The Sunday Magazine23:07Sunday Documentary: The Cormorant Enigma
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 scares people away. And since that poop is acidic, it also bleaches and destroys the trees in which they nest.
“Rome is burning and the bureaucrats are fiddling. Every year the situation gets worse and worse, with more killings and dead trees,” said Warren Hoselton, who worked on the islands as a park supervisor for more than two decades.
“We handle the Canada geese, we handle the beavers, and we let these guys take care of that.”
Around 18,000 double-crested cormorants have made their home at Hanlan’s Point, near a public docking area. The population has tripled over the past 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 seems.
What’s wrong with these birds?
Bird poop, called guano, is responsible for turning what was a full of trees, greon the coast in something you might see in a dystopian movie.
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, general manager of the Toronto Island Marina.
Ballantyne says he used to see up to 140 boats tied up at the Hanlan’s Point public dock on a long weekend. But that number has decreased significantly thanks to the cormorants doing their job.
“People go to bed, wake up and their boat is covered in what cormorants drop,” Ballantyne said.
What is your origin story?
The cormorants are believed to come from another colony, living just a short flap of the wings away in Tommy Thompson Park on the Toronto 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 in Tommy Thompson Park.
The group says some of the birds may have relocated because more predators on the continent consider a nest of cormorant chicks a tasty midnight meal.
“Raccoons, when they come into the colony, don’t grab a bird and then take it out of the nesting area. They just sit on 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, he says, could be the reason the cormorants are moving away.
What can be done?
In some places in Canada, including Ontario, cormorants can be euthanized. But because this flock resides in the Toronto city limits, a bylaw protects them from being shot.
The TRCA, working on behalf of the City of Toronto, has been managing approximately 30,000 birds at Tommy Thompson Park.
He is willing to let nature decide the size of the colony, but what he does not want is for cormorants to nest in trees, because their excrement is very 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 requires a lot of convincing. During their seven-week breeding season in the spring, staff spend hours yelling at the cormorants, trying to get them to abandon their nests. When that no longer works, they use pyrotechnics to scare away the birds.
“When you’re in the middle of the season and the weather is bad and it’s raining and… you’re standing under the cormorants and they poop and regurgitate fish on top of you, it’s a disaster,” said Andrea Chreston, TRCA senior project manager.
Conservation groups near Big Rideau Lake say hunting the area’s native shorebirds is unethical and unnecessary. But starting Sept. 15, hunters can kill up to 15 a day. CBC’s Stu Mills reports.
They then remove the nests from the trees, which are 80 to 100 feet high. But that’s not always a permanent solution.
“So it’s not only physically demanding, but it’s also emotionally demoralizing,” Chreston said.
“You say, ‘Yes, I’ve removed so many nests on a 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 hardest work.”
But it has been successful. According to the TRCA, in 2008 only 15 percent of the colony at Tommy Thompson Park nested on the ground. In 2024, that figure rose to 90 percent.
Why protect cormorants?
Not everyone sees the cormorant as a feathered villain. On the one hand, they are native to the area, not invasive.
Chreston says that although they are famous for devouring fish, according to research conducted in the USA in 2003The birds don’t actually harm the overall populations.
And Fraser says it’s important to recognize that while cormorants have caused extensive damage to trees in the area, they are not the harbingers of death they appear to be.
Yes, their poop is responsible for the destruction of forests. But Fraser says it’s not about habitat loss. It is the transformation of the habitat.
“Habitat loss happens when you build a parking lot and a Home Depot, right? That’s losing habitat,” Fraser said.
“At one point where we are was a forest. And now, ring-billed gulls can nest on the ground here because it’s not a forest anymore. So it just creates habitat for other species.”
Possible solutions
Chreston says the TRCA has been applying some of the same tactics on the Toronto Islands as it did at Tommy Thompson Park.
But on the islands, the entire colony nests in trees, and since there is no room for them to nest on the ground without first killing them, all the TRCA can do is try to get them to leave. During the breeding season, Chreston and his team work from morning to night, every day, trying to scare away the birds.
The TRCA is trying to attract cormorants to Tommy Thompson Park with what they call cormorant condos: basically a wooden structure without walls equipped with predator protection, to try to keep the hungry raccoons out.
TRCA field staff have also been taking down cormorant nests on the islands. And Chreston says for a few years the population was declining. But then, in 2024, the eagles nested in the middle of the cormorant colony, turning it into a protected area.
Chreston and his staff could no longer harass the cormorants or knock down their nests in the area directly around the eagles, and the cormorants flocked. The population increased again.
Fraser supports the work the TRCA is doing. She says it’s more humane than many other places in Canada that have chosen to kill birds.
But she 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 own bird problem, which cost $2.4 million and proved effective.
The TRCA is “in the early stages of research” into a floating habitat, according to Chreston. She says they are constantly adapting their management plan, but it will be years before they can relocate all the cormorants.
“Because our landscapes are so altered by human practices, there remains limited nature,” Chreston said.
That’s why he wants them to move to Tommy Thompson Park, “where there is ample and good habitat for them. Where they are not going to further diminish general biodiversity.”
