Bermuda Petrel or Cahow

(Pterodroma cahow)

I have been fascinated by petrels ever since I read Tom the Water Baby as a child. In that old classic, it was the Stormy Petrel, called “Mother Carey’s Chicken,” who came into the story. Mother Carey is the name petrels have long been called by sailors, who meet them far from shore, at home in the wilderness of the oceans. The name is thought to be derived from Mater Cara, which is how the early Spanish and Portuguese sailors, the first Westerners to sail the southern seas, referred to the Virgin Mary. And petrel is thought to refer to Saint Peter, because when they feed, the birds seem to be walking on water.

The subtropical petrel whose story I share here, the Bermuda petrel, is one of the so-called gadfly petrels belonging to the genus Pterodroma—from the Greek pteron, meaning “wing,” and dromos, meaning “running”: hence “the winged runner.” This recognizes the fast, acrobatic, and gliding flight. Indeed, all petrels are masters of the air, able to survive fierce storms and fly through howling winds with the wild spray of giant waves crashing below them. It is when they come on land to breed that they suffer so terribly from the damage that we have inflicted on their island environments.

The local name for the Bermuda petrel is the cahow, a word said to derive from the species’ eerie nocturnal cries. These initially protected Bermuda and its isles from settlement, because the Spanish sailors believed they were inhabited by evil spirits. Indeed, Bermuda was once referred to as the “Isle of Devils.” In those days, in the early 1500s, when Bermuda was discovered by the Spanish, it is estimated that at least half a million cahow returned each breeding season to the coastal forests of Bermuda and the surrounding islands, nesting in burrows in the sandy soils.

Unfortunately the “evil spirits” did not prevent the sailors from landing in search of fresh food and water. And they put pigs ashore to breed to provide a future supply of fresh meat. Thus began the destruction of the cahow’s nesting grounds. And then things got worse. The British, quickly realizing that birds rather than spirits produced the strange sounds, began to colonize the beautiful tropical island, and the early settlers brought with them the usual invasive species. Also, year after year, while the petrels were away at sea, the British took over the cahow’s nesting grounds for farming. And when the petrels returned for the breeding season, they were killed for food in great numbers—despite the birds being given official protection when the governor made a proclamation “against the spoyle and havocke of the Cohowes.” Surely one of the earliest conservation efforts ever!

By 1620, it was believed that the cahow was extinct. Except that, just occasionally, someone reported otherwise: In 1906, for example, a cahow was actually collected, although it was not identified as such at the time. And then in 1935, a fledgling cahow hit a lighthouse—and its dead body proved conclusively that, somewhere, a population still survived. World War II temporarily put an end to speculations about their existence. But the death of that fledgling caught the imagination of a local schoolboy, David Wingate.

The Cahow Lives

“The year that fledgling collided with the lighthouse,” David would remember, “was the year that I was born.” He told me this during a telephone conversation in 2008. He vividly recalled sitting in his kayak one day, looking toward the islets beyond the lighthouse, and thinking: “It was only fifteen years ago when that young cahow died. Perhaps, just perhaps, they are still out there. Somewhere.” He told me that the hairs on his neck stood on end at the thought.

Nor was he alone. Dr. Robert Cushman Murphy, of the American Museum of Natural History, managed to get funds for a thorough survey to find out, once and for all, the truth about the cahow. And when, in 1951, he set out along with the director of the Bermuda Aquarium, David was invited to join them. What a thrilling day for a sixteen-year-old schoolboy to be present when they came upon seven nesting pairs of Bermuda petrels on a tiny islet off the Bermuda coast. (Subsequently they found eleven more pairs on another three islets.) “I could hardly believe in my good luck,” David said. “It was a dream come true. And from that moment I knew my life’s path.”

Somehow the cahow had survived against seemingly impossible odds—but there were so few of them. Could the newly rediscovered colony possibly survive much longer? Without the determination and energy of David Wingate, who devoted much of the rest of his life to their cause, they probably would not have, for their situation back then was desperate.

The four tiny rocky islets (off Castle Harbor, east of Bermuda) where the tiny remnant of the once huge cahow population had been forced to nest shared a total area of only just over two acres. Moreover, these islets were, to all intents and purposes, devoid of vegetation, and the small, shallow pockets of soil were quite unsuitable for nesting burrows. The cahows were laying their single eggs and raising their single chicks in rock cavities almost at sea level. And the islets, situated at the edge of the protective reef, were subject to severe battering by stormy seas. On top of all this, during the 1960s high levels of DDT were measured in both chicks and eggs, and this almost certainly had an adverse effect on their reproductive success. Indeed, according to David it reduced breeding success by about half. (David had become involved in the fight to ban DDT described in part 2 in the chapter on the peregrine falcon.)

And finally, as if all this were not enough, the petrels suffered in competition with the larger, more aggressive, and still common white-tailed tropicbirds. The cahow lays in January; chicks hatch in March. The competing tropicbird nests later, and on finding a nest site occupied will force a cahow chick out and take over. In some years, petrel chick mortality has been as high as 60 percent as a direct result of this competition for nest sites on the inhospitable islets.

