A Wild Home on the Bones of the City

Photographs by Patricia Homonylo

Story by Sarah Gilman

On a muggy May morning with thunderstorms in the forecast, I help Gail Fraser slide a canoe onto the clear waters of Lake Ontario, then hop into the bow. We are here for a look at the Leslie Street Spit, a once lifeless pile of demolition rubble and dredged sediment that has become an improbably wild haven within Toronto, Ontario—Canada’s largest and most multicultural city. As Fraser steers us along the spit’s 5-kilometer-long shoreline, she points out broken concrete and brick peering from beneath green brows of scruffy shrubs, grasses, and trees. Beyond, joggers and cyclists move along the single cracked access road, where turtles bask in wide puddles and snakes slither across trailheads. Nearing the outlet of a small bay, we catch sight of the largest known colony of double-crested cormorants (Nannopterum auritum) in North America. Tens of thousands of birds arrive each spring from the southeastern United States and Gulf of Mexico to spend a few months feeding, breeding, and rearing young here at the end of one of the spit’s short peninsulas, just across the harbor from Toronto’s thicket of skyscrapers.

Fraser lowers her voice as we glide closer to the colony. Ranks of sinuous black birds mill aimlessly on the mud at the lake’s edge, like a bunch of people dressed in formal wear before a reception. Behind these “loafers,” as Fraser calls them, thousands of mounds of woven sticks spread across the flats toward the trees. Cormorants add material to these closely packed nests year after year. Today, each is attended by at least one incubating parent, and many are watched over by both.

To avoid startling the birds, we land out of sight behind a trapezoid of plywood, hog wire, and tarp that serves as Fraser’s blind. We cinch down our double-barreled respirators to seal out potential pathogens and the musky stink of guano. Then we crouch-walk up the bank and crawl through the spiderweb-draped tunnel to the viewing platform concealed inside the blind.

Fraser, an animal behavior researcher based at nearby York University, is tall and capable-looking—a backcountry canoe enthusiast with wavy, reddish hair and square-framed prescription sunglasses. Although she’s studied offshore oil and gas development’s impacts on seabirds off of Newfoundland and Labrador, the Leslie Street Spit’s dynamic mix of natural and industrial makes it her favorite study site, and she’s monitored the cormorant colony’s reproductive success here since 2008. Her research is part of a larger effort to balance human desires for this locally treasured landscape—also known as Tommy Thompson Park—with the needs of a native bird that is widely viewed as a pest.

Through gaps in the tarp, we peer at this season’s residents. “I think they’re very beautiful,” Fraser says, noting the cormorants’ striking turquoise eyes and their glossy breeding plumage, iridescent as an oil slick. “And I think they’re very goofy,” she adds. During courtship, mates “entwine their necks and show each other the insides of their mouths”—colored the same brilliant turquoise as their eyes. Now, several weeks after they’ve paired off, many cormorants vigorously preen themselves and their mates, flaring their 120-centimeter (four-foot) wingspans to the sun. Others flap their loose throats—called gular pouches—to cool off. A few zip in and out of the colony with twigs and lake trash to augment their nests, most of which conceal clutches of downy chicks. Prehistoric-sounding “gwho-O-O-O-o-O-o-ohrks” and grunts fill the air.

The scene is unusual for more than its abundance of birds. Often, double-crested cormorants nest in trees, or on islands and cliffs that make it harder for predators to reach them and their babies. Here, even though the spit connects to the mainland, the vast majority of nests are on the ground. That’s by design.

When cormorants began nesting in Tommy Thompson’s nascent cottonwood forests in 1990, many people saw their presence as proof of the park’s growing ecological value. But as the colony expanded, the birds stripped more and more trees of foliage and branches to build nests. They also changed the soil composition around them with acidic guano, causing trees to die and fall. If the changes continued, Toronto would struggle to meet its urban tree-cover goals. Other birds that had come to rely on Tommy Thompson’s small forest would also lose a key breeding ground and migration stopover amid the city’s sprawl.

Agencies elsewhere have often responded to impacts like these—real or perceived—by killing cormorants. On Middle Island, in Point Pelee National Park in Ontario, Parks Canada has been shooting cormorants to protect trees since 2008. On East Sand Island, at the mouth of the Columbia River on the Oregon-Washington border, the U.S. Army Corps of Engineers initiated a cormorant-shooting campaign in 2015 to reduce the number of birds eating juvenile salmon, even though dams are the primary threat to the fish. Meanwhile, under a nationwide permit, state and tribal wildlife agencies in the contiguous U.S. can kill around 120,000 cormorants per year to protect fisheries, aquaculture, property, endangered species, and more.

