Ontario Provincial Police Const. Peter Leon said Saturday the number of dead waterfowl is estimated to be between 5,000 and 6,000.
The dead birds are scattered along a nearly three-kilometre stretch north of the community of Wasaga Beach, said Leon.
Federal and provincial officials believe the cause of the death is a form of botulism, apparently from the birds eating dead fish, he said.
Ministry of Natural Resources officials did not immediately return requests for information Saturday, but just two weeks ago they issued a news release saying the death of large numbers of fish and wildlife on the Great Lakes is not uncommon at certain times of the year. Georgian Bay is on Lake Huron.
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Type E botulism toxin is produced by a bacterium that lives in lake bottom sediment, and under certain conditions it begins producing the toxin, which then enters the aquatic food chain, according to the ministry. Birds who eat affected fish can die.
Health Canada says proper cooking and handling of food eliminates the botulism toxin.
Police say people in the area are being advised to keep a close eye on their children and pets to make sure they stay away from the dead birds.