It’s safe to say that double-crested cormorants are causing a stink — in more ways than one — on the Toronto islands.
They poop everywhere, which is driving people away. And since that poop is acidic, it’s also bleaching and destroying the trees they nest in.
“Rome is burning, and the bureaucrats are fiddling. Each year it gets worse and worse, with more carnage and death to the trees,” said Warren Hoselton, who worked on the islands as the park supervisor for over two decades.
“We manage Canada geese, we manage beavers — and we’re letting these guys have at it.”
Around 18,000 double-crested cormorants have made Hanlan’s Point their home, close to a public docking area. The population has tripled in size over the last year, according to the Toronto and Region Conservation Authority (TRCA).
Those who live and spend time on the islands want them relocated. But that’s not as easy as it sounds.
The bird poop — called guano — is responsible for turning what was a tree-filled, green shore line into something you might see in a dystopian film.
And in this one, the cormorants are the villains.
“It’s hard not to describe it as an apocalyptic scene for a forest,” said Gordon Ballantyne, the general manager at the Toronto Island Marina.
Ballantyne says he used to see up to 140 boats tied up along the public docking at Hanlan’s Point on a long weekend. But that has significantly dropped, thanks to the cormorants doing their business.
“People go to bed, they wake up and their boat is covered in, uh, in what the cormorants are dropping,” said Ballantyne.
It’s believed that the cormorants came from another colony, which lives just a short flap of the wings away at Tommy Thompson Park on Toronto’s mainland, just east of the islands.
While the TRCA can’t be sure, the arrival of the Toronto islands contingent in 2022 coincided with a population drop at Tommy Thompson Park.
The group says some of the birds may have relocated because on the mainland, there are more predators who consider a cormorant nest of chicks a tasty midnight meal.
“The raccoons, when they come into the colony, they don’t grab a bird and then take it out of the nesting area. They just sit at the nest and eat the chick,” said Gail Fraser, an avian ecologist at York University who monitors the colony at Tommy Thompson Park.
That stress, she says, could be why cormorants are moving away.
In some places across Canada, including in Ontario, cormorants can be culled. But because this flock resides in Toronto city limits, a bylaw protects them from being shot.
The TRCA, working on behalf of the City of Toronto, has been managing the roughly 30,000 birds at Tommy Thompson Park.
It’s willing to let nature decide the size of the colony, but what it doesn’t want is cormorants nesting in trees, because their poop is so destructive. Since the birds don’t mind nesting on the ground, the TRCA has to convince them to leave their branches and do so.
And that takes a lot of convincing. During its seven-week breeding season in the spring, staff spend hours yelling up at the cormorants, trying to get them to leave their nests. When that no longer works, they use pyrotechnics to scare the birds away.
“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 are pooping and regurgitating fish all over you, it is a mess,” said Andrea Chreston, a senior project manager with the TRCA.
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Then, they poke the nests out of the trees, which are 80 to 100 feet high. But that isn’t always a permanent fix.
“So it’s not only physically demanding, but it is emotionally demoralizing,” said Chreston.
“You’re like, ‘Yes, I’ve removed this many nests on any given day.’ And then you come back the next day and the birds have rebuilt their nests. So you’re constantly having to redo the very hard work.”
But it has been successful. According to the TRCA, just 15 per cent of the colony at Tommy Thompson Park was nesting on the ground in 2008. By 2024, that was up to 90 per cent.
Not everyone sees the cormorant as a feathered villain. For one, they are native to the area, not invasive.
Chreston says that though they have a reputation for devouring fish, according to research done in the U.S. in 2003, the birds don’t actually hurt the overall stocks.
And Fraser says it’s important to recognize that while the cormorants have done a number on trees in the area, they aren’t the harbingers of death they appear to be.
Yes, their poop is responsible for destroying forests. But Fraser says it’s not habitat loss. It’s habitat transformation.
“Losing habitat is when you build a parking lot and build a Home Depot, right? That’s losing habitat,” said Fraser.
“Where we’re standing was forest at one point. And now, ring-billed gulls can nest on the ground here because it’s no longer a forest. So it just creates habitat for other species.”
Chreston says the TRCA has been applying some of the same tactics on the Toronto islands as it has at Tommy Thompson Park.
But on the islands, the entire colony nests in trees, and since there’s no space for them to nest on the ground without first killing trees, all the TRCA can do is try to get them to leave. During the breeding season, Chreston and her team work from morning to evening, every day, trying to scare the birds off.
The TRCA is trying to lure the cormorants to Tommy Thompson Park with what they call cormorant condos — basically, a wall-less wooden structure equipped with predator protection, to try to keep hungry raccoons away.
TRCA field staff have been knocking down cormorant nests on the islands, too. And Chreston says for a few years, the population was dropping. But then in 2024, eagles nested in the midst of the cormorant colony, making it a protected zone.
Chreston and her staff could no longer harass cormorants or knock down their nests in the area directly around the eagles, and the cormorants flocked to it. The population jumped back up.
Fraser supports the work the TRCA is doing. She says it’s more humane than many other places across Canada that have chosen to kill the birds.
But she has another idea. She suggests an entirely new place for the cormorants to rest: a bird barge.
About 30 years ago, the City of Hamilton built three islands to solve its own bird problem, which cost $2.4 million, and proved to be effective.
The TRCA is “in the early stages of investigating” a floating habitat, according to Chreston. She says they are constantly adapting their management plan, but it will take years before they can move all the cormorants.
“Because our landscapes are so altered by human practices, there’s limited nature left,” said Chreston.
That’s why she wants them to move to Tommy Thompson Park, “where there’s ample habitat and good habitat for them. Where they’re not going to be further decreasing overall biodiversity.”
