Eagle's comeback masks silent killer
UPPER SIOUX AGENCY STATE PARK -- Eagles were only migratory visitors when Terri Dinesen took on her role as manager of the Upper Sioux Agency State Park on the Minnesota River in 1991.
Today, she is using GPS to mark the locations of eagle nests that can be found in the region. Eagles have re-established themselves here, and the number of eagles following migratory waterfowl each year has definitely increased as well: She spotted 17 eagles all perched on one large tree over the river just this week.
But one thing has not changed: Throughout these years, Dinesen has served as a licensed rehabilitator for injured wildlife. Every year, she receives anywhere from three to five calls to come and pick up sick or injured eagles.
In many cases the symptoms are all too clear. The birds are lethargic, and unlike birds weakened by a virus or injury, they do not have their mental wherewithal. They do not attempt to flee from the grasp of the two-handed predator they would normally fear.
Dinesen knows that in most cases, the eagles are the victims of lead poisoning.
In some cases, it's because the birds have been struck by lead shot. Like time release capsules, the lead bb's embedded in the birds release their toxin.
More often, it's because the birds have ingested lead by devouring the carcasses of animals shot by hunters.
She delivers the eagles to the University of Minnesota Raptor Center.
The prospects for survival can be poor once an eagle has ingested lead fragments.
"I don't think a single one of the eagles that we know ingested it have made it,'' said Dinesen of the eagles she's retrieved.
The Raptor Center receives about 100 eagles a year from around the state, according to its executive director, Julia Ponder, D.V.M.
Eighty percent of the eagles have some lead in their systems, and in recent years, 25 to 33 percent of them have toxic levels of lead at 0.2 parts-per-million or higher.
Ponder said one thing has been obvious and well documented. The number of eagles reaching the center with toxic levels rises in November with the firearm deer season. The birds are scavenging on the gut piles of deer with lead bullet fragments.
Dinesen and Ponder are among those who see a problem otherwise invisible to most, hidden as it is by the success story of the eagle's comeback in North America.
The state's bald eagle population has certainly rebounded in the last two decades, noted Lisa Gelvin-Innvaer, non-game program specialist with the Department of Natural Resources in New Ulm.
She pointed out that her predecessor once had the assignment of finding the only active eagle nest in the entire region.
In more recent years, there have been surveys showing nesting pairs of eagles along much of the Minnesota River from New Ulm to Ortonville, and evidence that the majestic birds have been expanding their nesting range along tributaries as well.
But few people see ill eagles, in part because they avoid people and once weakened or made ill, quickly become prey themselves. Ponder said the eagles reaching the Raptor Center for care represent merely the tip of the iceberg.
She said the evidence is clear that lead from hunter's spent ammunition takes the greatest toll on the bird that is our national symbol. In contrast, lead fishing tackle is the cause of most lead poisoning in loons.
While the Raptor Center sees its greatest increase in lead-poisoned eagles after the deer firearm season, Dinesen said lead poisoning is a problem during every season.
Just a couple of years ago she was called to retrieve a sick eagle near Hawk Creek. The eagle was part of a nesting pair that the owners of the land had been watching when to their dismay the female bird took ill and stayed on the ground.
Dinesen spotted the eagle near the carcass of a wild turkey it had been feeding on. The turkey had been killed by lead shot, and the lead levels in the eagle were just off the chart, said Dinesen.
For now, all she and others can do is work to educate the public about the danger. She makes a point of engaging fishermen and women at the state park in conversations about the issues of lead tackle. She has no way of knowing whether the anglers are changing to lead-free tackle as a result, but Dinesen said there is no doubt that there is a growing awareness about the dangers of lead in the environment.
Matt Holland, senior field coordinator with Pheasants Forever, served on a state commission that looked at the issue of lead poisoning. He agrees that there is more awareness of lead issues among hunters too.
Holland would like to see more research undertaken. He points out that the issue of lead poisoning in eagles is not as acute of a problem as was once the case with waterfowl poisoned by lead shot.
But he also said that change is coming, and he's among those making it. He now makes it a practice to use the same steel shot as required for waterfowl when hunting pheasants, if only because it's now required for any type of hunting on federal waterfowl production lands.
Ponder also hopes to see more research completed. While we know the devastating neurological effects of toxic levels of lead in eagles, she said research is needed to know what the long-term consequences of low levels of lead might be in the birds. We have no idea right now, but we do know that low levels of lead in people can host a wide range of health problems, she explained.
Ultimately, it's all part of the issue of what lead in the environment means for people and wildlife, according to Gelvin-Innvaer. "We're a part of the environment, not apart from it,'' she said.