A Nesting Real Estate Business

One of the first steps taken to assist the few remaining cahow was to fit each existing nest site with a wooden baffle that prevented the entry of the larger tropicbirds. Next, a number of artificial nest sites were constructed, each consisting of a long tunnel ending in a concrete chamber. Both these measures led to increased breeding success. And from that time on, the biologists working to save the cahow have ensured that there are at least ten extra nests ready for each breeding season. It has been necessary also to repair those damaged by the storms that have become worse due to rising sea levels. “Before 1989,” David told me, “we never had real problems with flooding.” But in 1995, some 40 percent of nests were damaged by a hurricane; in 2003, when the area was devastated by Hurricane Fabian, 60 percent of nest sites were destroyed and massive chunks of the islands were lost. It was fortunate that the hurricanes occurred when the cahow were at sea.

Because of the worsening situation, a new set of nest burrows was constructed on the most elevated part of the largest nesting islet—eight feet higher than the nests destroyed by Hurricane Fabian. Breeding pairs found scratching in the debris of their old nest sites were attracted to the new site when they heard recorded playback of cahow courtship calls, and one couple was captured and physically moved there! Three pairs nested in the new burrows.

In the early spring of 2008, I was able to speak to another dedicated advocate for the cahow, Jeremy Madeiros. Jeremy first became involved in 1984 in his late twenties when he was accepted as a training apprentice under David Wingate in what was then the Department of Agriculture and Fisheries. As a boy, Jeremy had preferred poking about for insects and plants over kicking balls around with his friends. The experience he gained working with David—not only on the recovery of the cahow, but also in the efforts to restore Nonsuch Island as a new nesting ground for the species—was just what he needed. He went to college and got the qualification that eventually landed him a job as a parks superintendent. He was able to maintain his connection with David as he followed in his footsteps.

Learning to Live with Danger

Above all, Jeremy needed to learn to cope in often dangerous conditions—“to work without killing or injuring myself,” is how he put it during a long telephone conversation we had. Knowing that David took huge risks, I asked Jeremy what it had been like to work with him. He laughed and told me about something that happened in the early 1990s when the two of them were monitoring the progress of the cahow chicks. This is done at night, when the chicks come out of their nest burrows to explore and stretch their wings. David decided to start the monitoring on an islet where they knew there were two nests. With only the light from their flashlight (the chicks do not come out in moonlight, which would make things so much more convenient for humans), they had to maneuver the little boat close to the rocky shore in a high swell.

“We had to jump onto a rock and quickly scramble up before the next wave covered it,” said Jeremy. Then they had to get to the far side of the islet, which meant climbing a steep cliff as there was no access by boat. They got there safely and, as always, had a wonderful time watching the chicks. It was on the way back that disaster so nearly struck.

“David was having trouble with his back,” Jeremy told me, and had taken a foam rubber cushion to sit on the sharp rocks. At one place they had to jump down ten feet onto a rock below—a rock that was flanked, on either side, by a twenty- to thirty-foot drop onto jagged rocks and crashing waves.

“He asked me to go first,” said Jeremy, “and then he threw down the cushion and asked me to put it on the rock. He thought it would lessen the jarring to his spine.” Imagine Jeremy’s utter horror when David landed safely—only to bounce right over the edge and vanish from sight. “I hardly dared shine my torch down,” Jeremy said, “I was so sure I would see a mangled body way down below.” How could anyone survive such a fall? And if he had survived, how could he, Jeremy, possibly get there with the boat to rescue him?

“I nervously shone the torch down,” Jeremy said, “and there were two eyes looking up at me.” Somehow David had managed to grab onto a jagged rocky outcrop. He was battered and bloody but very much alive, and with Jeremy’s help he managed to scramble back up. And insisted they visit the other chicks on their list!

A New Home for the Cahow

After Hurricane Fabian destroyed so many cahow nesting sites, it became clear that the birds’ long-term survival would depend on the restoration of some of their original nesting habitats. And this is where the future of the cahow becomes linked with David’s extraordinary restoration work on Nonsuch Island (described in the sidebar). When the time came to start a new colony of cahow on the restored island, a blueprint for the translocation of petrel chicks already existed: Nicholas Carlile and David Priddel had successfully established a colony of endangered Gould’s petrels on a new island—the whole fascinating story is told on our Web site.

“We could not have risked trying relocation with the cahow if we had not known of the success of Nicholas’s work with the Gould’s petrel,” David told me. “The cahow were still in such a precarious state.”

In 2003, Nicholas joined the cahow restoration project. He assisted in designing a recovery plan that had the ambitious goal of moving a hundred young birds to Nonsuch Island over a five-year period. The first of these translocations was made that year—ten chicks, three weeks before fledging, were taken from their nests on the islets to artificial burrows constructed for them on a by-then rat-free Nonsuch. They were fed each night, and their growth and behavior recorded.

Nicholas had found that it is very important not to move chicks too late. It is when they first leave their nests to look around (about eleven days prior to fledging) that the location of the nest is imprinted in the brain, so that it will be that place—rather than the spot where they hatched—to which they will subsequently return, three to five years later, to nest themselves.

