What’s killing the birds?
From the Grand Rapids Press, Nov. 28
Avian botulism returned to Lake Michigan this year, killing more species and lasting longer than other recent outbreaks, according to state wildlife officials and researchers.
The increase came after a two-year lull.
The outbreaks first hit Sleeping Bear Dunes National Lakeshore in Benzie and Leelanau counties in 2006. The die-offs rapidly spread across northern Lake Michigan shorelines and killed an estimated 8,000 to 10,000 birds in 2007.
The outbreak subsided until this year, said Joe Kaplan, a biologist with Common Coast Research and Conservation, a nonprofit organization.
“What’s happening this year is a major event. It looks like the area of impact was highest in Mackinaw, Schoolcraft, Emmett and Antrim counties,” Kaplan said.
CCRC helped coordinate beach monitoring efforts for the dead birds, which numbered 50 per mile near Cross Village and Wilderness State Park.
Scientists are unsure what causes the outbreaks. They theorize the naturally occurring toxins that thrive an oxygen-deprived environment are created by rotting mats of cladophora algae. Those toxins are concentrated in quagga and zebra mussels that filter the water.
The toxin likely is passed to birds that eat the mussels or feed on fish such as round gobies. The round gobies eat the mussels. The birds become paralyzed, drown and wash ashore.
The 2006 and ’07 die-offs began in June and lasted through the fall. Cormorants, grebes and ring-billed gulls died in the early part of the season. Migrating birds such as long-tailed ducks, white-winged scooters and loons died later in the season.
Kaplan said bird mortalities in 2008 and ’09 were fairly low and ceased during the fall.
Tom Cooley, a biologist with the Department of Natural Resources and Environment’s disease lab, said experts do not know why the outbreaks lingered into the fall this year.
The outbreaks have caused sporadic reports late into the season from Sleeping Bear Dunes, Beaver Island, and Leelanau and Antrim counties.
“We’re probably not going to be too far away from 2006 when we had about 3,000 in estimated mortality,” Cooley said. “When we get into the fall, you get into the migrants that are using the open water.”
Kaplan said a large number of grebes died this year. Horned and red-necked grebes are believed to shed their flight feathers in the open waters of northern Lake Michigan.
Reports of dead birds at Sleeping Bear Dunes following an October storm suggested they, too, likely died a considerable distance from the park’s shoreline near Empire, said Chris Otto, a biological technician at Sleeping Bear.
“In 2007, we were finding a lot more incapacitated birds in the process of dying. The difference this year is when the big event hit with the storms, these birds were well dead and scavenged,” Otto said. “They died somewhere other than the immediate area.”
Through Nov. 1, 663 dead birds were found at Sleeping Bear, he said.
In mid-June, the Sleeping Bear Dunes held informational meetings for volunteers interested in participating in the National Lakeshore’s beach monitoring program. In a press release, the Park stated:
In addition to actively monitoring the shoreline for sick and dead birds, the park is collaborating with scientists from the U.S. Geological Survey, the University of Wisconsin-Milwaukee, the University of Michigan, and Northwestern Michigan College’s Water Studies Institute, to conduct studies in the Lake Michigan nearshore environment to better understand the mechanisms of toxin transmission. Many of these studies are funded through President Obama’s Great Lakes Restoration Initiative to assure that Great Lakes beaches, fish, and sources of public drinking water are safe, and that the ecosystems that fish and wildlife depend upon are healthy.
