Despite dozens of dead loons, it's a mild year for avian botulism

Oct 21, 2019

Dozens of dead loons washed up at Sleeping Bear Dunes National Lakeshore last week. On Friday afternoon, the official carcass count was 32.

The birds likely died of type-E botulism, a bacterial disease that paralyzes and kills them. It will take a few weeks for lab results to confirm their cause of death. 

Erica Plesha leads the avian botulism crew at the park. She says bird deaths often spike in October, and that recent strong winds and waves may have washed the birds in.

"This was a little bit out of the blue, but not completely surprising given the time of the year, given the storm events," says Plesha.

High water levels are linked to lower botulism mortality, and according to Plesha, the number of bird deaths is still low when compared to other years.

"In 2012, in the month of October, there were 694 in one month," she says.

Avian botulism has become more common in the Great Lakes since the invasion of quagga mussels. Despite this year's relatively low numbers, climate change is expected to increase instances of the disease overall.

The National Park Service has published recommendations on what to do if you find a sick bird.