Dozens of dead grackles found on King Street in August were poisoned.
A provincial spokeswoman said this afternoon that toxicology results found evidence of the chemical anticholinesterase, commonly used in materials for controlling pests by affecting the nervous system.
The birds were found in early August outside the Ma Mawi Wi Chi Itata community centre on King Street, while about 20 more were found on the roof of the buildings, some dead and others twitching.
The province said there have been no other reports of unusual bird deaths.
While there are laws prohibiting the poisoning of domestic birds and some wild species, there is no legal protection for grackles.
The provincial spokewoman said grackles are not considered migratory birds and, as a result, are not protected under Manitoba’s Wildlife Act.