Botulism killed the thousands of birds found on Georgian Bay earlier this month, Ontario’s Ministry of Natural Resources confirmed on Thursday.
Spokeswoman Jolanta Kowalski says a lab test on a bird from Christian Island showed it died of Type E botulism.
Ministry staff have picked up between 1,000 and 2,000 dead birds in the Wasaga Beach area, and results from seagulls are expected next week.
Kowalksi says such deaths are common in the fall and the ministry suspected botulism was the cause.
Though botulism is destroyed by cooking and is not a threat to humans, she warned residents to not let their dogs run loose as they might eat a carcass and become sick.
“It could continue for a few more weeks depending on water temperature [and] waves,” Kowalski said.
A decade ago, some 25,000 birds died from eating botulism-laced fish in Lake Erie.
With files from The Canadian Press