No cure in sight for loon-killing botulism
by Lacee Shepard
Northern Michigan is home to the call of the loon, but an outbreak of avian botulism has caused more than 1,000 deaths of the iconic northern bird.
In past years, loons sat lower on the list of birds affected by botulism. In 2006, when the bacteria began to have a noticeable effect on avian species, loons were the fourth most-affected, said Tom Cooley, a Department of Natural Resources disease lab biologist and pathologist.
In 2012, he said, loons catapulted to number one, with more than 1,000 deaths in the Sleeping Bear Dunes National Lakeshore area.
At this time there is an estimated loon population of 2,000, Cooley said. The bird is known for having high offspring mortality, he added, contributing to its difficulty in building population.
Botulism type E, or avian botulism, is “a paralytic condition in birds, fish and other wildlife caused by the ingestion of large quantities of the naturally occurring botulism toxin,” according to the Tip of the Mitt Watershed Council based in Petoskey.
Conditions already in the water create the perfect breeding ground for the bacteria to form, said Cooley.
“What algae can do is take oxygen out of the water and set up anaerobic conditions, with low oxygen or no oxygen,” Cooley said. “The botulism bacterium is a spore – forming bacteria and it proliferates under anaerobic conditions. It’s in the bottom segments of our Great Lakes.”
There are multiple theories about why loon death counts are rising. The bird’s predation on infected fish is a commonly offered reason.
“Loons are going to be out in deeper water,” Cooley said. “As the lake goes through a turn-over, you get a shift in the temperature and some bottom sediments are brought up and could be where loons are feeding.”
Last year was bad for loons. However, there have been few deaths reported so far this year, said Dan Myers, a water resource specialist at Tip of the Mitt Watershed Council.
Myers said he remains optimistic that there will be significantly fewer deaths this year since the prime time for most deaths has nearly passed.
Alec Lindsay, a Northern Michigan University biology professor who focuses on conservation of genetics, said most death occurs during the migration months, typically September into October. The bird typically migrates to the Atlantic coast near Florida.
Lindsay said there is still a chance the number of infected loons could rise this year as the migration period continues.
James Bull of Detroit’s Audubon Society said the loss of the loon would be upsetting for another reason.
“I think the bigger thing is this is part of our heritage – it’s the call of the North Country,” Bull said. “It would be such a deficit if you couldn’t hear that song on our northern lakes. It wouldn’t be just a biological issue – it would be a spiritual and psychological issue we would lose for future generations.“
Alice Vanzoeren, a former Traverse City parks volunteer, said if a loon is found on the shore it is most likely infected by the virus.
Botulism causes paralysis that prevents the bird from holding its head up in the water so it drowns and washes ashore. The only way to know if it has been infected is to have it tested.
Myers said there are no real solutions to stop avian botulism from infecting birds.
However, there are two ways to help prevent further spreading of the bacteria if a sick loon is found. One option is to remove the bird from the ecosystem by burying the bird 2 feet underground, said Myers. The second way is to put them in a trash bag and send them to a landfill for burial.