The Toronto and Region Conservation Authority (TRCA) that manages Tommy Thompson wanted to try something different. Starting in 2009, it hired crews to haze the cormorants out of the park’s remaining forest. Today, 15 years into the hazing, around 90 percent of the birds nest on the bare ground, up from 15 percent before the effort started. Most years, the majority of nesting cormorant pairs that Fraser monitors successfully rear young. Meanwhile, Tommy Thompson’s tree loss has largely subsided, and the list of birds using the park continues to grow. More than 330 species—including colorful warblers, flycatchers, and rails—have been spotted here.

The vibrant melee of the cormorants’ ground colony is proof that humans can make a kind of peace with this long-antagonized bird. But the colony’s ongoing evolution also suggests that true coexistence may demand something more from all of us, as this species and countless others try to adapt and thrive in our changed—and changing—world.

Tommy Thompson’s double-crested cormorants hint at the abundance that once existed across the species’ range, which includes waterbodies across much of the Lower 48 and central Canada, as well as coastlines in Mexico, Cuba, Alaska, and Canada. According to conservation biologist Linda Wires, author of The Double-Crested Cormorant: Plight of a Feathered Pariah, 19th-century observers in the Midwestern United States reported flocks so big that they darkened the whole sky, while those in the South described black ribbons of birds from horizon to horizon. One colony in Baja, Mexico, hosted 213,500 nesting pairs, equivalent to a whopping two thirds of the entire current estimated breeding population of 630,000 birds. Historical evidence of double-crested cormorants is thin around the Great Lakes, leading some to conclude that they didn’t start breeding there until after 1913, when a colony was reported at the western edge of Lake Superior. But Wires argues that Indigenous peoples’ place names and scattered records from both sides of the U.S.-Canada line suggest double-crested cormorants have occupied the region for much longer.

The species is one of about 40 in the cormorant family worldwide, all of them skilled fishers. For hundreds of years, people in China and Japan literally harnessed these abilities to fish for themselves, training cormorants from birth and looping string around their necks to keep them from swallowing the catch. And just as with other species that humans view as competitors, cormorants’ piscine appetites are the root of their persecution. European settlers, who carried prejudices against cormorants from their home countries, saw the double-crested cormorants of their adopted continent as insatiable, gluttonous, even sinful. When the so-called crow ducks began gobbling up the easy pickings inside fishermen’s nets, they were blamed for fish declines likely caused by commercial fishing fleets. For this and other reasons—“or for no reason at all,” as one natural historian put it—North America’s new human residents systematically slaughtered the species, shooting adult and young birds and destroying eggs and nests. Cormorants abandoned breeding colonies, and populations declined steeply through the late 1800s and early 1900s.

Then, starting in the 1950s, the widely-used pesticide DDT dealt another major blow. One of the chemical’s breakdown products, called DDE, found its way into fish and bioaccumulated in cormorants’ fatty tissues, thinning the shells of the eggs they laid. DDE has the same effect on many bird species, but double-crested cormorants are especially sensitive because they wrap their webbed feet around their eggs when they incubate—essentially standing on them. In one emblematic disaster in 1972, more than 95 percent of the eggs at a colony on Lake Huron had broken or vanished by the end of the breeding season. But after the U.S. and Canada banned DDT starting in the 1970s, cormorants began a stunning rebound. And it just so happened that in Ontario, a new piece of habitat was taking shape.

For years, the harbor authority for Toronto had been dumping debris into Lake Ontario to create a breakwater for ships entering from the Saint Lawrence Seaway—a series of locks connecting the Great Lakes to the Atlantic Ocean. Into the lake went the remains of Victorian brick buildings and other structures demolished to make way for new subway lines and skyscrapers, until the long, straight spine of the Leslie Street Spit rose above the water’s surface. Dredged sand and silt from the harbor became peninsulas and bays along the spit’s sheltered side, and the landform began to resemble a ragged duck foot from the air. As time passed, seeds carried by wind and birds joined seeds that rivers had carried into the lakebed sediments before they were dredged, and these sprouted weeds as well as grasses, eastern cottonwoods, and other plants that had once been common along the lakeshore before it was industrialized. 

