Discovering Bermuda’s cahow country

On Bermuda’s Nonsuch Island, a protected nature reserve, a rare species of seabird is making a comeback 

  • Aug 29, 2019
  • 1,255 words
  • 6 minutes
A view of Nonsuch Island in Castle Habour, Bermuda. (Photo: Michela Rosano/Canadian Geographic Travel)
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Castle Harbour is choppy when our pontoon boat docks at Nonsuch Island, a jagged chunk of volcanic sediment off the coast of St. George’s Parish in Bermuda. Jeremy Madeiros, senior terrestrial conservation officer for Bermuda’s Department of Environment and Natural Resources, greets our group of journalists on a shoddy limestone pad serving as a dock.

Only a handful of non-scientists have set foot on this protected island since it became part of the Castle Harbour Islands Nature Preserve in 1960. Madeiros is the island’s lone human inhabitant. Since 2000, he has lived here part-time in a modest house originally built as a quarantine hospital ward with million-dollar views of the Atlantic. While here, he works day and night to recover endemic Bermudan wildlife species, including one of the rarest seabirds on the planet: the Bermuda petrel, or cahow, as it’s known locally.

As soon as we step onto the island, Madeiros, clad in a denim shirt and khaki pants, directs us to dip the soles of our shoes in a bleach bath to remove any pathogens from the mainland that could harm the fragile native species on Nonsuch. As he leads us up a staircase carved into the limestone cliff to the cahow nesting sites on the island, I feel like I’m entering Jurassic Park.

On the way up, Madeiros points out man-made nesting boxes built for the white-tailed tropicbird. “Longtails have a rough and tumble existence,” he says of the ivory birds that share the island with the cahows. “They look like angels and fight like devils. With the cahows, it’s the opposite.”

The entrance to Nonsuch Island Nature Reserve.
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Jeremy Madeiros shows a group of journalists a manmade cahow burrow on Nonsuch Island.
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A white-tailed tropicbird, or longtail, another native Bermudan seabird, using an artifical nesting box on Nonsuch Island.
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Outside of Bermuda, most people have probably never heard of the little seabird that Madeiros has dedicated much of his career to managing, but the cahow is part of Bermudan history (it also happens to be the country’s national bird). When Spanish sailors stumbled upon the North Atlantic island surrounded by ship-wrecking reefs in the 16th century, they were spooked by strange sounds coming from shore. It was the cahows, which were numerous throughout the Bermuda mainland at the time. The birds’ vocalizations were so eerie, the sailors decided the island must be inhabited by demons and nicknamed Bermuda the ‘Isle of Devils.’

While the Spanish didn’t stay long, they did leave a few hogs on the mainland. By the time the British arrived and colonized Bermuda in the 1600s, those hogs had wiped out as much as 90 per cent of the cahow population, and all of their breeding grounds on the mainland (cahows nest in burrows on the ground). The rest of the cahow population was wiped out by the British (cahows were an easy meal), along with the rats, cats and dogs they brought with them. By 1620, the cahow was thought to have gone extinct — and it stayed that way for more than 300 years.

The cahow is one of just 11 “Lazarus species” in the world, so-called because they “came back to life” from extinction. In 1951, David Wingate, Bermuda’s first conservation officer and Jeremy Madeiros’ predecessor, along with Robert Cushman-Murphy of the American Museum of Natural History, and Louis B. Mowbray, curator of the Bermuda Aquarium, found a tiny cahow population of just 18 breeding pairs on a smattering of tiny, razor blade-sharp islets in Castle Harbour. That prompted Wingate to start the Cahow Recovery Project, one of the world’s first long-term species management, research and recovery programs, in 1962 on three islets. Madeiros took the reins in 2000, and in 2004, after hurricane surges threatened the birds once again, he decided to establish a new colony on nearby Nonsuch Island, which offers much larger and more sheltered breeding grounds. 

“The first pair nested on Nonsuch in 2009, and now we’re up to 22 pairs, so Nonsuch is rapidly become the second largest nesting colony,” says Madeiros, adding with a smile, “It’s one of the most successful examples of low-cost government housing.”

In the past 19 years, the entire cahow population on Nonsuch and the other Castle Harbour islands has swelled to 131 pairs — no small feat for birds that lay just one egg per year.

Jeremy Madeiros holds up a cahow chick.
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Jeremy Madeiros records a chick’s weight and wingspan by an artificial burrow.
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As we walk further onto the island, I realize that Madeiros hasn’t stopped talking about the cahows since we stepped off the boat. He’s a never-ending fountain of knowledge and enthusiasm for these birds, and it’s most apparent when he demonstrates his daily routine during the winter and spring breeding season: monitoring and caring for cahow chicks.

“The birds I’m working with now, it’s likely that they’re going to outlive me,” he says, referring to the cahow’s incredible 50-year lifespan. Madeiros stops by burrow 821, one of 45 artificial nests about the size of a large flowerpot spread across two colonies on the island. Some burrows are now fitted with infrared cameras, allowing researchers 24/7 access to study the chicks and their behaviours (the public can watch too on the Nonsuch Expeditions CahowCam). Crouching down, Madeiros removes the lid from the burrow, reaches in and pulls out a handful of grey fluff with a beak. Just three weeks old, the cahow chick — named Spirit — is carefully weighed and measured, before Madeiros pops it back into the burrow. In total, he now oversees cahow chicks at more than 300 nest sites at 10 locations around Bermuda.

About 80 per cent of the cahow population on Nonsuch now uses these burrows, Madeiros tells us, and nesting sites like this are the species’ only chance at rebuilding a healthy population. Though there’s little information on the cahow’s seafaring life, they leave the Castle Harbour islands in the summer and are thought to fly 2,000 kilometres to the northeastern coast of the United States and Maritime Canada to feed on small shrimp and squid. They stay until October, then return to Bermuda.

Madeiros leads us along a trail through a dense forest of Bermuda cedar, bay-grape trees, olivewood and 10,000 other native and endemic plant species that he and Wingate helped reintroduce as part of the ecological restoration program on Nonsuch. At the end of the trail, we emerge onto one of the most picturesque beaches I’ve ever seen. Thick clumps of golden seaweed dot the quintessential pink sand that attracts scores of tourists to Bermuda each year, as cerulean waves lap the shore. Beside us at the trailhead is a 14-metre-long and two-metre-high wall of plastic debris that Madeiros and his colleagues pulled from the beach in just 18 months. It’s a sobering reminder of  the new threats that await the cahows beyond their sanctuary.

Sargasso seaweed lines the beach on Nonsuch Island.
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Getting to Nonsuch Island

Public access to Nonsuch Island is generally restricted due to the sensitivity of the cahows and other native species. However, the Bermuda Zoological Society does offer guided tours of the island for a limited number of lucky visitors each year from March to June and September to November. Guests board the RV Endurance from the dock at the Bermuda Aquarium to Nonsuch Island, where they learn about its history and the ecological restoration work happening there. 

Visitors looking to do some cahow watching without visiting Nonsuch can charter a boat from the aquarium and ply the waters around Nonsuch for an afternoon of snorkelling shipwrecks (Bermuda has many) and cahow spotting (in the fall) from the boat.

For more information on the cahows, including the CahowCam, and Nonsuch Island, visit Nonsuch Expeditions.


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