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Global Warming
Seeking Higher Ground
The Bermuda petrel was presumed extinct for more than 300 years until it was rediscovered a half-century ago on a cluster of tiny, low- slung islands. Now, with seas rising, an emergency rescue operation is racing the clock to prevent the last of its kind from becoming shipwrecked.

 

Jeremy Madeiros has to watch the swells carefully to time his leap from the boat onto a light-gray limestone shelf so jagged and sharp it would shred his skin if he happened to fall. Less than half an acre and only, at its highest point, about 30 feet above the crashing waves, the islet is a godforsaken bit of rock stuck in the Atlantic Ocean off the eastern edge of Bermuda and one of four secret nesting sites for one of the rarest seabirds on earth, the Bermuda petrel—known locally as the cahow because of its eerie cry.

Madeiros, Bermuda’s terrestrial conservation officer, is a small, soft-spoken 47-year-old with a mustache, tortoiseshell glasses, and a penchant for Australian army hats. Carefully working his way across the islet’s stony surface, he makes the rounds to specially designed artificial nest burrows built to protect petrel chicks from the danger of tides and rough seas. The burrows are marked by wooden baffles that guard the entrances and have a very precisely measured oval cut into them—big enough that an adult petrel can get in to feed its chick but a hair too small for a white-tailed tropicbird to squeeze through and take over.

About a half-yard from the baffled entrance lies a concrete lid, the size of a hubcap and as heavy as a bowling ball, covering a vertical tunnel dug straight down to the nest. The dugout makes a right-angle turn to block out light, because Bermuda petrels are raised in total darkness. Lifting one of the lids, Madeiros peers into the void, where the nestling should be. “I think it’s your day, buddy,” he says, reaching in up to his armpit and pulling out a cantaloupe-sized young bird covered with fine, inch-long gray down. Soon the fuzzy layer will slough off the chick’s body, except the head, making it appear to sport a poodle haircut. Madeiros weighs the nestling and measures its wing chord (from wrist to wing tip) with a metal ruler, speaking softly in a soothing voice: “It’s okay . . . don’t worry . . . this will only take a moment.” If the wing chord is more than 190 milli-meters—about seven and a half inches—it means the bird is 18 to 20 days from fledging. This petrel measures 194 millimeters; Madeiros’s hunch is confirmed—it’s time to move.

He slips the chick and the grass from its nest into a sturdy wax-lined tomato box chosen because it might float if the box ends up in the water during the choppy, quarter-mile boat ride back to Nonsuch Island, where his precious cargo will be placed in another artificial burrow on much higher terrain. There, for the next few weeks Madeiros will be its surrogate parent, delivering hand feedings of warmed-up anchovies and squid every other day from the supply he keeps stashed in his freezer.

Pilfering a hatchling from a nest while its parents are out foraging for food hundreds of miles away might seem harsh, but Madeiros sees it as the only way to create a secure future for Bermuda’s national bird. Ornithologists were shocked by the rediscovery of the cahow in the early 1950s—three centuries after it was presumed extinct—when a handful of the birds were found holding out in the wave-sculpted substrate of several tiny atolls off Bermuda’s shores. Since then intensive management to prevent common white-tailed tropicbirds and rats from killing petrels has helped the remnant cahow population grow to somewhere between 350 and 400 birds—a level not seen since the 1600s. But now this endangered seabird is facing what appears to be the greatest challenge of all: rising seas caused by global warming. “Even a few inches of sea level rise will render the present breeding islands unusable to the cahows,” says Madeiros. “These islands are very small, and very exposed.”

Climate researchers are predicting that ocean elevation will grow much more than a few inches in the years to come. The Greenland and Antarctic ice sheets are melting faster than ever expected, according to the latest United Nations–sponsored Intergovernmental Panel on Climate Change report. Says Jonathan Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona and one of the report’s authors, “A three-foot rise in sea level is possible by 2100.”

