Thousands of dead birds will be collected from an Ontario shoreline on Monday as the province's Ministry of Natural Resources tries to determine what killed the waterfowl.

Officials estimate as many as 6,000 dead birds have washed up on the Georgian Bay's shoreline. The carcasses are scattered along a nearly three-kilometre stretch near Wasaga Beach.

"You just want to cry," resident Faye Ego told CTV Toronto on Saturday.

Authorities speculate that the birds may have been killed by a form of botulism after eating dead fish.

Locals said they noticed some dead fish on the beach a few weeks ago and a few dead birds earlier in September.

During Monday's cleanup, crews will be trying to tally up the total number of dead birds on the shoreline.

The Ministry of Natural Resources says it isn't unusual for large numbers of fish and other wildlife to die on the Great Lakes at certain times of the year.

According to the ministry, smaller-scale die-offs occur annually on the Lakes. The last one happened on Lake Ontario in 2007.

While several theories exist, residents in the Georgian Bay area say they want concrete answers.

"I'd like to get it cleaned up and figure out what it is, too," said resident Cindy Parkin. "It's pretty scary."

Public health agencies say no cases of human illness have been attributed to outbreaks of botulism in the Great Lakes.

Botulism thrives in low oxygen environments often found in zebra mussel colonies.

With files from The Canadian Press and a report from CTV Toronto's John Musselman