Botulism is Killing Great Lakes Birds
Counting dead birds along Lake Michigan’s Upper Peninsula shoreline last November was mind-numbing, even emotional for wildlife biologist Joe Kaplan. Hundreds of loons, cormorants, gulls, long-tailed ducks and grebes were scattered across the sand, washed up and rotting.
Then he spotted a familiar bird. The yellow band on its lifeless leg showed it was C3, a loon that had lived for 14 seasons at Seney National Wildlife Refuge in Michigan’s Upper Peninsula. The adult male was 22 miles from the refuge, headed for his warmer winter home, when he was caught in a botulism plume spawned by foreign invaders — two species of mussels and round gobies, a fat minnow-length fish.
Kaplan and other researchers say as many as 8,000 native and migrating waterfowl — including 2,000 loons, cherished for their haunting, sweet calls — may have died of toxic type E botulism along the lake’s northeast shore last fall, the second die-off in two years on Lake Michigan from the neurotoxin.
The outbreak also claimed four endangered piping plovers and at least one bald eagle.
The creatures likely ate botulism-infected gobies, a bottom-feeder susceptible to E botulism. Scientists say they think the botulism, which is native to the Great Lakes, comes to life in rotting cladophora algae and is absorbed by invasive zebra and quagga mussels that have taken over the lake bottom. Gobies eat the toxic mussels, and the birds eat the gobies.
Until 2006, there hadn’t been a major bird die-off from E botulism in Lake Michigan in more than two decades.
The interaction of the algae and the three invaders, which came from their native Black Sea in ocean ships’ ballast water, has given birth to a new cycle of deadly botulism. As the critters spread, so does E botulism.
Scientists say the die-off in Lake Michigan is likely to be repeated this year and to spread to areas including Lake Huron.
More than 50,000 birds have perished in E botulism die-offs on Lakes Erie and Ontario since 1999. No humans have been affected — cooking the meat of fish or ducks, for example, kills the botulism — nor has the problem spread to inland lakes.
The life of C3
Doting father C3 had stayed behind at Seney as other loons left, to tend to his chick, hatched in July — late for a loon chick.
He’d been banded in 1993 as an adult at Seney and spent each spring, summer and early fall through 2005 there with the same mate, the longest pairing ever recorded at Seney, said biologist Damon McCormick.
They broke up between 2005 and 2006 when he found a new mate (his ex took up with one of their sons). Loon parents share chick care equally, and C3 helped raise 17 chicks before his death, a refuge record.
To see the much-studied C3 as one of the botulism victims was moving for Kaplan.
“It gives you an odd sense,” he said, “that something is wrong in the lake.”
Something is wrong, said Tom Cooley, wildlife biologist for the Department of Natural Resources, who analyzes bird carcasses to verify that they died of E botulism.
“Once you have the right conditions, the botulism becomes more prevalent,” he said. “There’s no way to stop it.”
In 2006, biologists and volunteers counted 2,900 dead birds in a 14-mile stretch at Sleeping Bear Dunes National Lakeshore.
In 2007, the bird carcasses were spread over 400 miles of shoreline from Empire to Escanaba and on islands like South Fox and North and South Manitou.
No one knows the ultimate effect on bird populations. Many dead waterfowl likely were migrating from Canada, but some, like loon C3, were Michigan-based. Just how many loons were lost won’t be known until spring, when they should return to Seney and other nesting areas.
The unchecked spread of gobies and mussels, along with warmer water and lower lake levels, has created a dangerous soup, the biologists say. Lake Superior remains too cold for mussels.
But in the shallower, protected waters of Lake Michigan, gobies are so abundant they’re like ants on the lake bottom, said Mark Breederland, an educator with Michigan Sea Grant. Near the mouth of the Platte River, where the 2006 botulism die-off occurred, there are an estimated 40 million gobies.
Quagga mussels have created huge beds on the lake bottom, even outcompeting zebra mussels. While Lake St. Clair is infested with the invasive mussels and gobies, the botulism hasn’t been as big a problem because currents keep the water moving. The algae tend to grow best in still waters.
Cladophora algae bloomed in the Great Lakes in the 1960s and ’70s, nourished by phosphorus from fertilizer runoff and poor sewage treatment. Bans on phosphorus and improved sewage treatment reduced algae growth in the 1980s and ’90s.
Now, invasive mussels filter so much water they’ve made the water clearer, allowing the sun to penetrate deeper into the water and the algae to flourish. The mussels add another important ingredient to the mix — their feces fertilize the algae.
“There are a whole bunch of things happening on the lake bottom that are scary to a biologist,” said Ken Hyde, wildlife biologist for the Sleeping Bear Dunes National Lakeshore. “When birds start washing up onto the beach, it’s scary to the public.”