The New Zealand bird with a beak like a woodworking tool

Nature · Published 17 October 2026 Swipe more like this →

In short: Imagine a flightless bird the size of a small moa, equipped with a massive downward-curving bill designed to crack through tough prey. This was the adzebill. For over a century, scientists struggled to place this bizarre creature on the tree of life, debating whether it was a relative of the kagu or something entirely unique.

First described by Richard Owen in 1844, the adzebill (genus Aptornis) was initially mistaken for a small species of moa. Its common name derives from its reinforced beak, which resembles an adze—a woodworking tool with a cutting edge perpendicular to the handle. These birds were endemic to New Zealand, with two primary species: the smaller North Island adzebill (Aptornis otidiformis) and the larger South Island adzebill (Aptornis defossor). They were flightless giants, weighing about 18 kilograms (40 lb) and measuring roughly 80 centimetres (31 in) in length. Their wings were notably smaller proportionally than those of the dodo.

Determining the adzebill's ancestry has been a complex puzzle of convergent evolution and genetic analysis. Early theories suggested a link to the kagu of New Caledonia due to their morphological similarities, potentially stemming from a shared Gondwanan ancestor. However, 2011 genetic studies identified them as gruiforms—relatives of cranes and coots. By 2019, more sophisticated phylogenetic methods narrowed their lineage further; while one study linked them to flufftails (Sarothruridae), another used maximum parsimony to suggest a closer relationship to trumpeters (Psophiidae). Most recently, a 2025 paper identified the monotypic family Nesotrochidae as the adzebill's sister taxon.

Ecologically, adzebills were versatile omnivores. Stable isotope analysis of North Island specimens revealed they occupied a higher trophic level than insectivores, likely feeding on large invertebrates, lizards, tuatara, and even small birds. They inhabited New Zealand's lowlands and drier areas but were not as widespread as the moa. Despite their distinctiveness, they succumbed to the same pressures as other megafauna: hunting by the settling Māori—who called the South Island species "ngutu hahau"—and predation of their eggs and hatchlings by Polynesian rats and dogs. They vanished before European explorers arrived.

The adzebill remains a testament to New Zealand's unique evolutionary laboratory, where isolation allowed for radical morphological shifts in flightless lineages.

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