Future Is Bright For ‘Extinct’ Cahow

Bermuda’s Nonsuch Island is now the chief battleground in the Cahow’s war against extinction — and for the first time in centuries, the critically endangered national bird appears to have gained the upper hand.

The re-discovery of Bermuda’s Cahow – a species thought to have been extinct for more than 300 years — is one of the great stories of survival in the annals of natural history.

Believed to have been wiped out within decades of Bermuda’s settlement, over the centuries there had been tantalising hints a small population of Cahows may have defied the odds and survived on the remote Castle Harbour islands.

In 1935 an unknown bird which crashed into St. David’s Lighthouse was tentatively identified as a Cahow by no less an authority than American naturalist and explorer William Beebe, then conducting his bathysphere dives from Nonsuch Island.

Led by Robert Cushman Murphy of the American Museum of Natural History and the Bermuda Aquarium & Zoo’s Louis Mowbray, a major expedition was finally launched in 1951 to try and locate a surviving Cahow colony. A Bermudian schoolboy with a flair for ornithology, teenager David Wingate, was a member of the team.

The expedition discovered a handful of living Cahows on their nests in burrows on the Castle Harbour islets. By 1962,  a total of 18 nesting pairs had been documented by researchers.

These 36 birds were the only survivors of a species which once numbered in the millions.

Endemic to Bermuda, the Cahow, or Bermuda Petrel (Pterodroma cahow), is a seabird living and feeding on the open ocean.

Boasting a three-foot wingspan and taking its name from the eerie mating call which helped convince early mariners Bermuda was a haunt of devils, the Cahows only visit Castle Harbour for nesting, their breeding habitat reduced to a handful of off-shore islets in the 16th century.

Both the egg and flesh of the Cahow are edible, and since it is utterly fearless of other animals and man, it was virtually exterminated after the island was discovered by explorer Juan De Bermudez in the early 16th century.

Hogs released by Spanish mariners who had hoped to use Bermuda as a mid-Atlantic provisions store during trips to and from the Caribbean and South America proved to be natural predators. The hogs multiplied rapidly and decimated the Cahows on the main island, eating eggs, chicks, and adult birds in their burrows.

By the time the English permanently settled Bermuda in 1612, the Cahow was already nesting on small islands which the pigs could not easily reach.

But Bermuda’s settlement led to the introduction of even more aggressive species including rats, cats and dogs which further depleted the Cahows’ numbers. And the most deadly predator of all proved to be man.

Intensive hunting by the early settlers led to the rapid decline of the remaining Cahow population, which was presumed to be extinct after 1620.

In the 19th century, retired soldier and amateur ornithologist John Tavenier Bartram embarked on an eccentric quest to disprove the accepted wisdom that the Cahow had died out two centuries earlier.

He literally stumbled upon a Cahow specimen — but never realised  he had re-discovered the elusive bird he had spent years trying to find.

On one of the Castle Harbour islands, Bartram found “buried in the sand, dead and pretty well dried up a bird not before known to breed on those Islands. [This] bird was evidently killed whilst sitting on its nest by the falling in of sand and rocks from the top of the hole, was this bird a straggler come here by accident, or do they breed here year after year, I have never heard of them….”

This specimen was later found by David Wingate  in 1953 in a Hamilton antique store which had acquired Bartram’s collection.

In 1906 a live Cahow was found on Castle Island but initially misidentified as a New Zealand petrel. By 1916 scientists had second thoughts, re-classifying the bird as either a Cahow or a close relative.

And a few years after William Beebe argued the fledgling female which struck St. David’s Lighthouse was a Cahow, another body washed ashore on Cooper’s Island — adding further credence to the theory a small breeding population had somehow managed to elude both predators and the march of history.

After the bird’s re-discovery in the 1950s, a conservation programme was started for the Cahow in the 1960s.  Dr. David Wingate — by this point Bermuda’s Chief Conservation Officer — helmed the programme until his retirement in 2000.

The Cahow Recovery Project continues today under the direction of Terrestrial Conservation Officer Jeremy Madeiros with the Department of Conservation Services at the Bermuda Aquarium, Museum & Zoo.

