Akiapōlāʻau: Hawaiian bird drills wood with its whole body

Researchers led by Alexander Clark, a PhD candidate at the University of Chicago and affiliate of the Field Museum, have published the most detailed anatomical description to date of the ‘akiapōlāʻau (Hemignathus wilsoni), a Hawaiian honeycreeper. The paper appeared in the journal Ornithology on 5 November 2026, according to a Field Museum release distributed via EurekAlert eurekalert.org.

Two beaks in one

The upper and lower parts of the bird's bill differ sharply. The upper bill is long, slender and flexible and is used to probe grubs and caterpillars out of small holes in branches. The lower mandible is short and stout and is used to gouge holes in wood eurekalert.org. Together they let the bird occupy a niche similar to that of woodpeckers, which never reached the Hawaiian islands eurekalert.org.

The authors also describe the bony rostrum of the upper bill and report that it is substantially shorter than the external structure. The bird has proportionally shorter wings than its mainland relatives and a proportionally shorter femur, which parallels the evolution of unrelated woodpeckers eurekalert.org.

Drilling starts at the ankles

The main finding concerns the foot and ankle. The akiapōlāʻau has a proportionally large tendon of a muscle that flexes the ankle, which lets it bring its body downward quickly and powerfully eurekalert.org. Woodpeckers drill mainly with neck muscles, whereas this species, according to the authors, uses the momentum of its whole body, starting with dorsiflexion of the ankles eurekalert.org.

Clark said researchers knew what the birds do but not how their anatomy makes those movements possible eurekalert.org. The data came from measurements of historical museum specimens at three institutions: the UC Berkeley Museum of Vertebrate Zoology, the Burke Museum at the University of Washington, and the Field Museum eurekalert.org.

Status of the species

Experts estimate the wild population at fewer than 2,000 individuals, all living on the northeastern slope of one mountain on the island of Hawaii eurekalert.org. Terrestrial native species of the archipelago have been declining for centuries, and extinction rates have risen in recent decades eurekalert.org.

Clark spent 15 months in Hawaii studying endemic birds. He noted that studying a living species allows researchers to observe the behavior directly, rather than inferring function from fossils eurekalert.org. Paul Banko, a co-author and former USGS researcher, linked the bird's extreme features to intense competition for resources such as caterpillars eurekalert.org.

Hawaiian akiapōlāʻau drills wood with its whole body, from ankles up, a skeletal study of museum specimens finds

Two beaks in one

Drilling starts at the ankles

Status of the species

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