Off the eastern coast of Bermuda in Castle Harbour sits a jagged, lush island by the name of Nonsuch. Spanning just over 16 acres, Nonsuch is one of Bermuda’s most isolated islands, and it houses several endangered and Lazarus species (those that were once thought to be extinct). Among the dense forests filled with lizards, insects, and birds, ornithologist Jeremy Madeiros spends most of his days living in a repurposed quarantine hospital, making him the island’s sole human inhabitant.
On Nonsuch, you can find “almost all of the native endangered species in Bermuda,” said Madeiros, who is the senior terrestrial conservation officer for Bermuda’s Department of Environment and Natural Resources. “For some species, this is the last place on Earth where they survive.” Over the past two decades, Madeiros has dedicated his career to conserving the Bermuda cahow—the archipelago’s national bird, which doesn’t exist anywhere else on the planet.
When Spanish seafarers first arrived on Bermuda’s shores in the early 1500s, Madeiros’ research suggests, cahows numbered at about 500,000 breeding pairs. Historical records show that the Spanish mistook the harsh cries of the cahow for demons and the souls of shipwrecked sailors, and this kept them from settling the island. However, they brought with them hogs that preyed on the cahow. Things only compounded when the English arrived about a century later and introduced rats, cats, and dogs. They also ate hundreds of the cahows each day to avoid famine. So successful was this slaughter that Bermuda’s English governor issued a decree in 1616 against “the spoyle and Havock of the cahowes … which already wer almost all of them killed and scared awaye very improvidently by fire, diggeinge, stoneinge, and all kinds of murtheringes.”
Unfortunately, the proclamation came too late, and by 1625, the cahow was considered to be extinct. It wasn’t until 1951 that 18 breeding pairs were miraculously found on several islets near Nonsuch. Now, 70 years later, Madeiros is leading the effort to keep this fragile species alive. The work has been so successful that conservationists across the globe are using the same methods to protect other endangered seabirds that are suffering from the perils of climate change.
The cahows’ plumage is a pattern of dark gray and white, and their long wings span 36 inches. They wander the open ocean for up to six years in search of food like squid and small fish, landing only on the water to rest. They then return to Bermuda twice, once in October to early November to mate, and again in January to lay a single egg in underground burrows or deep rock crevices. But these eggs are fragile, and about half fail to hatch. The chicks that do hatch take a few months to mature before flying out to sea to try to survive on their own. Unfortunately, only 28 to 38 percent of the fledged chicks make it through their first year and return to breed, resulting in slow-growing populations.
After the rediscovery of the cahow, Bermuda local and ornithologist David Wingate dedicated his career to their conservation. In 1960, Wingate started the Cahow Recovery Program, which aimed to control threats to the birds, better understand their breeding biology, and grow their population in the Castle Harbour Islands Nature Reserve, which includes Nonsuch, three surrounding islands, and a handful of rocky islets. In 2001, Madeiros took over the program. At this point, there were 55 breeding pairs—a significant increase from 1951, but not nearly enough to move the bird from the critically endangered category. Madeiros’ first objective was to relocate the birds from the low-lying, rocky islets—which are being destroyed by sea level rise, hurricanes, and erosion—to the larger and more elevated Nonsuch Island.
He traveled to Australia to observe how they moved the endangered Gould’s petrel from one area to another to establish new colonies—a technique known as translocation. In the case of the cahows, this involves closely monitoring the growth of a group of chicks and moving them to Nonsuch right before they are old enough to fly. If they are moved too soon, Madeiros must spend significantly more time feeding the chicks and risk losing some. Too late, and the birds will have already imprinted on their surroundings, causing them to return to the islet they were born on after their years of maturing out at sea. This is concerning, as two of the rocky refuges are at risk of disappearing overnight if another big hurricane hits, said Madeiros.
Once translocated to Nonsuch, the chicks are placed in snug artificial burrows that are concrete holes in the ground, which offer them a safe area to nest. The hope is that they will imprint on Nonsuch and come back to these burrows to breed, thus establishing a more secure colony for future generations. Thanks to two successful translocations, more cahows returned to Nonsuch this year than ever before to lay eggs, 13 of which hatched in March. Throughout the reserve, there are a total of 71 chicks and 142 breeding pairs. “It’s really improved beyond my wildest, most optimistic dreams,” Madeiros said.
Madeiros also installed tiny infrared cameras in the artificial burrows, allowing ornithologists and bird lovers worldwide to watch the birds in real time and learn more about their nesting and breeding process. “The details behind everything that happens in those burrows was basically unknown before,” said Charles Eldermire, leader for the Cornell Lab of Ornithology Bird Cams project. Eldermire is collaborating with Madeiros to get the word out about the cahow. Now, they have more information on how adults copulate, when they come back to feed their young, and how often they incubate the chicks.
The cameras have also offered a window into nest invasions by other birds, mammals, crabs, and lizards that are hard to study. Thanks to people keeping an eye on the live feed, researchers learned about a flatworm that invaded a cahow nest one year. “Viewers are also great at noticing when something different appears to be happening,” said Eldermire, “like detecting slight variations in behavior or the physical aspects of the adults.”
Yet the cahow is still considered one of the rarest seabirds in the world. The long-term goal is to restore the species to 1,000 breeding pairs, which will move them from endangered to threatened. To do this, Madeiros must relocate the birds that are still on the islets to Nonsuch before their homes are destroyed. “There are now yearly hurricanes with 30-foot waves coming over the reef and hitting the islands,” said Madeiros, who is currently traveling out to Nonsuch regularly to monitor the new chicks.
There is also concern about rats, which can swim from the mainland to the cahows’ nesting grounds and devour the eggs and chicks. “It’s a constant battle every year to intercept the rats,” said Madeiros. However, through rigorous eradication efforts, they’ve been able to keep most of the cahows safe. “This is the last area in Bermuda where we can manage to exclude mammal predators and control humans,” he said.
Because the Cahow Recovery Program has been such a success, conservationists around the world are implementing similar programs to save a variety of birds. In Hawaii, for example, the endangered Hawaiian petrel is being moved to a protected haven in the Kīlauea Point National Wildlife Refuge. Just last year, the first of the 87 birds translocated as chicks returned after several years out at sea—a good sign for the species. And with seabirds being among the most imperiled family of birds in the world, this technique will likely become more popular in the years to come.
But translocations are extremely labor-intensive, and there are other steps that should be taken before moving bird colonies, said Stephanie Borrelle, the marine and Pacific regional coordinator for BirdLife International. “It’s easier when you can find remnant populations or colonies and do restoration actions on the island.” This includes removing invasive species and predators, building artificial burrows, and controlling soil erosion.
Regardless of the methods used, protecting seabirds is crucial for marine ecosystems. Many of these birds are top predators and they bring key nutrients back to their breeding grounds, affecting plant growth. They also allow scientists to better understand the ocean’s health. “Seabirds are indicators of the ocean—the canary in the coalmine,” said Borrelle. “They tell us where there is plastic, what the status of the fisheries are, how birds are breeding.”
By protecting the cahow, Madeiros also hopes to educate locals about their exceptional national bird. “Most Bermudians didn’t know a lot about the bird 20 years ago,” said Madeiros. “Now, we hope the birds will be safe for centuries.”