As a late-January gale bears down on Bermuda, Jeremy Madeiros stares anxiously at his computer. A livestream shows hurricane-force winds and waves battering a tiny limestone island. The rock looks uninhabited, but Madeiros knows better. Dozens of critically endangered Cahows—some of the rarest seabirds on Earth—are nesting there in subterranean burrows. If the island floods, their fragile eggs could wash out to sea. That would be a setback for the birds, whose global population only recently surpassed 350. It would also be a headache for Madeiros, who’s responsible for keeping them alive.
Madeiros is the principal scientist for terrestrial conservation in Bermuda, the only place in the world where Cahows nest. That makes him the caretaker for the entire species, a job that’s equal parts ornithologist, helicopter parent, and stuntman. And Cahows, also known as Bermuda Petrels, need all the help they can get. The docile, ground-nesting creatures have flirted with extinction for centuries. They’ve been devoured by rats, cats, dogs, hogs, and humans; assailed by tropicbirds; ravaged by DDT; and most recently menaced by climate change as hurricanes have grown stronger and sea levels have risen.
The petrels’ keeper has adopted extreme measures to help them, breaking with the hands-off style of his forebear and decades of Bermuda tradition. Madeiros has been accused of meddling too much, taking risks that might extinguish the species for good. But he believes that, on a warming planet, conservationists are running out of options that don’t involve an aggressive, hands-on approach.
A week after the storm, Madeiros welcomed me aboard the Cahow 2, a 17-foot Boston Whaler. The 62-year-old sported his de facto uniform: slip-on leather shoes, tan work pants, and the official blue windbreaker of the Bermuda Department of Environment and Natural Resources. His gray hair was tucked under a baseball cap. It shaded his deeply tanned face, which wore a goatee and a slightly impish smile.
We motored to Castle Harbor, a bay in the northeast corner of the Bermuda archipelago fringed with small, uninhabited islands; six are home to breeding Cahows. Madeiros pulled up to a chunk of weather-beaten limestone called Long Rock. About an acre in size, it was barren apart from a few hardy tangles of buttonwood and sea oxeye. Water had hollowed it out from below, collapsing part of the surface and creating a striking turquoise lagoon. As he disembarked, Madeiros warned me to be careful. Erosion had whetted sharp pinnacles along the island’s perimeter. Slipping here, he said, would feel “like falling on broken glass.”
Madeiros knows this from experience. In a little more than two decades on the job, he’s endured plenty of injuries and close calls. Jagged rocks have ice-picked him in the knee and sliced open his hand to the wrist. He was nearly hit by lightning while watching Cahow chicks exercise at night: The bolt struck a nearby tree, splitting it in half. A rogue wave once tossed his boat high in the air. It came crashing down, the stern impaled on a limestone spike.
So I stepped gingerly over the gunwale, then followed Madeiros up a short slope. He knelt beside what appeared to be a concrete Frisbee. This, he explained, was the lid to an artificial burrow. He rummaged in his backpack for supplies—cotton bags, a spring scale, and a flashlight—and tugged a spiral-bound pad from his breast pocket. Then he described his nest-checking routine. First he removes the lid. He pulls out whichever parent is on the nest, checks the identification band on its leg, and bags and weighs it. He does the same thing with the egg, then returns it to the dark nesting chamber. He props a flashlight against the shell until its contents glow and looks for signs of life: blood vessels, a stirring embryo.
I felt a twinge of excitement. Few humans get to see a Cahow up close. The birds are pelagic, spending most of their lives on the open ocean. They drink seawater and expel the salt from their nostrils. Sometimes they sleep on the wing. Every fall they arrive in Castle Harbor for nest-building and courtship on the same half-dozen rocks and islands where they fledged, then head back out to sea. In January they return to lay eggs. Sternly worded signs warn boaters away from the colonies, which are off-limits to the public. When Madeiros invited me to join him, I was thrilled; now we had finally arrived. Madeiros heaved the lid and stared into the burrow. “Ahhh, no,” he said, sighing. “This was what I was afraid of.” He pulled out a clump of sodden grass, then moved away so I could see, too. The chamber was empty. The storm had washed the egg out to sea.
