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What is Avian Botulism
Loons, mergansers, grebes, and piping plovers are among thousands of birds found dead on the Lake Michigan shoreline this year. Type E botulism has been confirmed by the Michigan Department of Natural Resources (MDNR) in specimens collected from Sleeping Bear Dunes National Lakeshore in the south to Wilderness State Park in the north. Tip of the Mitt Watershed Council has received numerous phone calls reporting dead birds from Grand Traverse Bay to Sturgeon Bay and is working with Michigan Sea Grant and the MDNR to report affected areas.
"This is a tragic loss of birds that we in Northern Michigan have come to identify with" commented Kevin Cronk, Monitoring and Research Coordinator at Tip of the Mitt Watershed Council. Cronk added that "we are deeply concerned about this situation and the number of problems plaguing the Lake Michigan ecosystem." In regards to Watershed Council response to recent bird kills, Cronk reports that "information regarding dead birds in Northern Michigan is being recorded by Watershed Council staff and shared with agencies like Sea Grant and the DNR to track the extent of the problem."
According to the MDNR, botulism is a "paralytic condition brought on by the consumption of a naturally occurring toxin produced by the bacterium Clostridium botulinum." Type E botulism is found in anaerobic (or low oxygen) environments, such as lake sediments, where it is taken in by fish. Affected fish experience a loss of equilibrium and exhibit unusual behavior such as swimming erratically or floating near the surface. These fish become easy targets and birds feeding on dead or dying fish are in turn affected. Great Lakes fish that have been affected by botulism include freshwater drum, smallmouth bass, rock bass, stonecats, round gobies, channel catfish, alewives and sturgeon.
Avian botulism was first documented in the Great Lakes in the 1960's, but there were no confirmed cases in Lake Michigan between 1983 and 2006. Last year, the bird kill was limited to a small geographic area in Benzie and Leelanau counties, Ken Hyde from the National Park Service reported that "Sleeping Bear Dunes lost approximately 2900 birds in 2006". This year Hyde reports lower numbers with just over 1000 dead birds documented in the same area. However, the geographic range of the epidemic has grown considerably with dead birds being reported up and down the coast from Sleeping Bear Dunes to the Straits of Mackinac.
Although uncertain, recent outbreaks may be linked to lake ecosystem disruptions caused by low lake levels and aquatic invasive species, such as the zebra mussel and round goby. The bird kills also occur in waves, depending upon environmental conditions. Recent die offs on the Lake Michigan shoreline are believed to be the result of autumnal changes in the lake ecosystem combined with the fact that a great number of birds are migrating through the region. The current outbreak poses little danger to people since most bird species affected are not typically eaten by people and thorough cooking destroys the toxin. However, Cronk advises that "everyone take precautions if handling dead birds by using disposable gloves and washing thoroughly afterward." Cronk also warns that "anglers and hunters should avoid fish and waterfowl that are easy pickings due to strange behavior, such as lethargy and erratic swimming" and that "all fish and game should be cooked thoroughly so as not to take any chances".