Saturday, September 02, 2006

Celestial visions - fairy tern bird

On some tropical islands, the fairy tern is known as the Holy Ghost bird

The fairy tern is a celestial vision: Its silky plumage pure white, its slender wings translucent, its large, black-rimmed eyes the deepest midnight blue. When one hovers above you, all innocent curiosity, you can easily understand why on some tropical islands it is called the Holy Ghost bird.

Fairy terns are small, robin-sized birds with long wings. They have no natural enemies, and generally they are gentle, tame and trusting. They live on remote tropical islands in the Pacific, Indian and South Atlantic Oceans, out-of-the-way spots some people equate with paradise. With their ethereal beauty, the dainty birds fit right in.

I watched them on Bird Island, northernmost of the Seychelle Islands in the Indian Ocean. This 62-acre coral-and-sand outpost set in a turquoise sea is aptly named: Upon it nest in serried ranks nearly a million sooty terns, as well as brown and lesser noddies and about a hundred pairs of fairy terns.

Eccentric breeders, fairy terns are also called love terns. Unlike sooty terns that lay their eggs with synchronous precision during two weeks in early June, they breed at any time of year, at least in the Seychelles. One pair near my cabin was gently amorous in May: The mates sat close together on a branch and alternately preened the fine feathers on each other's faces, the preenee uttering soft, buzzing chirps of pleasure.

The female does not build a nest. Instead she balances her single cream-colored, brown-speckled, slightly spherical egg any place that pleases her at that moment: on a bare branch, swaying palm frond, the jagged tip of a broken palm tree stump, the lintel of a shed, rocks or stones near shore, a piece of driftwood or between the parallel branches of a bush near the sea.

This reproductive high-wire act requires utmost skill and caution when the parents spell each other during the 35-day incubation period. I watched this with worried fascination on Bird Island. One female had laid her egg into a tiny depression on a sloping branch slightly more than thumb-thick. The mate arrived and announced with low croaks and clucks that it was his turn (or hers--the sexes look alike) to incubate the egg. The brooding bird raised itself carefully from the precariously balanced egg and slowly backed down the nest branch. That done, its mate alighted and advanced, step by step, wings held high for balance. Gently, ever so gently, it eased its fluffed breast plumage over the egg, enveloped it with its feathers and settled down to brood.

Such high-risk hatching is like being born on a swinging trapeze, but the chick arrives prepared for danger. It is a little ball of fluffy down with oversized, long-toed feet and an innate and imperative urge to clamp itself instantly to its natal branch. So strong is its grip that should a gust of wind topple the chick, it will hang upside down, then right itself with frantic cheeping and wild flutterings of tiny wings.

A fall means death because the parents do not recognize their chick by sight or call unless it sits precisely where they left it. On one of my early morning rounds on Bird Island, I came upon a fallen chick cheeping piteously on the sand. On a branch above it sat a parent with a beak full of fish, looking puzzled and disconsolate but utterly ignoring its starving offspring. I picked up the famished chick and returned it to its proper spot. It clasped its home branch, and moments later the parent bird began to feed it.

Chicks are voracious, and the parents busy. While noisy sooty terns roam the far seas, fairy terns hunt close to home in offshore waters, usually in late evening or early morning. It is probable that in the soft-gray light of dawn and dusk, a bird's pure- white plumage and translucent wings and tail render it virtually invisible against the softly shining sky.

A hunting fairy tern hovers on rapidly vibrating wings above the sea, dives suddenly and snatches a small fish or squid from the surface without ever getting wet. That is an important precaution because, unlike gulls and other seabirds, its delicate plumage is not waterproof.

Like Atlantic puffins, fairy terns know the neat trick of catching and holding many fish at once without dropping any of them. An adult often returns to its chick with a dozen or more fish, some nearly as long as the chick itself, neatly lined up crosswise in its bill. Maw agape, the youngster swallows the fish headfirst, leaving half out. It digests a part, sits squat--its eyes closed--and swallows convulsively. More fish glides down. Each day, the growing chick can eat about half its weight in food.

For all that, a young fairy tern grows surprisingly slowly. From a roundish ball of brown-gray down, it becomes longer and slimmer and gradually sheds its baby down to reveal the brown-white speckled plumage of a juvenile. After about two months, the chick is fully fledged and ready to fly and hunt on its own.

Fairy terns were once safe on their remote, uninhabited islands scattered throughout the tropical seas. This often changed when ships arrived, for humans, unfortunately, are notoriously careless in paradise. The French claimed the Seychelles in 1742. From their ships came humans and rats, and both prospered and multiplied.


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