A group of ducks found dead in Jarry Park in the fall met their end after eating grain laced with a controversial bird-control poison, testing has revealed.

The mystery surrounding the death of more than a dozen ducks, whose bodies were found in a number of places in the park on one day in September, was solved after their remains were sent for necropsy and Avitrol-laced grain was found in their digestive tracts.

“The concentration found in the digestive system of the birds was significant enough to cause death,” Sophie Roy, spokesperson for the Quebec’s environment ministry, said in a statement sent to CBC News.

The city investigated when the birds were discovered, though ruled out water contamination after other ducks and fish in the pond were found to not have been affected.

Aims to scare off undesired bird flocks

Avitrol is a commercial pesticide that attacks a bird’s central nervous system. Birds that have ingested the substance behave oddly, and usually emit distress cries which are enough to scare off other birds from the area.

The intended target is usually crows or pigeons that are a nuisance in urban areas, said André Dallaire, a pathologist with the University of Montreal’s veterinary faculty in St-Hyacinthe.

Dallaire examined the birds found in the park and said the lethal dose of Avitrol was confirmed by external testing. He said the birds appeared to be in good health and died quickly.

“We always have those cases every year of birds that die of that – acute intoxication,” he said.

According to the official Avitrol website, “there is always some mortality,” when the product is used.

It also warns that it can be fatal to any invertebrate species that ingests it, not just birds.

The website cites a study conducted by researchers at the University of Ottawa that found the effect of the substance on the birds is not painful.

However, the substance has proved controversial enough to be banned by some municipalities.

The Humane Society of America, which has taken a firm stance against the use of the substance, points out that New York state banned the use of Avitrol in New York City more than a decade ago.

In 2009, Health Canada investigated after 40 grackles, a type of songbird, dropped from the sky and convulsed violently after eating grain tainted with Avitrol.

In that case, Health Canada's Pest Management Regulatory Agency found the substance wasn't used as directed and it was likely that misuse that attracted the songbirds.

Unknown who left laced-grain in park

In Montreal, it remains unclear who left the fatal grain in the park.

The City of Montreal says it wasn’t behind the incident.

Spokesperson Philippe Sabourin confirmed the city did not use chemical products to control animal populations in Jarry Park.

He refused further comment on the duck deaths until city officials have reviewed the necropsy report.

Dallaire said the substance, which comes both in a pre-coated grain and a pure form, requires a permit to obtain.

However, that restriction was only imposed recently, he said.

It's likely that whomever left the Avitrol-laced grain in the park was targeting the ducks, he said.

“In that particular case, because of the amount the ducks ingested and because of the amount of Avitrol detected in (those) birds…someone I guess wanted to get rid of those ducks for some reason," he said.

"I wouldn’t be able to prove any of that, but it’s likely what happened.”