​A pest control contractor hired by Halifax has been using poison to control the pigeon population at the Keshen Goodman Public Library.

CBC News uncovered the information when the city's pest control contract came up for renewal. The new tender for services in Halifax includes a mention of "an Avitrol program" at the library.

Avitrol is described by its manufacturer as a flock deterrent. It's designed to look like corn kernels and left out for birds to eat.

​Once it's consumed, Avitrol affects the birds' central nervous system and causes convulsions that can last more than four hours. The prolonged, uncontrolled flapping is meant to scare other birds away.

The company's website states there is no way to effectively use Avitrol without some birds dying from the product.

Hope Swinimer, founder of Hope for Wildlife, says poisoned pigeons are being brought to her shelter. (CBC)

Hope Swinimer, founder of Hope for Wildlife, says she's seen a number of poisoned birds brought to her shelter.

"It looks like they are struggling, just like mini seizures," she said. "They look really confused and there's sometimes vomiting too."

​Avitrol is currently banned in New York City, San Francisco, the United Kingdom and Red Deer, Alta.

Visitors to the Keshen Goodman Library were surprised to hear the poison has been used to control birds in the area.

"I think placing poison for that is not a good idea," said Brenda Gionet.

"Sometimes my kids fall down and they put their hands on ground," said Herman Bhuller.

Poison may not be effective

"If there's poison on the ground and if they swallow it, I think that would be dangerous."

​The poison may not even be very effective. Many wildlife experts said new birds often move into the area once the previous birds are killed or scared off.

"If you revisit the spot, six months down the road, you're going to see the exact same problem," said Swinimer.

After CBC News contacted the city with questions about Avitrol, officials said the poison would no longer be specifically mentioned in the next tender for pest control, up for renewal this year.

However, there is no ban preventing Halifax's contractor or other pest control companies from continuing to use Avitrol on public or private property.