This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: There are no woodpeckers on the Hawaiian Islands, but a little yellow bird called the 'akiapōlāʻau (Ah-key-ah-pole-ah-ow) has evolved an unusual beak to drill into branches to find food. A new study in the journal Ornithology provides the most in-depth look yet at this bird's unique anatomy, including its "Swiss Army beak" that looks like two different birds' beaks Frankensteined together.
Researchers learned that this critically endangered bird's beak isn't the only thing that helps it get its meals—its whole body, from its ankles on up, is made for drilling. Their findings also highlight the unique native ecology of the Hawaiian Islands and the urgent need to fight the extinction of their endemic species. "The Aki is unlike every other bird that has ever evolved, and not just in Hawaii—it has features unseen in any birds," says Alexander Clark, a Ph.D. candidate at the University of Chicago, an affiliate of the Field Museum and lead author of the study.
"Its lower bill and its upper bill are distinctly very different from each other." Its upper and lower beaks are so different from one another that they essentially operate as two separate tools, hence the nickname the "Swiss Army knife of the Hawaiian Islands." The upper beak is long, slender and flexible, perfect for extracting grubs and caterpillars from small nooks and holes in branches. The bottom mandible is short, stout and used for gouging holes into wood. Together, these parts allow the Aki to occupy a niche similar to that of woodpeckers, which never made it to the Hawaiian Islands.
"For a bird like the 'akiapōlāʻau to evolve, there had to have been intense competition in the ecosystem," says Paul Banko, coauthor of the study and former researcher at the USGS Pacific Island Ecosystems Research Center in Hawaii. "When the island of Oahu emerged from under the water, there was a relatively large explosion of animal species. This was undoubtedly due to the different species competing for valuable resources, like caterpillars, to feed their young." But even with this understanding of why the Aki developed such extreme features, scientists have been puzzled about how they work.
Many of the Aki's specific anatomical features that allow them to hunt for insects in this way without causing injury to themselves were not obvious to the scientists who study them. "We knew what they're doing, but we didn't quite know anatomically how their body is facilitating those movements. How are they actually doing it?
And now, we have a pretty good idea," says Clark. New findings include a detailed description of the bony rostrum in the upper bill, which the researchers found is substantially shorter than the external structure. The Aki also has proportionally shorter wings than its mainland counterparts and a proportionally shorter femur that mirrors the evolution of unrelated woodpeckers.
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