What is Avian Botulism
Loons, scoters, grebes, and piping plovers are among thousands of birds found dead on the Lake Michigan shoreline in recent years. Type E botulism has been confirmed as the cause of death by the Michigan Department of Natural Resources (MDNR) in bird carcasses collected from numerous locations along the Lake Michigan shoreline. Each fall, reports of dead birds from Grand Traverse Bay to Sturgeon Bay are phoned in to the Tip of the Mitt Watershed Council office, where staff respond and work with Michigan Sea Grant and the MDNR to track bird and fish fatalities in 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 Director 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 the bird kills, Cronk explains that "when we get calls about dead birds, we inquire into and record relevant information, such as the number and type of birds, but we also take the opportunity to educate the public about avian botulism and precautions that should be taken.”
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. Following this decades-long hiatus, botulism returned with vehemence, taking a heavy toll on migratory waterfowl with nearly 3000 dead birds reported from just Sleeping Bear Dunes National Park in 2006 and an estimated 8,000 dead birds turning up on the northern Lake Michigan shoreline in 2007. During the relatively cool summers of 2008 and 2009 with Great Lakes’ water levels rising slightly, the incidence of avian botulism dropped dramatically and few dead birds were reported. Unfortunately, the quiet was not to last. Scores of dead birds began to appear again on the northern shores of Lake Michigan in the fall of 2010, following a summer of warmer temperatures and a return to lower water levels.
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".