Five of six samples taken from dead pigeons found in downtown Charlottetown have come back positive for a substance called Avitrol, described by its manufacturer as a flock deterrent.

The pigeons who eat Avitrol exhibit unusual behaviour, including seizures, and scare away the rest of the birds. But on the company's website, it also says that the substance can cause mortality.

Dr. Maria Forzan, of the Canadian Wildlife Health Cooperative, performed the necropsies on the pigeons at the Atlantic Veterinary College in Charlottetown and sent the samples for testing at a toxicology lab at the University of Guelph.

She wants the pest control applicators and the public to know the effects of Avitrol.

"Trying to explain to them that, in fact, it is quite possible that a lot of the pigeons will die from Avitrol poisoning which is actually something that came as a surprise to us," explained Forzan.

Dead pigeons found throughout downtown

​The pigeons were found in downtown Charlottetown, ranging from Victoria Row to Victoria Park, and Forzan says it's possible they were all feeding at the same location.

Forzan went back to the labelling information for Avitrol to find out more about what the company said about bird mortality from the product.

Dr. Maria Forzan wants Islanders to understand the way that Avitrol works on birds such as pigeons. (Nancy Russell/CBC)

"We were under the impression from the older literature and from what the company was putting out, years ago when we first looked at this, about how pigeons would show abnormal behaviour and frighten the other pigeons away but only a few of them will die."

That's no longer the case she said — "If they show clinical signs, they are likely to die."

'There's going to be some suffering'

​Forzan is thinking about writing a letter to the editor to the Canadian Veterinary Journal to spread the word about the pigeon deaths from Avitrol, but admits it's up to the public to decide if this is an appropriate way to control the pigeons.

"If people are upset about pigeons defacing buildings or cars, then something is going to be done, and whether we see it or not, people need to be aware that any time you kill an animal that you consider a pest, there's going to be some suffering and some unpleasant sights," said Forzan.

AVC wildlife technician Fiep de Bie with one of the "very sick" pigeons that were found around downtown Charlottetown. (Nancy Russell/CBC)

On P.E.I., only pest control professionals are allowed to use Avitrol.

Eleven companies are currently licensed across the Island and the licences are issued annually, expiring at the end of the calendar year.

A spokesperson for the P.E.I. government says staff in the Department of Communities, Land and Environment know who is administering the Avitrol in Charlottetown, and they have had conversations with that person about safe use of the substance.

Some of the pigeons recovered but others died despite the care at the AVC> (Nancy Russell/CBC)

Samples from three more dead pigeons have been sent to Guelph for testing, but no more sick birds have been reported.

"I'm kind of guessing that whoever was using Avitrol has realized that it's probably not the best public relations results and maybe they've realized what it's doing to the pigeons and they've stopped, or basically the problem has resolved itself, maybe the pigeons are no longer there," observed Forzan.

CBC called and emailed Avitrol for comment, but did not receive any response.