Container-carrying trucks and trains ended up derailing the expected shipping boom, so in the 1970s, officials began considering how to develop the spit into an aquatic recreation park. Proposals were floated for marinas for 1,000 boats, soccer fields, an amusement park, an aquarium, and even a relocated airport. By that time, though, the “accidental wilderness” was drawing huge numbers of nesting waterbirds, starting with common terns and ring-billed gulls, and later black-crowned night herons, Caspian terns, and others. Birders hopped fences to view them and ultimately helped mount a successful campaign to ensure the spit, built of the city’s bones, became a nature reserve. Cormorants’ expanding presence in Tommy Thompson was just one compelling sign of their post-DDT comeback throughout the Great Lakes region. Another was a resurgence of antipathy against the birds.

There is no doubt that nesting cormorants can kill trees and alter small patches of habitat, but evidence that they harm wild fish is thin. Though researchers have conducted hundreds of studies examining diet across cormorant species in the days since settlers waged their early killing campaigns, there are only around two dozen that statistically assess the birds’ impacts on fisheries. A 2021 meta-analysis that compiled and reviewed those studies found no generalized negative effect—just isolated examples where certain cormorant species disproportionately targeted certain fish species in specific locations. In natural settings, double-crested cormorants mostly eat small, noncommercial fish. Their large numbers in the Great Lakes may actually be supported by introduced, non-native forage fish, such as alewife. And according to the TRCA, monitored coastal and nearshore fish populations along the Leslie Street Spit have not changed since the rise of the cormorant colony. 

Despite the lack of clear evidence, the smear on cormorants’ reputation persists like so much guano. In 2018, Ontario’s Ministry of Natural Resources took up a proposal supported by hunting and angling and commercial fishing groups to address the birds’ “potential” harms with a province-wide hunt. The original plan called for a nearly year-round open season—including spring when breeding takes place—during which anyone with a small game license could shoot up to 50 cormorants a day on lands where hunting is allowed. (Hunting is forbidden in Tommy Thompson Park, as it is in many urban and protected places.)

After pushback from the public and its own scientists, the ministry in 2020 confined the hunt to the fall, and reduced the bag limit to 15. For the hunt to proceed, the province also amended its Fish and Wildlife Conservation Act to classify the birds as game animals and, because most people won’t eat cormorants, to exempt them from provisions that forbid wasting game meat. The ministry also promised to monitor the hunt’s effects on Ontario’s cormorant population. But it set no specific goals. It also didn’t offer plans for monitoring whether the hunt helped fish populations, nor require hunters to report kills.

Fifty scientists, including Fraser, called out this lack of scientific rigor in an open letter, to no effect. So far, the only account of the toll is a single, self-reported small-game hunter survey, conducted every five years, which recorded 961 hunters killing 6,336 cormorants across the province in 2020. According to a ministry spokesperson, aerial counts of nests at known colonies suggest that the number of breeding birds in the province—about 126,000—had not significantly changed as of 2021, when the last one was conducted. “There is not enough hunter interest and effort to negatively impact the population,” the spokesperson wrote in an email.

A lot of hunting seasons have passed since those counts, and cormorants take several years to reach sexual maturity. A significant number of those that migrate to and from Ontario aren’t breeding and nesting yet. The number of chicks born in any given season isn’t reflected in nest counts either. Both of these things mean that declines could easily be masked or take years to show up in official numbers. For her part, Fraser believes the losses from Ontario’s hunt could be large. She and TRCA staff have put leg bands with unique numbers on a few dozen chicks among the tens of thousands that fledge at Tommy Thompson’s colony each year, in hopes of tracking their fates over time. Even those banded juveniles have turned up among hunters’ kills in the fall. “Which is amazing,” Fraser says. “Like proportionally, I was shocked. … The odds of getting a report on a band are so low to begin with.”

Because Ontario’s cormorants head south for winter, the hunt and other recent moves against cormorants in Canada—including expanded culling in Alberta and Newfoundland and Labrador—could compound with lethal management in the U.S. to chip into the gains cormorant populations have made. And every year, photos appear on Facebook forums showing Ontario hunters smiling over stacks and stacks of dead birds, which they either bury or throw away like garbage.