Before humans arrived, birds ruled Bermuda. As many as a million Cahows shared the night skies with Audubon’s Shearwaters. Apart from bats, there were no mammals. The only land-dwelling vertebrate was a small, unassuming skink. Bermuda was a 21-square-mile speck in the Atlantic, some 600 miles from the nearest mainland, ringed with treacherous reefs that made it the region’s shipwreck capital. Early explorers were terrorized by Cahows’ nocturnal calls—guttural moans, spectral wails, and high-pitched cries—taking them for evil spirits’ voices. They called Bermuda “Isle of Devils.”
“At dusk, such a shrieking and din filled the air that fear seized us,” wrote a Spanish captain after his galleon ran aground in 1603. “These are the devils reported to be about Bermuda. The sign of the cross at them!”
The avian Eden didn’t last. In the 16th and 17th centuries, Cahows came under attack. Hungry castaways clubbed as many as 4,000 of the birds to death in a single day. To feed future shipwreck survivors, explorers stocked Bermuda with hogs, which devoured Cahows and their eggs. British ships brought colonists and other mammalian predators: rats, cats, and dogs. During a 1615 famine, the governor sent 150 settlers to survive off petrels on one of the last places they thrived. A later governor issued a decree “against the spoyle and havocke of the Cohowes”—which was, by some accounts, one of the first conservation laws in the New World. It didn’t work. For the next three centuries the birds were presumed extinct.
"By gad, a Cahow!"
Then, during the first half of the 20th century, Bermudians came upon three Cahows: one living and two newly dead. In 1951 scientists planned an expedition to find out where they nested. They brought along David Wingate, a 15-year-old schoolboy who’d found Cahow bones in a cave and grown obsessed. While searching the inhospitable islets of Castle Harbor, they spotted a bird in a cranny. One explorer used a wire noose to draw it into the sunlight. “By gad, a Cahow!” another exclaimed. Somehow 18 breeding pairs had survived in exile, hiding in rocky crevices, unable to dig their own burrows on the soilless islands. The rediscovery made international headlines. The birds were a “Lazarus species,” appearing to rise from the dead.
Wingate was determined to keep them alive. After finishing a zoology degree in 1957 at Cornell University, he returned to Bermuda, where Cahows had a shaky grip on survival. Their breeding season overlapped with that of White-tailed Tropicbirds, which nest in rocky crevices. Tropicbirds competed aggressively for nesting space, even killing Cahow chicks. So Wingate equipped the petrels’ homes with wooden doorways. Each had a Cahow-size entry hole, which tropicbirds were too large to pass through. Later Wingate designed artificial burrows for Cahows, which he nicknamed “government housing.” To construct a single burrow, 600 to 800 pounds of concrete had to be hand-mixed in buckets, then transported by boat to the rocky islets. He would go on to build dozens of them.
Wingate had another, more radical idea: a Cahow utopia. In 1963 he started reforesting Nonsuch Island, a dozen or so barren acres in Castle Harbor that once hosted a yellow fever quarantine station, a school for delinquent boys, and, before humans arrived, scores of Cahows. Wingate began transforming Nonsuch into a living museum of the petrels’ precolonial ecosystem, planting such native flora as Bermuda cedar and olivewood, culling Australian whistling pine and other invasive species. Unlike the rocky islets where Cahows had been nesting, Nonsuch was relatively high above sea level, safe from climate-charged floodwaters. He dreamed that one day the birds would recolonize it.
Wingate was named Bermuda’s first conservation officer in 1966. He went on to earn an international reputation as the Cahows’ fierce, outspoken protector. When DDT thinned their eggshells, Wingate flew to the United States to testify at one of the hearings that led to a ban on the pesticide. When a Snowy Owl killed five Cahows in 1987, he blew its head off with a shotgun. “It’s a cruel world out there,” he told reporters, “and I just had to play the role of next-level predator.”
