MINNEAPOLIS (WCCO) — A beautiful bird has made a comeback in the Midwest.

Once endangered, hundreds of trumpeter swans can now be seen along the St. Croix River near Hudson, Wis., this time of year.

But bird lovers are concerned for the swans’ health because of what the drought has revealed beneath the water and ice: lead. That unseen danger could impact the bird’s future.

“I have three deaths so far,” said Barry Wallace with the Wisconsin DNR.

Wallace monitors the birds for the DNR and sees the effects of lead.

“You’ll usually always see a bird separate itself, go off, all by itself, usually up on the ice shelf,” he said.

With water levels low, there’s concern many more will get sick.

The birds have to reach down in the river to get gravel that aids them in digestion. Sometimes, however, they ingest lead sinkers, which are used in fishing, that are mixed up in the gravel.

“These birds reach 4-5 feet down and just makes that much more lead available to them,” Wallace said.

The Wildlife Rehabilitation Center of Minnesota is currently treating seven birds with lead exposure.

“Trumpeter swans are called trumpeter swans because they have this big voice, and when they come in with lead poisoning they can barely croak,” said Phillip Jenni, the center’s director.

He plans to see between 20 and 40 swans this year, and only half will likely return to the wild.

“It’s really sad to see, because [lead poisoning] is a really slow decline,” he said.

Now those who work with the birds are trying to educate others.

“There’s nothing that can be done about the lead already on the bottom, but we can stop putting it in there,” Wallace said.

While lead birdshot was outlawed in the ’90s, people can still chose between lead and nontoxic sinkers for fishing.

If you see an injured swan, you should contact the DNR. It costs the rehabilitation center about $50 a day when a trumpeter comes in with lead poisoning.

And if they survive, they need up to three months of treatment.

If you’d like to help, visit the Wildlife Rehabilitation Center’s website.