic American species,” stated Professor Schuler. “Despite the apparent population rebound through major conservation efforts, our work showed that environmental lead sickens and kills bald eagles to such a degree that it makes the populations vulnerable to other threats such as avian influenza or wind energy development.”

Reduced resilience among bald eagles

What sets this study apart from previous research is its innovative methodology developed by mathematician Brenda Hanley, an expert in population demographics.

Hanley’s approach utilized data from seven northeastern states to construct a comprehensive picture of the impact of lead poisoning on bald eagles. The findings confirmed that while lead poisoning has not halted the recovery of eagle populations entirely, it has substantially reduced their resilience to other adversities.

The generous support from the Morris Animal Foundation played a pivotal role in the execution of the study. This support allowed the research team to bring Hanley onboard and create the new modeling tool that was essential for tackling these intricate issues, particularly with limited data. 

Stunted population growth

Kevin Hynes, a wildlife biologist for the New York Division of Fish and Wildlife and a researcher involved in the study, pointed out that lead poisoning has long been identified as a prevalent cause of eagle fatalities, accounting for over ten percent of bald eagle deaths. 

However, the new modeling approach introduced by Hanley enabled the researchers to recognize that lead poisoning is not just a cause of death, but is also stunting the continued growth of eagle populations.

“This is an environmental problem with a currently available and low-tech solution: A simple switch to non-lead ammunition for hunting will eliminate lead ammunition fragments in gut piles and carcass parts, making them unavailable to eagles and other scavengers,” Hynes suggested.

By exposing the pernicious effect of lead ammunition on the survival and resilience of the bald eagle populations, this study highlights the need for a re-evaluation of hunting practices. It ultimately proposes a shift toward non-lead ammunition as an easy yet effective measure to safeguard bald eagles against the deadly threat of lead poisoning.

More about lead ammunition and wildlife

The use of lead ammunition in hunting and its subsequent impact on wildlife has been an area of growing concern among scientists and conservationists. Lead is a toxic heavy metal that, once introduced into the environment, can have deleterious effects on both terrestrial and aquatic ecosystems.

When hunters use lead ammunition to hunt game, it often results in lead fragments remaining in the leftover gut piles or discarded carcass parts. Scavengers, including predatory and carrion-eating birds such as bald eagles, vultures, and condors, can ingest these lead fragments while feeding on these remains. This can cause lead poisoning, a serious condition associated with numerous health problems and even death in affected animals.

Lead poisoning

Lead poisoning in wildlife typically leads to severe physiological complications, including neurological damage, reproductive failure, and weakened immune systems. It’s not just birds that are affected; mammals, too, can experience these effects when they ingest lead particles present in their environment or their prey.

Research has shown that lead poisoning has contributed significantly to the mortality rates of various bird species. For example, a study published in the journal “Wildlife Society Bulletin” found that lead poisoning from ammunition fragments was not only causing sickness and death among bald eagles, but it was also reducing their ability to withstand other threats, impeding the continued growth of their populations.

Widespread ecological impacts

Furthermore, lead ammunition fragments in the environment can dissolve slowly over time in soil and water. This process releases lead into the environment, where it can enter the food chain and potentially affect a wide range of organisms, thus causing a more widespread ecological impact.

Recognizing these threats, some areas have implemented restrictions or bans on the use of lead ammunition for hunting. The alternatives to lead ammunition, such as copper or steel bullets, are just as effective for hunting, and significantly less harmful to the environment and non-target wildlife.

A shift toward non-lead ammunition is not only a viable but a necessary solution to prevent ongoing wildlife loss due to lead poisoning and to ensure healthier ecosystems. This issue highlights the interconnections in nature and emphasizes that the actions taken in one area (like hunting practices) can have wide-reaching impacts on wildlife and the overall health of our environment.


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