Magazine article International Wildlife

Have Wings, Can't Fly

Magazine article International Wildlife

Have Wings, Can't Fly

Article excerpt

THE ODYSSEY OF THE EGG began on a Madagascar hillside. Washed from its nest by torrential rains, the egg tumbled into a raging stream where its thick shell bounced off rock after rock on a wild ride to the sea. The second leg of the egg's journey was tranquil by comparison, a 7,200-kilometer (4,500-mi.) voyage on the currents of the Indian Ocean to the western shore of Australia. A storm tide rolled t,he egg high on a beach, and it was the slifest of resting places. For as the Earth's oceans retreated from the continents, the broad-expanse of sand became a windblown dune nearly a kilometer inland.

Two thousand years later, three school-children on Christmas holiday made an extraordinary discovery--and carted their treasure to show-and-tell when classes resumed. Thus the elephantbird, a feathered colossus that has been extinct for centuries, leaped into world news in 1993.

Imagine a bird's egg 33 centimeters (13 in.) long and 81 centimeters (32 in. in circumference. An egg so huge that it could hold 12,000 hummingbird eggs, 180 chicken eggs or 7 ostrich eggs. A bird's egg bigger than any dinosaur's egg ever found. Imagine, if you can, the 450-kilogram 1,000-lb. bird that laid that egg.

Imagine that bird flying! In the thirteenth century, Arab traders who had sailed to Madagascar told the Venetian traveler Marco Polo about "gryphon birds' that the natives called rocs. They were, he recounted, "so huge and bulky that one of them can pounce on an elephant and carry it up to a great height in the air."

Well, not really. We know from its 3-meter-tall (10 ft. skeleton that the great elephantbird was built like a steamroller and plodded over the Madagascar landscape on massive legs and feet. But it had only shriveled wings and neither talons nor hooked beak. The roc of Arab fable was an earthbound goliath that ate plants, not pachyderms.

Yet those vestigial wing bones suggest that, once upon a time, elephantbirds (if not elephants) could indeed fly. They eventually lost that power through disuse as they adapted to a terrestrial lifestyle in a place free of predators. For the elephant-bird and many others, it was a choice that worked well--until their paths crossed with humans and the animals they brought with them. Although flightless birds make up fewer than 1 percent of the avian world, they represent one-third of the 75 or more bird species that have become extinct over the past 400 years.

Only a few of the missing, however, were avian absurdities like the elephantbird or the dodo, a giant pigeon slaughtered by famished seafarers on nearby Mauritius Island. At the sublime end of the evolutionary scale, for instance, was a tiny, gilded wren that had the misfortune to encounter a cat named Tibbles. Other flightless birds, among them a colorful gallinule and an owl-faced parrot, cling to the blink with help from conservationists.

Some flightless species, however, have prospered. Seventeen wonderfully varied species of penguins have evolved from airborne ancestors to "fly" in another element: cold Antarctic waters. They share the seas off the tip of South America with flightless steamer ducks, massive waterfowl that chum the surface with wings and feet like a side-wheeler steaming through the water. On the Galapagos Islands, flightless cormorants--the largest members of this cosmopolitan, aquatic family--spread their stunted wings to dry in the equatorial sun. And in tropical South America, no streamside would be complete without hoatzins, fantastic fowl that can swim better than they can fly even though they have long wings.

Then there are the elephantbird's living kin: rheas in South America, the African ostrich, Australia's emu, cassowaries on New Guinea and the kiwis of New Zealand. They thrive, to a greater or lesser degree, in homelands that were joined 130 million years ago in a supercontinent called Gondwanaland--and where they apparently had a common ancestor. …

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