Bald Eagles, the symbol of the United States, have been recovering and growing in population rapidly over the course of the last decade. According to the U.S. Fish and Wildlife Service, these raptors have more than quadrupled in number since the year 2009. This is welcome news after the pesticide crisis which once interfered with their reproductive abilities and diminished Bald Eagle numbers into the triple digits. A new threat to this recovery has recently been identified, however, and it is estimated to affect up to half of the nation’s Bald Eagle population. This threat? Lead poisoning.
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How Serious is Lead Poisoning For Eagle Populations?
According to the Raptor Center at the University of Minnesota’s College of Veterinary Medicine, up to ninety percent of the sick or injured Bald Eagles that they treat each year present with some amount of lead in their blood. A significant portion of these raptors, reported to be between twenty-one and twenty-five percent, suffer from toxicity due to the presence of lead, with many of these cases being fatal.
Even a miniscule amount of lead in a bird’s system has the potential to cause symptoms that range from moderate to devastating. Lead can cause seizures, neurological dysfunction, digestion issues, and can be fatal even in small amounts.
Where is the Lead Coming From?
The consistent exposure of Bald Eagles to lead may seem mysterious, but evidence points to a major contributing factor that accounts for this phenomenon. Bald Eagles, though their reputation paints them as noble hunters and fishers, are known to be scavengers as well. Conservation organizations, including the U.S. Fish and Wildlife Service, point to lead in bullets as the main culprit for the lead in raptors’ systems.
Lead ammunition, fired by hunters, leaves fragments of lead into the carcasses of the game that they catch. Often, even if the carcass is recovered and the bullet removed from the ecosystem, quantities of lead are left behind when game is gutted and the “gut piles” are left behind. Bald Eagles frequently scavenge leftover scraps, unwanted guts, and discarded carcasses left by hunters.
Because lead bullets can be so damaging to the environment, they are already banned from use in waterfowl hunting. Some U.S. states have even begun to ban the use of lead ammunition in all forms, however nationwide it is still a common material for ammunition. For this reason, the Fish and Wildlife Service recommends that hunters select lead-free and nontoxic options for ammunition when available. Additionally, it is suggested that hunters take care to hide or dispose of “gut piles” and remove all remaining shot, bullets, or fragments from the environment. Carcasses with lead fragments should never be left in the wild for scavengers to find. Lead fishing tackle has also been identified as a potential source of harm, with fishers encouraged to choose tackle made from nontoxic materials.
Although some question the role of ammunition in the widespread exposure of Bald Eagles to lead, the fact that exposure numbers correlate directly with deer hunting season is a pretty damning piece of evidence. Lead remains the most common ammunition material for deer hunting, at the potential cost of the health of this species which has already triumphed over significant challenges.
Conservation agencies do not seek to disrupt recreational hunting or fishing, but to educate individuals on how they can do so without facilitating ecological harm. Hunters all over the United States are urged to choose nontoxic options for their ammunition as well as their fishing lures for the sake of the Bald Eagles and other raptors with which we share the ruggedly beautiful natural landscape of this country.
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