Three of our iconic Northwoods bird species are being killed by lead picked up during feeding activities. They are the American bald eagle, the common loon, and the trumpeter swan. Lead also takes a toll on at least 12 other Wisconsin bird species.
The impact of lead on our wildlife is documented repeatedly at wildlife rehabilitation centers around the Midwest that do their best to save those birds affected from an agonizing lead poisoning death. The Wild Instincts Wildlife Rehabilitation Center in Rhinelander recently reported that 96 percent of the bald eagles they received this fall have lead poisoning. Sue Kartman, who volunteers at our Nature Education Center and volunteers as a driver for Wild Instincts to transport sick bald eagles to their Rhinelander facility, says that many eagles she transports are suffering from lead poisoning. It is very costly and time-consuming to treat and rehabilitate affected birds and it is often unsuccessful.
The Wisconsin Department of Natural Resources (WI DNR) just released the results of its 2019 bald eagle survey. It found 1,684 occupied eagle nests in 71 of 72 counties in 2019, with all but northwestern and west-central Wisconsin experiencing increases. Overall, researchers documented 11 fewer active nests than the record 1,695 found in 2018. An occupied nest is a nest with an incubating adult, eggs, young or a repaired nest.
Bald eagles have made a big comeback in Wisconsin since the banning of DDT in 1972. Now that eagles are doing well in Wisconsin, there are still at least two other threats taking a toll on bald eagle populations. They are, impacts with vehicles when they are feasting on road kills and lead picked up while feeding on animals killed or wounded with lead bullets or shot.
For the past 40 years, lead exposure and lead poisoning have been major health issues for bald eagles received by or admitted to The Raptor Center at the University of Minnesota. The statistics are alarming. Ninety percent of all bald eagles received each year at the Center, about 120 to 130, for all types of problems have elevated lead residues in their blood. And, 20 to 25 percent have sufficiently high lead levels to cause clinical lead poisoning. Most of these birds die or must be euthanized. Gathered data over the years clearly indicated that spent ammunition from both shotguns and rifles was the source of lead exposure.
The cumulative lead poisoning data led to the passing of a 1991 federal law that banned the use of lead ammunition for waterfowl hunting. But that wasn’t the end of the story. The prevalence of poisoned eagles didn’t change much even though there was documented evidence of good hunter compliance with the law.
The Raptor Center conducted another 13-year retrospective study of lead poisoning and they found that spent lead from deer hunting as the primary source of lead poisoning when bald eagles feed on the remains of deer killed by hunters.
There was conclusive evidence that spent ammunition in deer remains is a significant if not primary source of lead toxicity. There is also direct evidence that some cases of poisoning are due to shotgun pellets that are imbedded in waterfowl and small upland game, such as pheasants, squirrels, and rabbits, that may be wounded and subsequently consumed by eagles and other raptors.
Lead poisoning in water birds, predatory birds and scavengers is still common even though lead shot for waterfowl hunting has been banned. For example, common loons, the state bird of Minnesota, continue to be impacted by lead when they ingest fish, they swallow them whole, who have swallowed lead fishing tackle. A study in New Hampshire found that 49 percent of 253 necropsied loons were victims of lead poisoning—and fatalities were the highest during peak fishing season. Jigs accounted for more than half of the lead fishing tackle objects found in loons. Loons also pick up lead pellets and discarded lead tackle along with small stones for use in their gizzards to help them digest their food, often with fatal results. One lead pellet can kill a loon and even a trumpeter swan, the largest waterfowl in North America!
Trumpeter swans are soaring back successfully in Wisconsin after WI DNR biologists and others began reintroducing them in the late 1980s after a long absence, but they too are impacted by lead poisoning. A comprehensive review of trumpeter swan mortalities indicate that 25 percent of swan mortalities are a result of lead poisoning.
The problem is, there has been a lot of lead used over the years to hunt waterfowl and upland game and anglers have used lead fishing tackle for generations. Some of that lead remains in the environment for a long time and will continue to have a lethal impact on wildlife that consume it.
Here is what we can do to reduce or prevent lead poisoning in wildlife. Because lead is readily available and cheap, it will take a major change in the law and the hunting and fishing culture to stop or reduce the unnecessary deaths caused by lead. To make this change, we need to educate the public of all ages about lead’s deadly impact on wildlife and how to prevent it by GETTING THE LEAD OUT! Studies have shown that switching to non-toxic ammunition can help susceptible bird populations and the environment. Deer hunters should be encouraged to use non-toxic copper ammunition. People fishing could use lead-free tackle and dispose of lead tackle properly, certainly not in a lakes, rivers, or trash cans, but at a hazardous waste collection center or at a scrap metal collector/recycler.
Using safe, lead-free alternatives for fishing and hunting may cost a bit more, but it’s worth it if we can prevent unnecessary, painful deaths of susceptible species that we enjoy seeing in the wild.