When those first chicks were moved, Jeremy worried a bit. They were going from bare rocks to wooded slopes—would they be able to cope?

“Nicholas was there when we moved the first youngsters,” Jeremy told me. “We were amazed as we watched a chick emerge from its nest burrow, stretch its wings, and move around exploring. Suddenly it came to a tree. It stopped, looked up—and immediately scurried right up the trunk like a squirrel, using its sharp little beak and claws, and sort of hugging the trunk with its wings. Right on up to the top!” Of course, when they thought about it, this made sense. Tree climbing is probably deeply encoded in the birds’ ancestral memory, for in the old days, emerging from their burrows in the forests, they would have climbed in order to take off to sea from the treetops. Since then the poor things have been reduced to climbing up bare rocks.

“After that,” said Jeremy, “I realized why the chicks on the islets so often climbed up David and me and fledged from the tops of our heads. We were the closest thing to a tree in their abnormal world of rock!” Jeremy paused and laughed. “They often left their mark on our heads before they left,” he said. “But that was okay—it’s supposed to be lucky!”

All of the first ten translocated chicks fledged successfully and flew off to spend the next few years at sea. The following year, twenty-one were moved, and again they all fledged successfully. Just before the 2008 breeding season, eighty-one out of the planned hundred have been successfully moved, and seventy-nine of them have fledged and departed safely.

Stop-Press News

Recently I received news from Jeremy. “I said I would let you know if anything exciting happened,” he wrote. “I am happy to report (with a big smile on my face!) that just such a thing has now happened!”

But first he reported on the situation of the original four tiny breeding islets where the population is continuing to grow. Originally there were just eighteen breeding pairs—but the number has now risen to eighty-six. “It seems that, perhaps because the colony is getting bigger—which they love—there is more pair formation going on,” said Jeremy. “It is as though they have changed to a higher gear. And once the critical mass has been reached, there will be more and more pairs each year. Then they will be on their own.”

When he wrote, Jeremy was busy checking the weight, wing growth, and plumage development of the forty chicks hatched on the islets in 2008, twenty-one of which will be moved to Nonsuch. And if all twenty-one fledge successfully, this will mean that their goal will have been reached: One hundred cahow chicks will have been moved to and fledged from Nonsuch during the first five years of the project.

Next, Jeremy shared his really exciting news. In mid-February 2008, he was on Nonsuch carrying out some repairs to the solar-powered sound system that has been installed at the new nest site. It plays back courtship calls to encourage any cahow within hearing distance to investigate. Jeremy decided to stay overnight on the island to see how it was working.

“About forty-five minutes after nightfall,” Jeremy told me, “the first cahow swept in from the open ocean and started circling above the translocation site; more came in and began to carry out acrobatic high-speed courtship flights until within another hour I could see a maximum of six to eight birds at once. Sometimes they circled high above; sometimes [they] made low, acrobatic high-speed courtship flights just above the artificial nest burrows, often making their eerie moaning calls.”

Eventually, some of the birds began to land among the burrows, “culminating with one bird landing right beside me! I was able to just reach right over and gently pick it up without any fuss.” Jeremy confirmed from its band number that it was indeed a bird that had been moved to Nonsuch as a chick in 2005. “My heart just leaped when I realized that this bird had not just survived the last three years at sea after being partly raised by us, but had in fact returned to its point of departure as hoped!”

More cahows were recaptured at the site over the next month or so, and all were the birds that had been translocated. In mid-March, one of them was found for the first time staying for a whole day in one of the Nonsuch burrows, excavating a large pile of soil outside the nest entrance, digging a nest scrape in the nest chamber, and pulling in nest material. “A sure sign that this bird has now ‘claimed’ this burrow,” said Jeremy. I could hear his excitement as he told me that he had checked its band and found that this was the exact same burrow to which it had been moved in 2005! “And,” he said, “I had watched it fledge to sea during a night watch in June 2005. How amazing to think it has carried out a perfect ‘return to the point of departure’ after living God knows where out on the ocean!”

In all, four cahows translocated to Nonsuch in 2005 were captured near the nest burrows. Between six and eight were observed some nights flying over the site; at least six nest burrows received prospecting visits, some more than half a dozen times. And cahows have stayed over for the day in three of these burrows on several occasions. Jeremy thinks those birds were probably males, which seem to return a year or two earlier than the females, and he hopes that next season they will return and start attracting females to their burrows. “And by then, the first of the 2006 translocated cohort should also be joining them. I can hardly wait!”

When the cahow that fledged on Nonsuch return to breed there themselves, it will be a major milestone in the restoration of this resilient seafaring bird and a tribute to the determination of Jeremy Madeiros, Nicholas Carlile, and, above all, David Wingate, who fell in love with the cahow as a schoolboy fifty-nine years ago.

The name of Carl Jones is synonymous with restoration of endangered species on Mauritius. Shown here with the dazzling, emerald-green echo parakeet, the last of perhaps as many as seven parakeet species once found on the islands of the western Indian Ocean. (Gregory Guida)