The morning after I join Fraser in her blind, I take a circuitous journey to the “bad side,” a small patch of forest behind Tommy Thompson’s ground colony where cormorants still manage to nest in trees despite ongoing hazing. Curtis Murley, Justin Perri, and Andrea Chreston have suited up for the occasion in hard hats, safety goggles, and respirators, as well as reflective vests or work coats despite the warm sun. The gear might be uncomfortable, but as Perri points out, it’s real good at keeping poop off your face. Indeed, the two young men already bear splatters of guano across their rakishly tilted helmets. “Don’t be surprised if a fish lands on you,” Chreston says, her hood drawn over her own helmet to protect her long, blond ponytail from the birds. “They do regurgitate.”

Perri and Murley belong to this season’s crew of field staff responsible for hazing cormorants for the TRCA in Tommy Thompson six days a week from mid-April through mid-June. Chreston, the senior project manager for the park, has been involved in the cormorant effort in various capacities since task force meetings began more than 15 years ago.

So far today, we have—simply by standing nearby—spooked a handful of cormorants from the water next to a still-forested peninsula. TRCA observes a strict no-cormorant policy there to protect a station tucked into the trees, where volunteers catch and band songbirds to see which species are using park forests. We’ve also patrolled the forest immediately behind the main cormorant ground-nesting colony. There, finding one tree with 150 cormorants roosting, Murley and Perri yelled “HEYHEYHEYHEYHEYHEY” in unison until the birds flushed en masse in a great, graceful parabola.

Putting lethal management aside “really pushed us to be creative,” Chreston explains. Early on, crews tried to get more birds to shift to the ground by manually moving tree nests. But the cormorants deconstructed them and used the materials to build nests in places they chose. The crews also provided straw as nesting materials, placed tires and stakes in grid patterns that they hoped the birds would use as foundations to build nests, and tried to attract them to new sites with cormorant decoys, without much success.

The best strategy turned out to be letting cormorants have the places in the park where they had begun ground nesting on their own, Chreston says. Crews then could use human presence and varying levels of noise—as Murley and Perri have shown me—to keep the cormorants out of the remaining forest. Because songbirds avoid nesting near cormorants, the hazing does not affect them. And monitoring has shown that other waterbirds who do nest alongside cormorants, like herons and egrets, seem to learn that the hazing isn’t targeting them and stay put. Crews also try to knock new cormorant nests out of the trees before the birds have a chance to rear young in them.

That’s next on our task list for the day. Murley and Perri shoulder bundles of yellow forestry poles, each longer than the men are tall, and we all set off down a path through shoulder-high stinging nettles. Ducking under a branch and into a startling sort of atrium, I see right away why the crew uses “bad side” as shorthand to describe the profound change that has taken place here. We stand in a cavernous space walled with denser forest and pillared here and there with partially naked trees, still leafed in tufts but mostly decorated at the branch ends with cormorant nests. A deep thatch of sticks and fallen branches covers the ground where lush understory would usually grow, along with debris—nautical rope, a plastic coat hanger, part of a gold swim cap—that the birds may have found appealing as nest material. Perhaps 300 cormorants periscope their heads at us, their tails cocked at jaunty angles, their guano pattering down like soft rain.

Most of these birds’ nests are too far along to disturb. The crew leaves those more than 10 days old to avoid harming mature eggs or chicks and will come back in the winter after migration to remove those that remain so that birds can’t use them the following year. But Murley and Perri have identified one new start in the canopy, in a spot where they recently removed a partial nest. They set about linking pole sections together, stabilizing the heavy lengthening tool as best they can against a neighboring tree and through a high crotch of branches to keep it from whipping around like a partially cooked spaghetti noodle. 

For over an hour, the two men switch off bouncing the pole’s dangling top end into the lacework of sticks 20 meters (65 feet) above our heads, encouraging each other with an occasional “You’re touching it!” or “It’s on the verge!” They knock a few pieces loose, but the nest holds fast. Some fall easily. And “sometimes it’s impossible to remove a nest with any tools because they wrap it into the trunk with twine,” Murley says, with obvious respect for the cormorants’ skill. “I’ve never seen a few sticks be this strong before,” adds Perri. “They’re definitely good architects.”

The crew might have had more luck had they used a giant slingshot called a Big Shot to fire a rope through the treetops that would allow them to more effectively guide the pole end. But Chreston says the Big Shot was needed elsewhere—a new wrinkle in the ecological transformation of Tommy Thompson. Some of the colony’s cormorants, it turns out, are on the move.

