Cormorants and their acidic feces are causing a stink on the Toronto Islands. What can be done?

It’s safe to say that the double-crested cormorants on the Toronto Islands are causing a stink in more ways than one.

They litter everywhere, which is driving people away. And because that poop is acidic, it’s also bleaching and destroying the trees in which they nest.

Warren Hoselton, who worked as a park supervisor on the islands for more than two decades, said, “Rome is burning, and bureaucrats are negligent. Every year it gets worse and worse, with more carnage and death of trees.”

“We manage Canada geese, we manage beavers – and we’re letting these guys do it.”

About 18,000 double-crested cormorants have made Hanlon Point, close to the public docking area, their home. According to the Toronto and Region Conservation Authority (TRCA), the population size has tripled over the past year.

People who live and spend time on the islands want them relocated. But it is not as easy as it seems.

What’s so bad about these birds?

Bird feces – called guano – is responsible for overturning what was full of trees, greThe N shore lines up into something you might see in a dystopian movie.

And cormorants are the villains in this one.

“It’s hard not to describe it as a jungle apocalyptic scene,” said Gordon Ballantyne, general manager of Toronto Island Marina.

Ballantyne says he saw up to 140 boats moored along the public dock at Hanlon’s Point over the long weekend. But due to cormorants doing their business it has declined significantly.

“People go to bed, wake up, and their boat gets covered in what the cormorants are dropping,” Ballantine said.

What is their origin story?

It is believed that the cormorants came from another colony that lives just east of the islands, a short distance from Tommy Thompson Park on mainland Toronto.

Although the TRCA may not be definitive, the arrival of the Toronto Islanders in 2022 coincides with a decline in population at Tommy Thompson Park.

The group says some birds may have relocated because on the mainland, there are more predators that consider cormorant nests of chicks a tasty midnight meal.

“When raccoons come to a colony, they don’t catch a bird and then take it out of the nesting area. They just sit in the nest and eat the chick,” said Gail Fraser, an avian ecologist at York University who monitors the colony at Tommy Thompson Park.

She says that due to this stress the cormorants are moving away.

What can be done?

In some locations across Canada, including Ontario, The cormorant can be exterminatedBut because the herd lives within Toronto city limits, a bylaw protects them from being shot,

TRCA, working on behalf of the City of Toronto, is managing approximately 30,000 birds at Tommy Thompson Park.

He’s willing to let nature determine colony size, but he doesn’t want cormorants to nest in trees because their feces are so destructive. Since the birds don’t mind nesting on the ground, TRCA will have to convince them to leave their branches and do so.

And it requires a lot of convincing. During the seven-week breeding season in the spring, staff spend hours yelling at the cormorants, trying to get them to leave their nests. When that doesn’t work, they use pyrotechnics to scare away the birds.

“When you’re in the middle of the season and the weather is bad, it’s raining and … you’re standing under the cormorants and they’re digging and spitting out fish all around you, it’s a mess,” said Andrea Chastain, a senior project manager for TRCA.

Then, they pluck nests from trees 80 to 100 feet high. But this is not always a permanent solution.

“So it’s not only physically difficult, but it’s emotionally discouraging,” Kristen said.

“You’re saying, ‘Yes, I’ve removed so many nests in any given day.’ And then you come back the next day and the birds have rebuilt their nests. So you’re constantly having to work hard again.”

But it has been successful. According to the TRCA, in 2008 only 15 percent of the colony at Tommy Thompson Park was nesting on the ground. By 2024, it was up to 90 percent.

Why protect the cormorant?

Not everyone sees the cormorant as a winged villain. For one, they are native to the area, not invasive.

Kristen says that although they are known to eat fish, According to research conducted in America in 2003Birds do not actually harm the overall stock.

And Fraser says it’s important to recognize that although cormorants have attacked trees in the area in large numbers, they are not the harbingers of death they seem to be.

Yes, their feces are responsible for destroying forests. But Fraser says it’s not habitat loss. This is a change of residence.

“Losing habitat means when you build parking lots and build Home Depot, right? That’s losing habitat,” Fraser said.

“Where we are standing, there was once forest. And now, ring-billed gulls can nest on the ground here because it is no longer forest. So it just creates habitat for other species.”

possible solution

Kristen says the TRCA is implementing some of the same strategies on the Toronto Islands as it did at Tommy Thompson Park.

But on islands, entire colonies nest in trees, and since there is no room for them to nest on the ground without killing the trees, the TRCA can only try to drive them away. During breeding season, Chastain and his team try to scare the birds away from dawn to dusk every day.

TRCA is trying to lure cormorants to Tommy Thompson Park with what they call a cormorant condo – basically, a wall-less wooden structure equipped with predator protection to try to keep out hungry raccoons.

TRCA field staff are also destroying cormorant nests on the islands. And Kristen says the population had been declining for a few years. But then in 2024, eagles nested in the middle of the cormorant colony, making it a protected area.

Kristen and his staff could no longer disturb the cormorants or demolish their nests in the direct vicinity of the eagle, and the cormorants continued to flock to it. The population came back up again.

Fraser supports the work being done by TRCA. She says it’s more humane than many other places in Canada that have opted to kill the birds.

But he has another idea. She suggests a completely new place for cormorants to rest: a bird barge.

About 30 years ago, the city of Hamilton built three islands to solve its bird problem, costing $2.4 million, and it proved effective.

According to Kristen, TRCA is “in the early stages of investigating” a floating residence. She says they are continually adapting their management plan, but it will take several years to relocate all the cormorants.

“Because our landscapes have been so altered by human practices, there is limited nature left,” Kristen said.

So she wants them to move to Tommy Thompson Park, “where there’s enough habitat and good habitat for them. Where they’re not going to further reduce the overall biodiversity.”