A surge in strong storms in the Atlantic in recent years only makes matters worse. “The situation is dire,” says Steve Kress, Audubon’s director of seabird restoration, who pioneered many of the techniques used over the past 30 years to reintroduce puffins, murres, and terns to their historic nesting areas on islands off the coast of Maine. “The Bermuda petrel has suffered a lot from other problems that have brought it to the brink of extinction, particularly the introduction of predators that pushed them off most of their primary habitat. These islands provide marginal habitat, but they are crumbling. One more good wallop from a hurricane could do the species in.”

 

Although the Bermuda petrel is the national bird of Bermuda, very few people have ever seen these large nocturnal seabirds with a three-foot wingspan. For only a few months each year roughly 160 petrels pair up and raise single chicks in underground burrows on four uninhabited islands. The rest of the time the cahows are on the wing far out at sea, rocketing at speeds of up to 50 miles per hour. After their egg hatches, the parents fly off and return every couple of nights to feed the nestling with squid and small fish gathered along the nutrient-rich western edge of the Gulf Stream. When the chicks fledge at about 90 days they, too, head out to the open ocean, where they will wander for four or five years before coming home to begin prospecting for a nest site and a mate. Seventy percent of the returning cahows settle down within yards of the burrows they fledged from; the remaining 30 percent will be attracted to nearby islets by the calls of other cahows, ensuring some genetic diversity in the small but growing population of the species.

At one time there may have been as many as a million cahows scattered across Bermuda. The historical record shows the Bermuda petrel lived on these isles for millennia—their fossilized remains are found in limestone caves throughout the islands.

When Spanish conquistadores cruised along these shores in the early 1500s, they heard the cahows’ moaning and shrieking courtship calls and declared the region inhabited by evil spirits. Although they were too scared to settle on the “deviled isles,” the Spanish set loose pigs to provide food for shipwrecked sailors. The hogs proliferated, rooting up and devouring eggs, chicks, and even adult cahows. British settlers arrived in the early 1600s, and when famine struck they, too, developed a taste for the burrowing birds nesting on the forest floor “like rabbits.” The rats, cats, and dogs that came with the colonials cleaned up the leftovers. By 1621 the Bermuda petrel was considered extinct.

Then in 1935 a bird no one could identify hit a local lighthouse. The impossible had happened—it was a cahow. In 1945 another Bermuda petrel washed up on a beach. This time it was a young bird with hints of down still present, leading ornithologists to speculate there must be a nest nearby. In 1951 the American Museum of Natural History in New York launched an expedition, sending Robert Cushman Murphy to join Louis Mowbray, curator of the Bermuda Aquarium, to search for the cahow. Mowbray invited a bird-obsessed, 15-year-old local boy named David Wingate to join them. Together they explored the rocky islets within sight of the beach where the young cahow had washed ashore. At one point, the men managed to extract a seabird from a deep crevice. Holding it up, Murphy exclaimed, “By gad, the cahow!” All told, they discovered seven nests.

 

Helping to rediscover the long-lost species lit a fire under young Wingate, who went on to study zoology at Cornell University in Ithaca, New York, and came home to Bermuda in the late 1950s determined to save the cahow from extinction. As the warden of an uninhabited island nature preserve called Nonsuch, in the Castle Harbour area, and later as Bermuda’s first conservation officer, he searched every last islet for more birds, eventually uncovering a total of 18 nests. But the nesting conditions were not ideal. Traditionally the Bermuda petrel made its home in soil. The craggy crevices of the islets where it hid from predators for centuries are best suited for common white-tailed tropicbirds, which aggressively compete for the spaces. Wingate perfected the wooden baffles to shield the petrels from tropicbird raids, and hauled buckets of concrete out to the islets to construct more burrows, greatly expanding the availability of cahow breeding sites.

Meanwhile, he began the arduous task of restoring the native flora on Nonsuch and kicking out the alien predators that would be a hindrance to eventually transforming the 15-acre island into a “living museum” that re-created a semblance of Bermuda’s pre-colonial biodiversity. Rats were the biggest problem, but one of the thorniest predicaments was posed by a snowy owl—the first ever recorded in Bermuda—that took up residence on one of the cahow islands and started eating the courting subadult cahows, refusing to be chased off. “There was no doubt in my mind what I had to do,” remembers Wingate. “I felt terrible, because I’m a birdwatcher, but this owl had eaten 5 percent of the entire cahow population, and it wasn’t going to stop.” Wingate had to shoot the owl, which is now a specimen in the local natural history museum.

