© Connormah/Wikimedia CommonsAmerican coot
An estimated 200 dead American coots recently have been sighted near Dubuque's Lock and Dam No. 11 on the Wisconsin side of the Mississippi River.

Fishermen observed the dead birds near O'Leary's Lake, located near Eagle Point Road, off of U.S. 61/151.

Coots are dark-gray to black in color, with a bright-white bill and forehead. Duck-like in many ways, they are members of the rail family in the same avian order as cranes.

"They're not much good for anything. Some people eat them," said Carl Hanson, owner of the Eagle Point fishing barge, who saw the dead birds floating in the water.

The deaths aren't that unusual. This is the seventh time since 2002 that waterfowl die-offs have been documented on the upper Mississippi River, and each time prior, trematodes were responsible, officials said.

© Mike Day, Telegraph Herald A coot swims in the tailwaters of Lock & Dam No. 11 while anglers try their luck on the Iowa side of the Mississippi River this morning.
Trematodes are a parasitic flatworm that spends part of its life inside snails. Waterfowl die from trematodes each year, but in years when snail populations are high, mortality rates of snail eaters -- American coots and lesser scaup -- increase. The invasive faucet snail is an intermediate host for three types of trematodes.

Wisconsin Department of Natural Resources officials are tracking the situation.

"This is very likely the result of trematodiasis, a nearly annual event caused by diving ducks (primarily coot and scaup) feeding on a snail that hosts the trematodes," said Dan Goltz, a DNR wildlife biologist in Boscobel. "My understanding is that the coots are getting sick and dying up in the pool (11). They float through the lock and dam, and the path of the current carries many of them into O'Leary's Lake. Changes in water levels can deposit them in locally heavy concentrations."

The DNR has gotten several phone calls about the birds' deaths.

"Unfortunately, there's nothing we can do about it," Goltz added.