By 2000 Wingate had grown the Cahow population from 18 breeding pairs to more than 50. Then he turned 65, the mandatory retirement age for civil servants. Stepping down was “a great, great frustration,” he recalls, adding, “I was still very fit!”
The job went to Jeremy Madeiros, a parks superintendent who’d started in conservation 16 years earlier as Wingate’s apprentice. Like his predecessor, Madeiros wanted Cahows to recolonize Nonsuch. Unlike Wingate, he wasn’t willing to wait.
Madeiros was alarmed by climate change. Hurricanes were growing stronger every year, hastening the erosion of the Cahows’ breeding grounds until the rocks were, in his words, “melting away like sugar cubes.” Meanwhile, Australian conservationists were experimenting with a technique called translocation, moving endangered Gould’s Petrel nestlings from their natal island to a second one to stabilize the population. Madeiros went to train with them for a month. Back in Bermuda, he announced a plan: move the strongest, healthiest Cahow chicks from low-lying islets to artificial burrows on Nonsuch Island. With any luck, the birds would imprint on Nonsuch and return to breed.
Wingate was skeptical. “The Cahow was so rare,” he recalls. “We didn’t dare to tamper with them too much, in case we upset their breeding.” His policy: Don’t handle the birds. But Wingate didn’t make the rules anymore. He felt sidelined. When he led tours of Nonsuch Island, he grumbled to anyone who would listen that his successor was making a mess of the place. A rift grew between the two men.
Madeiros didn’t have time to squabble. In 2003 Hurricane Fabian hit Bermuda with crushing force. Thirty-five-foot waves marched through Castle Harbor. They submerged three of the Cahows’ breeding islets, sweeping away concrete burrows and chunks of limestone. He knew he had to hurry.
The following spring Madeiros tucked 14 near-fledged Cahow chicks into tomato boxes and ferried them to Nonsuch. He was a diligent parent, handfeeding them squid, anchovies, and sardines. Then he watched them fly out to sea. During the next four breeding seasons he translocated more chicks, until he’d moved 105 in all. Finally he turned the island into what he calls “the hottest Cahow disco,” using a solar-powered sound system to broadcast the birds’ courtship cries over the water, hoping to entice them back.
Madeiros didn’t expect a new colony overnight. Young Cahows take three to six years before returning to breed. His patience was rewarded in 2009, when a pair of birds nested on Nonsuch and raised a healthy chick. In 2013 he began a second five-year project, translocating another 70 chicks. By the end of the 2020 breeding season, 30 pairs nested there.
Madeiros’s gamble is paying off for the Cahow. But success hasn’t entirely smoothed the discord with his former mentor. “It’s still there, lingering in the background,” Wingate, now 86, told me unhappily. “It got personal and nasty there for about 10 years,” Madeiros reflected. “Our relationship never recovered.”
Still, both men can agree: The Cahow’s recovery is what matters.
After our visit to Long Rock, Madeiros motored us to Nonsuch Island. At the dock, we wiped our shoes on mats doused with disinfectant—the island’s first line of defense. There are others. Rats swim over from nearby Cooper’s Island, so the forest is mined with bait boxes and pneumatic-piston traps to kill them. A plastic barrier bars invasive cane toads from colonizing the island’s freshwater pond. During a multiyear infestation, Wingate captured more than 1,000 toads and returned them to the mainland.
Strict vigilance makes Nonsuch a prelapsarian paradise. The first time Madeiros followed Wingate into the upland forest, “It was like stepping out of a time machine into a period before any human had stepped onto Bermuda,” he recalls. Two snails also once thought extinct are thriving on the island. So is the critically endangered Bermuda skink. Neither of these creatures, one might argue, is as charismatic as the Cahow. But thanks to Wingate’s holistic approach, they have a haven, too.
We hike to the south side, where Cahow burrows are strewn along the forest edge. “I’m running out of empty nests!” Madeiros exclaimed. He wants to stay ahead of the growing population but hasn’t had time to construct more housing. The Cahows aren’t helping. After almost four centuries in exile on rocky islets with no soil, they’re out of the nest-digging habit. They’re still great architects, though. Madeiros showed me a burrow where a crafty Cahow had excavated an extra room—a private nesting chamber unseeable from the observation hole.
