The last major outbreak of avian botulism on Lake Michigan was in 2016, when hundreds of dead birds washed up on shore. The bacterial disease has affected waterfowl like loons and mergansers in the Great Lakes for decades. But high water levels on the lakes are good news for the birds, at least temporarily.
Birds can't wash up without a beach
At Sleeping Bear Dunes National Lakeshore, a team of volunteers walk 32 miles of beach every week, from June through November. They’re collecting data on avian botulism, a disease that paralyzes and kills waterfowl. It’s caused by bacteria that produce a toxin in the water.
Mary Ellen Newport is out for her first walk of the season.
“We document all the living birds and any dead or sick birds," she says.
Newport is a science teacher at Interlochen Center for the Arts. The mile-long section of beach she’s responsible for monitoring starts at the mouth of the Platte River. She has to cross it and go south.
“Yeah we usually wade across over that way, and we can get through like it's up to the hips," she says. "Now we're gonna do something different."
This year, water levels on Lake Michigan are so high that the river mouth is impassable on foot. So, Newport is going to use a canoe.
"There’s another way to come in from the south side, but that turns into a 4-mile hike, so this is the lazy person's way to take the canoe across," says Newport.
High water levels are making botulism monitoring difficult this year. Some beaches have become bluffs where dead birds can’t wash up. Some sections of shoreline may not be monitored at all if volunteers can’t access them.
"They've undermined the entire food chain"
Avian botulism deaths have been down in Sleeping Bear Dunes since 2017. But overall, the disease has been worse on Lake Michigan in recent decades -- ever since the invasion of quagga mussels.
Newport says what’s so disturbing about Lake Michigan’s botulism problem is that it shows an ecosystem in upheaval.
“The quaggas and the zebra mussels have undermined the entire food chain, so it’s about way more than avian botulism," she says. "It’s about the health of the entire Great Lakes.”
These filter-feeding mussels make the water clearer. Clearer water lets in more sunlight. Sunlight fuels the growth of cladophora, that annoying, smelly algae that washes up on the beach.
When cladophora dies and decays, it creates the perfect environment for bacteria to produce the botulism toxin.
Short-term good news
High water levels are tough for monitoring, but they can actually be good for the birds.
Scientists don’t know the exact mechanism, but botulism outbreaks are linked to low water and warm temperatures. It's thought that warm water promotes the growth of the botulism bacteria.
The water levels link, according to the DNR's botulism manual, is "likely is related to warmer water and sediment temperatures during low water events."
So, Newport says this year’s high water and colder lake temperatures are good news for the affected birds.
“We should have a good summer," she says. "So I'm not unhappy about the high lake levels for the botulism count."
Unfortunately, it’s probably temporary. Scientists expect climate change to keep warming the Great Lakes, which could increase bird deaths from botulism long-term.
