Saturday, December 13, 2008

Ancient secret unveiled: Five extinct Hawaiian birds were originally Americans

Hawai'i changes people, and it changes other living things, too—like several native birds that have been living under deep cover for millions of years.

(Image: Rare shot of the now-extinct Kaua'i 'ō'ō by noted naturalist Rob Shallenberger. Source: US Fish and Wildlife Service.)

New DNA work shows that five species of Hawaiian forest birds—long thought to have evolved from islands of the Western Pacific—are actually originally American birds.

It's just that they evolved in the Hawaiian environment to look like island birds, and they've been fooling scientists for more than 200 years.

Tragically, all five species are now extinct. They include the Big Island kioea, and the Hawaii, Moloka'i, O'ahu and Kaua'i species of the 'ō'ō.

“The Hawaiian 'honeyeaters,' five endemic species of recently extinct, nectar-feeding songbirds in the genera Moho and Chaetoptila, looked and acted like Australasian honeyeaters (Meliphagidae), and no taxonomist since their discovery on James Cook's third voyage has classified them as anything else,” wrote scientists Robert C. Fleischer, Helen F. James and Storrs L. Olson, all of the Smithsonian Institution. Their report was published in “Current Biology.”

These birds looked remarkably like the honeyeaters of the Solomons, New Guinea, Bougainville, Australia, New Zealand, Vanuatu, New Caledonia and other islands of the Western Pacific. So everyone who knew birds was convinced that's where they'd come from.

They were classified among the Australiasian honeyeater family, Meliphagidae, although in their own genera: moho for the 'ō'ō and Chaetoptila for the kioea.

The old classifications: Hawai‘i ‘Ō‘ō, Moho nobilis; Moloka‘i ‘Ō‘ō, Moho bishopi; O'ahu ‘Ō‘ō, Moho apicalis; Kaua‘i ‘Ō‘ō, Moho braccatus; Kioea, Chaetoptila angustipluma.

But curious scientists never stop looking, and the team collected DNA samples from museum specimens collected in Hawai'i a century to a century and a half ago, when the birds were still found, thoughthey were rare even then. A book published in 1892 termed Hawai'i “Land of the O-o.”

Author Ash Slivers (a pseudonym), wrote about the birds. A copy of the book is available at Google Books:

“There is a bird called the 'O-o,' that formerly inhabited the islands in considerable humbers. Its plumage is glossy black, except a few feathers under the tail coverts, and a little tuft on each shoulder; these are golden yellow, and from them, in ancient times, royal robes were made. A garment of that kind is now in possession of the Queen, and one is in the Bishop collection. They are valued at incredible sums, as the species is virtually extinct. If you chance to ask a native anything about birds, he is sure to tell you of the 'O-o;' but after that he doesn't know the difference between a bald-headed eagle and a blue-jay,” wrote Slivers, otherwise known as Charles Burnett.

He either knew his birds or had talked to someone who did, since he includes interesting details of the bird's anatomy.

“By a beautiful contrivance of Nature, the O-o carries, at the tip-end of its tongue, a peculiarly equipped, delicate and sensitive brush, by the aid of which it extracts from the calyx of flowers the honey-pools there to be found; and this constitutes largely its main supply of food,” he write, adding that the birds would not turn down a meal of banana or insects.

The DNA evidence studied by Fleischer, James and Olson found that the Hawai'i birds weren't even closely related to those in the Western Pacific. Rather, their nearest relatives were among the waxwings of the Americas, and that their first Hawai'i ancestor had arrived a very long time ago—as much as 14 to 17 million years ago.

While their Mainland ancestors were mainly insect and berry eaters, the Hawai'i birds evolved to take advantage of the nectar in Hawaiian flowers, even evolving specialized split and fringed tongues that assisted in nectar feeding.

Fleischer, James and Olson, with a nod to the traditional scientific terminology, place the Hawaiian birds in their own family, Mohoidae.

Their assessment from genetic data of the time of the birds' ancestor's arrival indicates that it interestingly occurred about the same time as that of the first bird-pollinated plants.

Is there a connection between the arrival of the bird pollinated plants and the nectar sucking birds? Also, why did an American waxwing evolve into something that looked and acted like a Western Pacific honeyeater?

This sort of thing has happened before in nature, and it's something the scientific community calls convergent evolution. That's when very different things evolve to have similar features. Example: Salmon have fins and seals have flippers. One's a fish and one's a mammal, but those swimming devices look quite alike. Another example: wings on bats and birds.

In the words of the scientists who worked on the kioea and the 'ō'ō: “Convergent evolution, the evolution of similar traits in distantly related taxa because of common selective pressures, is illustrated well by nectar-feeding birds, but the morphological, behavioral, and ecological similarity of the mohoids to the Australasian honeyeaters makes them a particularly striking example of the phenomenon.”

(Just to keep things confusing, there's another bird in Hawai'i called the kioea. It's the migratory bristle-thighed curlew. To be clear, that kioea is different from the extinct kioea that's a member of Mohoidae.)

© 2008 Jan W. TenBruggencate

1 comment:

Anonymous said...

Excellent, informative article. Mahalo for the insight.