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Extinct New Zealand bird hunted like an eagle and ate like a vulture

The Haast’s eagle had a beak and talons suited for capturing live prey, but its skull was adapted for ripping out organs

Life 1 December 2021

Full size in article - Reconstruction of the Haast?s eagle (Artist: Katrina Kenny)

An artist’s impression of Haast’s eagle

Katrina Kenny

For more than a century, scientists have wondered whether a huge carnivorous bird that went extinct around 600 years ago was more of a predatory eagle or a gut-raiding vulture. Now we finally have the answer: it was both.

The Haast’s eagle, which lived in New Zealand, used its massive talons to hunt and capture prey like an eagle. But instead of gobbling it down whole like modern-day raptors, it ripped the animal’s belly apart and tore out its intestines – the “nicest bits,” says Anneke van Heteren at the Bavarian State Collection of Zoology in Munich, Germany.

“It’s still actively hunting because it’s pulling down such huge prey, but then the feeding is much more of a pulling, like the way a vulture would on an elephant carcass, rather than the way an eagle would gulp down its prey in two or three bites,” van Heteren says.

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The Haast’s eagle (Hieraaetus moorei) weighed up to 15 kilograms, about a third heavier than the largest living eagle, the harpy eagle (Harpia harpyja).

Scientists have long suspected that the bird’s preferred prey was another bird, the land-roaming and now extinct moa, which could weigh up to 200 kg.

To answer the question of whether the Haast’s eagle fed more like a vulture or a true eagle once and for all, van Heteren and her colleagues created digital 3D models of its head and talons. They then compared those to the morphology of five other species of modern eagles and vultures.

With the help of computerised modelling, the scientists determined that, contrary to previous accounts, the beak is actually far more similar to eagles than to carrion feeders. Haast’s eagles could have used their powerful bite to kill large prey such as moas.

But that doesn’t mean it behaved entirely like an eagle, either, van Heteren says. Its neurocranium – the back upper part of the skull – is reminiscent of vultures. The modelling suggests it could bear strains similar to those of the Andean condor (Vultur gryphys), a South American vulture that gulps down internal organs.

The large talons showed remarkable similarities to modern eagles, meaning they were well suited for capturing live prey, even animals far larger and heavier than themselves.

“I thought we were going to get a clear-cut answer, and that that we would find either the one or the other,” van Heteren says. “But instead, we found a puzzle. The fact that [this bird] was hunting like an eagle and then eating like a scavenger surprised me.”

After consuming the internal organs – which are rich with nutrients – and perhaps the muscles, the raptors probably abandoned less appealing tissues such as the skin, bones, and tendons, she says.

A lack of competition meant they could afford to be picky. “When you’re the king of the jungle, basically, you can just eat the nice bits and then move on and catch another one,” says van Heteren.

The Haast’s eagle went extinct in about 1400, when people arrived on the islands and hunted the moa to extinction.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2021.1913

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