GULLIVER - In a dramatic scene along the Lake Michigan shoreline in Schoolcraft County, researchers have recently discovered the carcasses of nearly 700 dead waterbirds, thought to be the victims of Type-E botulism.
Similar large Lake Michigan bird die-offs were recorded in the Upper Peninsula in October 2007 and downstate near Sleeping Bear Dunes National Lakeshore in 2006.
"During two weeks in mid-October, a seven-mile stretch of beach near Gulliver amassed 413 carcasses, including 236 common loons," said Damon McCormick a loon researcher from Common Coast Research and Conservation. "This episode was preceded by a September mortality event that primarily involved horned and red-necked grebes."
McCormick - who has researched loons at the Seney National Wildlife Refuge in Schoolcraft County - said the tally of 694 total dead birds included 247 common loons, 152 horned grebes, 98 red-necked grebes, 73 long-tailed ducks, 64 white-winged scoters and smaller numbers of ring-billed gulls, double-crested cormorants, red-breasted mergansers and herring gulls.
The dead birds numbered nearly 100 per mile.
"Although collected specimens have not yet been tested for Type-E botulism, the circumstantial evidence strongly suggests that the toxin is responsible for most, if not all, of the deaths," McCormick said.
Michigan Department of Natural Resources officials define Type-E botulism as a disease "that results when a toxin, produced by the bacterium Clostridium botulinum, is ingested, causing paralysis."
The DNR said the disease has been associated with waterbird and fish die-offs in Lake Michigan during recent years.
"Intoxicated birds may be lethargic, have difficulty holding their head out of the water or be unable to fly," the DNR said.
To the east of Gulliver - along a separate three-mile section of beach - 72 common loons washed ashore among 96 waterbirds killed during the mid-October die-off, McCormick said.
"Mirroring a pattern documented during previous outbreaks, all dead loons encountered in the eastern Upper Peninsula this fall have been breeding adults," McCormick said.
In late October 2007, passing motorists reported similar avian carnage, with hundreds of loons and other fish-eating birds - including cormorants, grebes and gulls - found dead along Lake Michigan in Mackinac County. At that time, the dead waterbirds were initially found between the Cut River and Point Aux Chenes over several days.
The 2006 avian death toll at Sleeping Bear Dunes National Lakeshore reached roughly 2,600 birds. Researchers think loons and gulls acquire the toxin by eating fish. They also think the factors determining toxin production vary from year to year, along with its availability to birds.
"Poisonings in humans from Type-E botulinal toxins usually are associated with eating uncooked, imperfectly canned and improperly preserved fish and marine animal products," a DNR-Sea Grant notice read.
The DNR recommends waterfowl hunters in the eastern Upper Peninsula and northern Lower Peninsula follow these precautions when processing waterfowl:
Harvest only waterfowl that act and look healthy.
Wear rubber, plastic or disposable gloves while field dressing, skinning or butchering waterfowl.
Remove and discard intestines soon after harvesting and avoid direct contact with the intestinal contents.
Wash hands, utensils and work surfaces before and after handling any meat.
Keep waterfowl cool (either with ice or refrigeration), below 45 degrees (F), until butchered, then refrigerate or freeze.
Cook waterfowl to an internal temperature of 165 degrees (F). Cooking may not destroy the botulism E toxin.
According to the DNR, the first waterfowl die-off attributed to botulism in Michigan occurred in 1941 when about 1,000 wild ducks and shorebirds died near Monroe from Type-C botulism in the Lake Erie marshes.
The first Type-E botulism die-off was in 1963.
"Prior to this die-off, Type-E botulism was not know to exist in wild birds in North America," the DNR said. "The 1963 die-off extended from the Indiana border to Leelanau County, nearly the entire Lake Michigan shoreline of the Lower Peninsula."
The DNR said the estimated mortality in 1963 was 7,720 birds, including 3,300 loons, 4,290 gulls and 130 miscellaneous birds. The following year, another 4,920 birds - including 3,570 loons, 820 gulls, 200 grebes, 240 ducks and 30 miscellaneous birds - were killed in a northern Lake Michigan die-off from St. Ignace to Wisconsin between August and October.