For several weeks, residents and workers around the area known as "The Forks," where the Assinboine and Red Rivers meet, have reported seeing dead ducks and unusual behavior among the birds, the Winnipeg Sun reported Thursday.
"On shore, the ducks seem like they're drunk, because they stumble around and don't seem to know where they are or what's happening," 60-year-old area resident Wayne Williams told the Sun.
Jeanella Budge, who works at a refreshment stand, told the newspaper she's seen more than 100 dead ducks floating in recent weeks.
"At times, the ducks that seem healthy have been seen picking on the sicker ones and trying to drag their heads underwater," she said.
Provincial conservation officials said tests had shown the cause was viral avian botulism, which attaches to natural bacteria and is fatal to water birds, the Sun said.