December 31, 2013 at 6:20 pm #1908MikeKeymaster
Bird die-off shows fragility of ecosystem
December 8, 2010
As they do every autumn, hundreds of thousands of loons, gulls, grebes and other migratory birds are making the journey from the vast wetlands of Canada to the Great Lakes.
For thousands of these birds, the journey will end in gruesome death.
In what has become an annual rite of autumn, the carcasses of migratory birds are washing up on the shores of the Great Lakes. Although biologists remain uncertain what is killing the birds, the No. 1 suspect is avian botulism.
In layman’s terms, the birds are being poisoned.
“It’s killing a lot of birds that are important to us,” Michigan conservationist Joe Kaplan told the Chicago Tribune last week. “This is a very serious problem that deserves more attention.”
In the past 15 years, an estimated 100,000 fish-eating birds have died in the Great Lakes, including threatened and endangered species such as common loons, bald eagles, Caspian terns and piping plovers.
First noticed in lakes Ontario and Erie, the die-offs have moved north and west. The upper reaches of Lake Michigan forms the epicenter of the plague this year.
A growing body of evidence connects bird deaths to Type E botulism, a compound found naturally in bacteria spores. These spores settle onto lake-bottom sediments and become toxic under the proper conditions of relatively warm water and low oxygen.
The toxins are consumed by filter feeders such as zebra and quagga mussels, which in turn are eaten by round gobies. Gulls, cormorants and other fishing-eating birds feed on the poisoned gobies.
Death comes quickly and violently. Paralyzed by botulism, the birds drown. Their poisoned carcasses wash ashore and become food for scavengers such as eagles, foxes and coyotes, which are the next to die.
While botulism-related bird deaths have been known throughout history, only in recent years have they become epidemic in the Great Lakes. It is yet more evidence linking invasive species — round gobies, zebra mussels and quagga mussels all arrived in the past 22 years — to this dire threat.
“Loons are such a beautiful bird, and to see a hundred of them lying on the beach, it just really disturbs people,” says Harry Leslie, who oversees a state park near Erie, Pa.
It also serves as yet another reminder of why we must redouble our efforts to protect the Great Lakes from alien species such as Asian carp. Too often, we don’t truly appreciate the peril until it is too late.
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