They're Toronto Islands' newest visitors, but residents hope cormorants don't stay long

·5 min read
A double-crested cormorant is seen flying past the CN tower at the Leslie Street Spit in Tommy Thompson Park. (Laura Pedersen/CBC - image credit)
A double-crested cormorant is seen flying past the CN tower at the Leslie Street Spit in Tommy Thompson Park. (Laura Pedersen/CBC - image credit)

Hanlan's Point may be a popular destination for Torontonians in the summer, but the city and conservation officials say they're working to deter some unwanted visitors — a population of double-crested cormorants — from nesting in an environmentally sensitive area nearby.

The Toronto and Region Conservation Authority (TRCA) said it got word in May that the birds began appearing near Blockhouse Bay and Long Pond near the Hanlan's Point ferry deck at the west end of the Toronto Islands.

"There was a large increase in cormorants at the very beginning of June. And so we took immediate action to develop a sort of short-term mitigation strategy," said Andrea Chreston, the TRCA's project manager for Tommy Thompson Park.

Island residents worry about the damage the birds cause to trees. They're also not fond of the distinct odour from the cormorants' fish-based diet and their excrement. The TRCA says it's working to prevent them from nesting and expanding their footprint. But some experts say given the proximity to Tommy Thompson Park on the Leslie Street Spit, their arrival on the islands doesn't come as a surprise.

Back from near extinction

Cormorants are a native species that was in decline in the 1800s due to hunting and came close to local extinction in the 1970s and 1980s due to the use of DDT insecticide. The largest breeding colony of double-crested cormorants in North America is now at Tommy Thompson Park. Last year, there was an estimated population of 12,000 birds.

The TRCA manages the colony and works to contain the area where they nest because their acidic excrement can damage trees.

Evan Mitsui/CBC
Evan Mitsui/CBC

"The excrement sort of rains down and it changes the soil chemistry. So the nutrients are no longer sort of readily available in the soil that the tree needs to absorb," Chreston said. "And so over time, the health of the tree declines."

But their droppings aren't the only problem. Chreston says the cormorants can strip the trees of their leaves by repeatedly nesting in them over a period of years.

She says the TRCA is also trying to set up ground nests to encourage the birds to stay away from the trees.

Laura Pedersen/CBC
Laura Pedersen/CBC

She says when they learned the birds began nesting on Toronto Island, they moved in quickly.

"We removed immature nests during June to the point where we were no longer seeing cormorants attempting to build new nests," said Chreston.

As it's now the end of breeding season, Chreston says conservation workers will return in a few months when the birds fly south for winter and remove all nest material so when the cormorants come back next spring, it'll be empty.

Laura Pedersen/CBC
Laura Pedersen/CBC

"We want to encourage cormorants that have nested at the Toronto Islands to come and nest on the ground at Tommy Thompson Park."

Resident views

Some residents on the Toronto Islands are not yet sure what to make of the birds.

"We have people that really care about the environment and some of them are not so concerned, because they're native [species]. Others are really concerned that they're destroying the environment," Tony Farebrother told CBC News, pointing to the damaged trees near Blockhouse Bay.

Laura Pedersen/CBC
Laura Pedersen/CBC

Farebrother,  who is the chair of the Toronto Island Community Association, says it's the first time in his 26 years on the island he's seen them nest there. Though the area where they're nesting is a few kilometres away from residential homes, he says he's been receiving complaint letters.

"The fact that they're here is less concerning — because it's quite far from us — the concern will be will they keep spreading and will they discourage other animals, and destroy trees."

Other Island residents's views are more clear.

Laura Pedersen/CBC
Laura Pedersen/CBC

"This is certainly a new addition, but not a welcome one," said Gordon Ballantyne, general manager of the Toronto Island Marina. He says residents started spotting them in April.

Ballantyne says their distinct fishy smell is the most noticeable sign of their arrival, but that's not all.

"They're a nuisance bird in as much as they kill the trees they nest in. They come in great numbers. They swarm the area in terms of killing the fish population to some extent because that's what they're eating," he said.

Ballantyne says himself and other residents worry about whether efforts to deter the birds from nesting on the Islands will work.

"[The TRCA] say they managed to stabilize the population so it's not growing anymore. It feels as though they're still expanding in the immediate area."

Expert advocates 'tolerance and long-term planning'

It's unclear why the birds ended up nesting near Hanlan's Point.

Gail Fraser, a cormorant expert, speculates it might be due to the proximity of the colony on the spit to the Islands, the remote nature of the area they've settled in, or that they've followed another species to the spot.

"It's surprising it has taken this long for cormorants to show up on the Toronto Islands," said Fraser, who is a professor in the faculty of environment and urban change at York University.

Laura Pedersen/CBC
Laura Pedersen/CBC

Fraser says it'll take a lot of time and effort to keep the birds from returning,  especially now that they've already nested there.

"I think it's going to be several years of getting there early and really scaring them off. Because  ... right when they arrive that's when they're skittish, that's the time to really be scaring them away."

Evan Mitsui/CBC
Evan Mitsui/CBC

Fraser says the public might not be inclined to tolerate the cormorants, but she adds it's important to note they're a native species that has recovered from near extinction.

"I'd like to encourage some tolerance and long-term planning."

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