In 1984 Wingate took on as his assistant a young man who grew up on Bermuda and studied field biology in England, Jeremy Madeiros. “Everything about the cahow project drew me in,” says Madeiros. “I saw that this species had a chance of coming back, and I wanted to be one of the people who made that happen. It really takes a long-term commitment to help a species recover, and I knew I was in this for the long haul.”

When Madeiros succeeded Wingate as Bermuda’s terrestrial conservation officer in 2000—Wingate now works with Bermuda Audubon—he faced a grim reality: Although the number of cahow breeding pairs had almost doubled, the birds were running out of what little dry land they had left. “Hurricanes are the ultimate shapers of islands in Bermuda,” Madeiros says. “I was becoming very alarmed by the storm damage to the nesting islands—we were at the whim of every single weather system. I fixed in my mind that getting the birds to nest on Nonsuch was the key to the species’ survival and that we had to do this. I didn’t want to be sitting around 15 to 20 years from now regretting not doing this program.”

Moving cahows to higher terrain wouldn’t be easy, but other researchers had already developed successful techniques to help lure seabirds back to islands where they once nested. Madeiros was closely following one particular relocation project with the Gould’s petrel, a relative of the cahow. Gould’s petrels had been in serious trouble a decade before because introduced rabbits had destroyed most of their breeding habitat on islands off the east coast of Australia. After removing all the rabbits from one island, Nicholas Carlile, a scientist with the Department of Environment and Conservation of New South Wales, had managed to quadruple the endangered Gould’s petrel population, from 250 to 1,000 breeding pairs. Carlile relocated some of the offspring to a second island, eventually creating a new breeding colony, with more than 50 birds.

The same techniques could work for the Bermuda petrel, Madeiros reasoned, and he would add some insurance: solar-powered stereo speakers broadcasting the cahows’ prerecorded mating calls from sunrise to sunset throughout November, when mature adults are searching for mates and nest sites. This “playback” technique had proved extremely helpful in Steve Kress’s work luring puffins back to breeding isles in Maine, and it would advertise to the cahows that Nonsuch had become a hot spot for meeting singles.

 

If Madeiros had any lingering doubts about the need for relocating cahows, they were blown away in late September 2003, when Hurricane Fabian smashed into Bermuda, washing 35- to 40-foot waves over three of the cahow islets. It wasn’t breeding season at the time, so no birds were killed, but the storm destroyed 40 percent of the burrows, which he and his crew had to work frantically to rebuild before the cahows returned to nest a month later. “Hurricane Fabian was a huge wakeup call,” says Madeiros. “If Fabian had been a category four hurricane instead of a three, we could have lost two of those islands then and there, and they did partially collapse.”

The following spring Madeiros began moving about 20 nestlings each year to artificial burrows on Nonsuch, leaving some chicks behind on the islets to allow the existing populations to continue their climb. “All we need is a nucleus of two or three pairs of breeding birds on Nonsuch,” he says, “and that will be enough to begin to build a new colony.”

Right now his most pressing objective is to remove the chicks from the island where Wingate first helped rediscover the cahow a half-century ago. The limestone here is more crumbly than on any of the other cahow islets, and giant slabs of rock are collapsing into the sea—a clear manifestation of a region undergoing rapid, irreversible change. “This is a very dangerous place to be breeding,” says Madeiros. “On Nonsuch they will be safe from hurricane flooding and erosion, and have enough soil that they may eventually dig their own burrows—we won’t have to do it for them.”

