TRAVERSE CITY — Dead birds are nothing new to Julie Melottie. Her job requires her to see plenty of them, and the fall season often finds her sifting through flocks of feathered remains.
Melottie is a lab technician for the Michigan Department of Natural Resources wildlife disease lab in Lansing, where among other chores she conducts tests to determine whether birds have fallen victim to avian botulism.
She performed such a test on Tuesday to determine what killed bald eagles collected from Leelanau and Manistee counties.
She’s bracing for more tests, particularly among water birds like gulls and the iconic loon, if this season’s avian botulism outbreak is anything like what occurred in 2012.
“Last year was a big year it,” Melottie said.
Avian botulism killed tens of thousands of birds around the Great Lakes region since the 1950s, and more than 10,000 in 2006 and 2007 alone. Each year, corpses of infected loons wash up on the beach along the Sleeping Bear Dunes National Lakeshore in Benzie and Leelanau counties, often in late October and early November. Last year volunteers reported finding 580 dead loons along that stretch of Lake Michigan.
“You’ll see birds that are severely affected will have wings out, laying on the beach, and (their head will be) bobbing down or their bill will be touching down in the sand,” said Dan Ray, the project leader for avian botulism monitoring at Sleeping Bear Dunes.
Scientists believe invasive mussels may be to blame. Mussels filter lake water, which allows sunlight to penetrate deeper into the lake and cause thick blankets of algae to grow. As the lower layers of algae decompose, they provide the perfect environment for Type-E botulism bacteria to grow and produce a toxin.
The bacteria eventually enter the food chain, infecting the invasive gobi fish, which the birds eat.
Botulism eats away at birds’ nervous system, first affecting their ability to close their wings and then progressing to the point where they have trouble breathing and their hearts fail. Most affected waterfowl swim offshore to seek protection from predators, but the move kills them when they can no longer hold their heads above water.
Thousands of birds can wash ashore some years; other years, such as 2008 and 2009, few signs emerged of a botulism infection.
Ray said anyone who observes dead or afflicted birds should stay away and call a local authority. Ray and others at the National Park Service try to bury the birds to keep scavengers and pets from becoming infected, since botulism travels between organisms through consumption.
It’s too soon to tell what sort of year 2013 will be, though August death rates were half what they were last year. Experts hope cold nights and cool water temperatures will push the birds to migrate south faster, avoiding major infection.
Unlike mussel-filtered water, the science is still unclear. That’s why there are several studies being performed by the U.S. Geological Survey and National Park Service to learn more about the toxin.
“We need to know more about how the toxin is getting from these microorganisms into the food that the loons eat,” said Sheridan Haack, a research hydrologist at the USGS Michigan Water Science Center.
Haack is working to analyze the gene that causes the bacteria to be toxic. Another USGS study based in Wisconsin is trying to determine where in the lakes the birds are picking up the bacteria.
“If we understand what’s happening, how the toxin is getting into the birds and understand more about why we sometimes have outbreaks and other times we don’t … (T)hen we might have a better chance of seeing if there’s something we can do to keep the birds from acquiring this toxin,” Haack said.