He pointed out two other burrows, each equipped with an infrared webcam that lets fans all over the world help babysit the birds. Once Madeiros was jolted awake shortly before 3 a.m. by a call from Jean-Pierre Rouja, who launched and runs the CahowCam Project. A viewer in Japan had tweeted a tiny horror: Something that resembled a flesh-eating flatworm— or a short, sentient strand of vermicelli—had dropped onto a downy chick. Flatworms were already infamous on Nonsuch for eating another resident endangered species, the greater Bermuda land snail. Madeiros was ready to race to the island when the worm, still on camera, meandered out of the burrow.
Madeiros has another view into the birds’ lives. Two dozen raisin-size geolocators, each weighing 1.1 grams, had arrived by mail from a seabird researcher in Lisbon. He wanted to make sure they would work.
He plunged his hand into a burrow and withdrew a squirming mass of gray and white feathers. The adult sank its hooked beak into his hand, drawing blood. Cahows have bitten him many times, including on the nipple, but this one wouldn’t let go. “You sonofabitch,” Madeiros said. Disengaging the beak looked like removing a fishhook—if the fishhook could fight back.
Finally Madeiros slipped one of the geolocators on the bird’s spindly ankle. It fit.
Cahows can live longer than 40 years. Since they spend most of that time over the open ocean, geolocators and GPS tags are some of the only ways to learn where and how far they go. Since researchers first fitted Cahows with geolocators in 2009, they have seen startling results. On a single feeding trip, one bird made a 10,000-mile journey. Madeiros estimates that, in an average lifetime, a Cahow travels 2.4 million miles—the equivalent of roughly five trips to the moon and back.
The birds’ range encompasses nearly all of the north Atlantic Ocean, all the way to European borders. But the new information also opened his mind to potential challenges. Like a parent monitoring a kid on the internet, Madeiros began seeing threats everywhere. His birds might be injured by wind turbines in the Atlantic. They could become disoriented by flares on Canada’s offshore oil-drilling platforms.
Whether his concerns prove out or not, the data are already serving Cahows. Carina Gjerdrum, a Canadian Wildlife Service biologist, helped outfit the birds with GPS devices in 2019. The data showed them feeding in waters off Nova Scotia and Newfoundland, bolstering her case for classifying the Cahow as an endangered or threatened species in Canada. If the government approves the status, conservationists could push for new protections in the petrels’ habitat there.
Madeiros knows that Cahow conservation has a long way to go. Today there are 143 breeding pairs. The goal is at least 1,000, which would shift the birds’ U.S. status from endangered to threatened. As we walked back to the boat, I asked how long he planned to keep it up. Six more years, he told me. When he turns 68, the new retirement age, someone will replace him.
Miguel Mejías, 34, wants to be that someone. Growing up on Bermuda, he planned to become a marine biologist. Then he tried scuba diving. He was devastated to find that his eardrums wouldn’t equalize underwater. He felt aimless until a friend invited him on seabird surveys led by Wingate. “I absolutely fell in love,” Mejías says. “I thought it was exhilarating.” Wingate took him on as a protégé and the two became inseparable. During one early trip, he got dive-bombed by Common Terns and struck his head on a limestone pinnacle while trying to duck. He laughs about it. “David always used to say I did more damage to myself than the tern ever would,” he recalls.
Mejías is finishing a doctorate in biology. He can recite the Cahows’ history by heart, enumerating Wingate and Madeiros’s accomplishments as if retelling an Icelandic saga. He knows that, if he wants to be Bermuda’s next conservation officer, he has to wait. He thinks he’ll make “a good, strong candidate for the position,” but emphasizes that he doesn’t feel entitled to it. A lot can happen in six years, but Mejías is already dreaming, hoping to make both men proud.
“I think about it all the time,” he says. “What will my legacy be?”