Back in 2023, Gail Fraser had a surreal experience in Tommy Thompson Park. It was a summer night, and she was working with TRCA staff to put leg bands on cormorant chicks in the ground colony. Members of the crew slipped quietly through the darkness among thousands of hunkered black birds while party boats with lights and thumping music and crowds of human revelers glided past beneath the city’s glittering skyscrapers. And then Fraser made a discovery that compounded the strangeness: At her feet lay a bird with its chest torn open, still alive. “The breast meat was fully intact, so we probably just disrupted something,” she remembers. Beyond it, toward the back of the colony, lay dozens more dead birds.  

Fraser and her PhD student, artist Cole Swanson, set up camera traps and found the culprits: Coyotes were taking cormorants near the forest’s edge. Then a pair of raccoons moved into Fraser’s blind. That winter, she crunched the numbers for the 80 or so nests she had been monitoring and learned that the proportion of young to successfully fledge had fallen from over 90 percent to 40 percent. The predators that were slowly infiltrating the park had finally made it to the center of the cormorant colony.

When waterbirds first arrived on the Leslie Street Spit decades ago, the relatively barren landform functioned like an island. Gulls and terns nested right on the rocky shore, mostly free of disturbance. But as the young trees grew into forest and restoration projects in Tommy Thompson Park helped speed nature’s advance, the habitat attracted mink, otters, foxes, owls, coyotes, and other animals. In other words, the spit is now functioning more like a diverse part of the mainland it is physically connected with. There’s “a lot of really positive wildlife sightings … to indicate we’re going in the right direction,” Chreston says. “Wildlife communities are returning to the Toronto waterfront.”

Those communities are also still very much in flux on this dynamic swatch of land. Predators likely caused ring billed gulls to all but abandon their breeding colony in Tommy Thompson—estimated at its peak to number around 75,000 breeding pairs. And since 2018, the number of nests in Tommy Thompson’s cormorant colony has fallen from a high of nearly 15,000 to stabilize around 9,000 to 11,000.  While flooding from high lake levels in 2019 likely contributed to the change, some cormorants may have simply left to escape the escalating threat of predation. Indeed, in 2022, new nests were reported across the water from Tommy Thompson, in Toronto Island Park.

The colony there turned out to contain more than 1,600 nests. The city didn’t want cormorants damaging the trees in Toronto Island’s wetlands, so it contracted TRCA to try to keep them out entirely. The agency ended up putting more than a dozen staff on the ground in the park in rotating crews from dawn until dusk, seven days a week, all season long. Using the same deterrence protocols Tommy Thompson crews use, they brought the number of nests down to 900. But in 2024, a pair of bald eagles—the first to nest in the city in recorded history—alit in the same Toronto Island wetland that the cormorants had chosen. Managers instituted a 100-meter buffer zone around the eagles to avoid disturbing them. Though crews prevented cormorants from nesting in the rest of the wetland, the intelligent birds managed to build more than 1,200 nests within the protection of the buffer zone.

Chreston says it’s important to recognize that the ground colony at Tommy Thompson is still thriving despite predation. Its great numbers offer certain protections, and after Fraser sealed the raccoons out of her blind to keep them from denning, productivity at the nests she monitors climbed back to nearly 90 percent in 2024. But TRCA is working to increase the colony’s long-term appeal anyway, to keep more birds from shifting to Toronto Island. For the 2024 breeding season, the agency borrowed an idea from Ontario’s Presqu’ile Provincial Park, which switched from lethal to nonlethal cormorant management in 2007, and built a latticed wooden structure called the “cormdominium.” When I visit, hundreds of birds are nesting and roosting on the multilevel structure, surrounded by a low fence to keep out some predators.  

TRCA has doubled the cormdominium’s 330-square-meter (395-square-yard) footprint for 2025, even as it continues to send round-the-clock crews out to deter the birds from nesting in Toronto Island Park. “Cormorant management is adaptive management,” Chreston acknowledges, laughing.

To people who favor killing cormorants, going to such lengths might seem like an overwrought waste of time, effort, and money. But programs like Tommy Thompson’s are only small concessions to the wild beings with whom people share their home places. After all, the modifications cormorants make to their environment are minuscule compared to the lively sprawl of a city and all the forests and fields and soil that it replaces with concrete and glass and asphalt and wood and lawn. This urban mudflat and its ruckus of gleaming, obsidian birds has its own lessons to offer about wildness and all the ways it finds to persist in a world our kind has so deeply altered. Perhaps someday more of us will step beyond the fragile détente of “coexistence” and allow other beings to decide on their own behalf, in their own best interests, how and where they make their lives alongside us.