It looks like another bad year for avian botulism in northern Lake Michigan. In the last week or so, hundreds of dead loons have washed ashore from Sleeping Bear Dunes north to the Upper Peninsula.
Warm water temperatures and low lake levels are associated with outbreaks of avian botulism. And there have been both of those conditions this year.
“This is looking to be a very intense year,” says Dan Myers at Tip of the Mitt Watershed Council. He tracks reports of dead birds in Emmet County.
One volunteer who walks a beach near Harbor Springs found 40 red neck grebes and 33 loons washed ashore in one day.
Tec Cummings says the sight was disturbing. “It’s heartbreaking to find them, that many birds, because I’m only walking three or four miles of shore,” Cummings says.
A research team monitoring Sleeping Bear Dunes Lakeshore reports three hundred dead loons plus other shorebirds in the last week. Tests of three birds so far confirm the toxin from type E botulism is present.
It’s thought that changes in the food web caused by invasive mussels create conditions that spread the toxin to fish and shorebirds. Steven Riley head of the U.S. Geological Survey team at Sleeping Bear says scientists haven’t been able to confirm the pathway by which botulism toxin gets from the bottom of the lake into shorebirds.
“It’s like a needle in a haystack type problem actually figuring out where the stuff is coming from,” Riley says. “But we’re doing the best we can. It’s difficult of course with weather issues and it’s very deep right off Sleeping Bear, 300 to 400 feet deep.”
This wave of avian botulism coincides with migrating birds coming through the region. Depending on weather conditions, the die-off could continue through November or taper off.
The worst outbreaks in northern Lake Michigan happened in 2006 and 2007 when six to eight thousand shorebirds died.
Type e botulism is not a threat to humans unless they eat raw fish or birds that are affected.