Hawaii's Vanished Birds
For the National Zoological Park, an artist depicts the diversity of the islands' extinct avian species
- By Adele Conover
- Smithsonian magazine, March 2000, Subscribe
English artist Julian Pindar Hume's pristine scene of a bird kingdom in third-century Maui looks as lush and inviting as Eden. But something is terribly wrong with the picture. The ibises — usually so long and elegant—here have short legs. The gooselike birds have lumpy piano legs like a Galápagos turtle, and seem to have a set of teeth. Clearly they are birds — after all, this group portrait of them hangs in the National Zoological Park's Bird House — but just as clearly, many of them can't fly. Their wings are at best vestigial.
We know that birds had the ability to fly as early as the Jurassic age. Wings were a great survival tool that let them forage and rise above their enemies. So why have these birds given up such an advantage?
Hume's painting is based on the scholarship of Smithsonian Institution avian paleontologists Storrs Olson and Helen James, and it turns out that for these particular birds at that particular time the loss of flight made a lot of evolutionary sense. It was "on purpose" that flightless avians retained into adulthood the features of young birds — big feet and stumpy wings. Their state of neoteny was an adaptation, say Olson and James, to an ecosystem in which there were no mammals or reptiles around ready to eat them. The Hawaiian archipelago was a complete ecosystem, but because it was without the usual lineup of predators and prey, herbivores and scavengers, some birds began taking over these niches themselves.
Flightless rails foraged the dry forest floor like mammals, as likely to rob an egg from a ground-nesting bird as gobble up endemic snails. The owls, which did fly, used their unusually long legs to snatch other birds from the air. Among the analogues for mammal herbivores like sheep were the moa-nalos — a name coined by Olson and James to describe a generic assembly of large, flightless "gooselike ducks," 16-pounders who chomped abundant ferns, aided by toothlike, horny projections on their bills.
There are other evolutionary theories, too. Some scientists believe that because of the steady blast of the trade winds, light, winged birds might have run a high risk of being blown off some of the small windswept islands that make up the northwest part of the archipelago. In that case the flightless ones might have given up wings because they could become "sails," and instead favored heavy legs and feet for ballast.
Still, some Hawaiian birds kept on flying, and maintained the physique that flight required. There was even a flighted top predator, the white-tailed sea eagle, which snagged baby moa-nalos and any other birds it could get its talons on. Unusual island crows wandered about, as ready to munch on fruit as rob a nest or scavenge leftovers. A bunch of pioneer finches — blown from some unknown continent to Hawaii between three million and six million years ago — adapted to "fill in" for absent songbird species in the customary continental landscape. Natural selection reshaped the beaks of pioneer finches in much the same way Darwin's famous finches' were in the Galápagos. There were "woodpeckers," "warblers," "parrots" and "honey creepers" — variations of 50-odd species that make the Galápagos finch tribe's bill adaptations seem run of the mill.
Today most of these birds — airborne and earthbound alike — are extinct. Olson and James say they would probably still be around today if Polynesians had not made their landfall on the islands some 16 centuries ago. The vulnerable flightless mega-ducks, geese and rails were the easiest to catch and so may have been the first to go extinct.
Eventually three-quarters of the versatile finches disappeared, most dramatically because Polynesian kings feathered their robes of office so lavishly. That old terminator habitat destruction, set in motion by the farming methods of Polynesian and Europeans alike, also added to the death toll. So did the introduction of non-native species that competed for resources with, and sometimes preyed on, indigenous birds. The record of many of these birds remains only in a collection of thousands of bones painstakingly reconstructed by Olson and James, then given the appearance of life in artist Hume's portraits.
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