A growing number of trumpeter swans, nearly extinct 50 years ago, are falling sick from lead poisoning on the St. Croix River.
The majestic birds, largest of all waterfowl, have been plucking lead fishing sinkers from open water near Hudson, Wis. While the lead problem isn't considered extensive enough to threaten the swans' revival, consumption of lead often results in death, and it's also causing sickness elsewhere in the food chain.
"I think it's a serious issue for the swan population," said Phil Jenni, executive director of the Wildlife Rehabilitation Center of Minnesota. "Anybody who really cares about other living things ought to be concerned."
Several swans have been found dead along the St. Croix this winter. Dozens of others are under the care of Jenni and his staff, who try to reverse the blood-tainting illness that weakens them.
"It's a terrible thing seeing an animal suffering from lead poisoning," Jenni said.
The accumulation of lead in the St. Croix isn't anything new, but swans find it quicker in drought years when river levels fall. Swans foraging for aquatic plants and crustaceans consume lead sinkers and lead shot when they swallow gravel to aid in digestion.
"That bottom has to be virtually covered with lead," said Barry Wallace, a Hudson resident who has been a volunteer swan monitor for the Wisconsin Department of Natural Resources for 23 years. Swans tend to congregate in winter at the mouth of the Willow River, which feeds into the St. Croix just north of Hudson. "This is one of the most popular fishing spots on the whole river. We've all fished it, all of our lives."
Wallace said he's found swans wrapped in fish line and stuck with hooks, but he said the real hazard is lead, which never goes away. Lead shot from hunting 100 years ago still can be found in shallow marshes nearby, he said.
"This just isn't the hot spot and an isolated area; it happens all over the state and the country, really," Wallace said.
Evidence of lead has been found elsewhere in the food chain as predators such as eagles feast on dead swans.
"There's nothing we can do about that, but we can stop putting it in there now," he said of lead that many anglers use. "I've always believed sportsmen should be out in front on conservation issues."
More non-lead fishing tackle is sold now, and all anglers should make a conscious effort to buy it, he said.
Trumpeter swans were heavily hunted in the United States many years ago, both for their meat and their feathers. By the 1880s, they were gone from Minnesota, and they had dwindled to only 69 birds, all of them in Montana, by the 1930s. Efforts to reintroduce them in Minnesota began in the 1960s.
Now Minnesota has about 4,000 swans, and Wisconsin and Iowa have growing populations as well, Jenni said.
"It's really a parallel to the bald eagle," he said. "For me they're a charismatic bird. They're huge. They have the potential to get people to pay attention to wildlife and the environment. They have a way of grabbing people's attention."
Most large gatherings in the Minnesota vicinity occur on the St. Croix and open water on the Mississippi River near Monticello, Jenni said. Swans also forage for corn in farm fields in mild winters, but they're safer from predators when they feed on the river, he said.
The Wildlife Center, one of the nation's busiest wildlife hospitals, will treat as many as 40 swans this year. Most will have lead poisoning. Ten years ago the center treated on average five swans a year, but Jenni said it's possible the number of poisoned birds has grown at a pace proportional to their population. It's illegal to hunt trumpeter swans, but sportsmen also need to do their part to end the lead problem, he said.
"The lead that is out in the water now, in the environment, will be there for a long time," Jenni said. "For the culture and community, it matters. A lot of people live here and stay here because of our natural resources. We need to pay attention to that, to preserve it and protect it."
Kevin Giles • 651-925-5037 Twitter: @stribgiles