The most recent evacuee is settled into artificial burrow No. 831, 37 feet above sea level and just steps below the 19th-century house where Madeiros stays with his wife and two children during summers. In a few weeks the young petrel will emerge to explore the area on foot and to exercise its wings, flapping them back and forth for as many as eight nights. By using its hooked beak and the little claws on the end of its webbed feet, a cahow can climb a tree trunk in search of the perfect place to launch toward the ocean. When the time comes, the petrel peers intently at the horizon, as if to memorize the landmarks, sea stacks, and islets, then preens every single feather. Finally, it hitches itself up to a chosen launching spot, bobs its head a few times, spreads its wings, and pushes off.

Although Madeiros has watched the departure over and over, he’s nervous every single time they make that leap toward the sea. So far, 79 relocated Bermuda petrels have fledged from Nonsuch and only one died—it had a congenital wing deformity that wasn’t noticeable until it tried to fly and plummeted into the ocean. Carlile told Madeiros to expect 15 percent mortality, so the cahows are way ahead of the curve.

As each petrel leaves, Madeiros says, he feels the anxiety of a parent sending his kid off to college—he’s done everything he can to prepare the young bird for life on the wing, and he hopes it will return in four years to get ready for a chick of its own. Experience tells him that only about one-third of the fledglings will make their way back. Half of them won’t last even two weeks in the wild, primarily because they will fail to figure out how to find food without help.

Still, he has faith that some of his brood will come home to Nonsuch. “These birds have proven that they are tough survivors,” he says. “And I’m pretty confident that ability is going to ultimately bring them through.” Next November will be the initial test—the fourth year of the project, when the first of the relocated cahows might swoop in low over the island to check out the mating scene. Anxiously anticipating their arrival, Madeiros will bundle up and go outside into the cool ocean air and strain into the darkness of the fading twilight to see the first shadowy figures streaking toward land and to hear their haunting calls.

WHAT YOU CAN DO
You can help protect Bermuda petrels and other seabirds from rising seas by taking important steps to halt global warming (to find out how, click here. Additionally, join beach cleanups to help prevent seabirds from eating harmful bits of plastic; keep a firm hold on balloons and cut up your old fishing lines so seabirds won't become entangled; properly dispose of used oil to prevent it from running off into water sources and eventually the ocean, where it could ruin the waterproofing on birds' feathers; keep pets away from seabird nesting sites; and join Bermuda Audubon.

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Crash Course

Rising seas are not the only problem facing birds that nest along coastlines. Scientists are beginning to see worrisome signs that global warming might be creating food shortages for some seabirds. Take, for instance, the Cassin’s auklet on the Farallon Islands, off the California coast, whose population has plunged from 105,000 birds in 1972 to about 15,000 today. The auklets suffered near total reproductive failure in the past two mating seasons—an event unprecedented in 35 years of continuous research. “It appears to be linked to the timing of changes in ocean currents leading to little productive upwelling at the right time in the area where the auklets feed, and very strange ocean conditions like anomalous winds leading to little available krill,” says Russell Bradley, the Farallon program manager for Point Reyes Bird Observatory Conservation Science. “We never saw complete breeding failure before, even during major El Niños.”

In Scotland many seabirds rely on sandlances (known locally as sand eels) for food in the North Sea, where sandlances are becoming smaller than normal as well as harder for the birds to find. Scientists suspect that the rapid warming of the shallow North Sea—3.6 degrees Fahrenheit in the past 20 years—might have ultimately caused the sandlance population to crash. Morten Frederiksen, a biologist with the Centre for Ecology and Hydrology in Scotland, says the three last seabird breeding seasons have been among the worst recorded in the country. The population of one species, the black-legged kittiwake, has dropped in half since 1990 along the country’s east coast, and from about 54,000 in 1988 to 16,732 in 2002. Recent estimates suggest that there are only about 1,000 pairs left on the islands. “There’s little evidence to suggest that seabirds in the North Sea can adapt to eating other food,” says Frederiksen. “In the long term, reducing the rate and extent of global warming is likely to be beneficial for marine ecosystems and for the seabirds that depend on them.”—R.D.

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On the Case
Animal population ecologist Morten Frederiksen talks about the precarious future of seabirds in northern Scotland.

A Living Legend
A recent documentary recounts a decades-long quest to find—and save—the Bermuda petrel.

















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