The main objectives of the Cahow Recovery Project are:

• To control and anticipate threats to the Cahow, especially by predators such as rats and marine bird species competing for nesting sites;
• To increase the Cahow breeding population and establish new nesting colonies at secure locations, safe from flooding, erosion, and predation;
• To gain better understanding of the Cahow’s breeding biology and at-sea range through research and technology; and
• To increase public understanding andappreciation of the Cahow as an example of a species rescued from the brink of extinction

“The most urgent continuing threat to the recovery of the Cahow is serious erosion and over-washing of the tiny nesting islets by hurricanes and storms,” said a spokesman for the Cahow Recovery Project.  ”Recent hurricanes have eroded some of these islands to the point where they are no longer stable and can collapse in the next severe storm.

“In addition, these islets are too small to enable the Cahow to fully recover and build up a stable population.”

So the overriding priority for the Cahow Recovery Project in recent years has been to establish the Nonsuch Island nature reserve as a new colony by translocating near-fledged chicks from their natal nest sites on the Castle Harbour islets to a group of artificial nests built at the new colony site.

“There, they are fed every other day and monitored until they fledge out to sea,” said the project spokesman. “Over a five-year period between 2004 and 2008, 105 Cahow chicks were translocated from the tiny eroding nesting islets to nest burrows on Nonsuch. Of these, 103 fledged successfully out to sea.

“In 2009, 15 Cahows from the 2005 and 2006 translocations were recorded in nest burrows on Nonsuch, with at least six pairs of birds recorded together building nests. Although new Cahow pairs normally do not nest successfully until they have been together for two to three years, one pair did produce a chick that became known as ‘Somers’. This chick, named after Admiral Sir George Somers,whose shipwreck on Bermuda 400 years ago led to the island’s permanent settlement, fledged successfully out to sea on June 17, 2009.”

Last month the LookBermuda Educational Media Foundation launched the half-hour documentary “Higher Ground: The Cahow Translocation Project”, chronicling the venture to move chicks from the windswept outlying islands to a new and secure nesting colony on Nonsuch Island.

The story of Dr. Wingate’s role in the Cahow’s battle back from extinction was told by award-winning Bermudian filmmaker Lucinda Spurling in her documentary “Rare Bird” which aired on PBS in the US and won raves at international festivals. But  the new film is the first to focus specifically on the translocation effort led by Jeremey Madeiros.

“Higher Ground: The Cahow Translocation Project”

“I am pleased to lend my support to the work of the LookBermuda Educational Media Foundation,” said Education Minister Dame Jennifer Smith when the film premiered in March. “Their efforts to visually document Bermuda’s unique heritage, history and culture has opened up that world in a way that captures the attention and imagination of our young people and ensures that generations in the future will also understand the importance of sustaining our island home.

“This film on the Cahow, Bermuda’s national bird, will be an asset to schools as they lead students through the local curriculum. I thank the Foundation for this contribution that will help to make teaching and learning in Bermuda even more interesting.”

At the same time the translocation project was winding up in 2009, 12 advanced data tags were fitted onto breeding adult Cahows.

These lightweight monitoring devices allow for daily position fixes to be recorded and stored while the bird is at sea foraging for food for the chick and tracking where individual birds go during the non-breeding period.

The tags, which can record data for up to two years, have already shown that Cahows forage at sea for distances up to several thousand miles to gather food for chicks.

“Although the Cahow remains critically endangered and is one of the rarest seabirds on earth, the Recovery Project has enabled the Cahow to increase its breeding population from 18 nesting pairs producing as few as eight fledged chicks in 1962 to a record 86 nesting pairs producing 47 fledged chicks in 2009,” said the spokesman.

“There is little doubt that the species would have become extinct without a long-term recovery programme and many of the management techniques developed for the Cahow are proving important in other recovery programmes for related seabirds in other countries.”

The Cahow Recovery Project is supported, in part, by the Atlantic Conservation Partnership (ACP) – formerly Friends of the Bermuda Aquarium – a US public charity which active in various Bermuda Aquarium, Museum & Zoo undertakings, including its effort to boost the number of turtles in local waters.

“The Cahow has become a well-known symbol of hope for critically endangered species around the world, and with the first nesting back on Nonsuch Island, the potential for continued recovery has never looked brighter,” said the Recovery Project spokesman.

“Higher Ground: The Cahow Translocation Project” courtesy of the LookBermuda Educational Media Foundation.

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Category: All, Environment