Netting, noise cannons keep gulls off TTC facility

After a Toronto Transit Commission facility was swarmed by seagulls this spring, noise cannons and netting have successfully kept the birds from nesting on its green roof, a spokesperson said.

In March, the TTC installed the deterrence measures at Leslie Barns, which houses streetcars near Leslie Street and Lake Shore Boulevard E., due to health and safety concerns caused by the large amount of feces the birds — specifically ring-billed gulls — were unleashing on the ground below. 

Stuart Green, a spokesperson for the TTC, said the downpour of droppings was so bad that some staff had to be equipped with umbrellas to make it to their cars. At the time, the TTC said the excrement created slip and fall risks and could increase the risk of avian flu transmission. 

As a result, netting, sound cannons and inflatable scarecrows were installed until June, according to Green.

"The netting kept them off the roof, the cannons kept them off the netting. So it was really a combination of things that worked," Green said in a recent interview with CBC Toronto. 

"The inflatable scarecrow wacky arm thing, we don't believe that had too much of an impact at all. In fact, the seagulls were probably laughing at it."

Green said the sound cannons didn't need to be used as often as the TTC expected. He said they were prepared to fire them off 3,000 to 4,000 times over three months, but only had to use them about 500 times.

Gulls will remember being scared away

The mitigation measures were only necessary in the spring because that's the species' nesting season, according to Gail Fraser, a professor in the faculty of environmental and urban change at York University. She said it's unlikely the birds will return to try and nest on the roof next spring because they will remember the failed previous attempts, which could lead them to nest on other nearby rooftops. 

"It wasn't surprising to me that when a football-sized green roof showed up next to the Leslie Street spit that the gulls would start using it," she said. The spit is the land that stretches into Lake Ontario and holds Tommy Thompson Park. 

"I had hoped that there would be a more positive outcome for the gulls in that situation. But I understand there's challenges." 

Fraser said she hoped there could be a way to allow them to nest in lower numbers, so there wouldn't be as many conflicts between the gulls and humans. 

'I've never seen that many birds on a roof'

Dave Moore, a waterbird biologist with Environment and Climate Change Canada, worked with the TTC to help address the gull issue. 

"I've never seen that many birds on a roof before," he said.

He said when figuring out how to stop the birds from landing on a roof, they usually work through a progression starting with the least invasive methods. 

Usually, he said, that starts with physically deterring them from being able to nest on the roof. Scaring them away, with something like a noise cannon, comes next, which is key because it's harder to get them off if they've already established a nest.

Moore said ring-billed gulls typically nest on islands throughout the Great Lakes region and in an urban setting, green roofs are sort of like islands, because they keep them away from predators.

He said a recent survey shows the number of ring-billed gulls nesting in natural areas is declining but their presence is increasing in cities. 

"We're trying to understand why we're getting this shift in habitat from these natural areas where the conflicts don't occur into these urban areas where they do," he said.