With a wingspan reaching as wide as 3m and huge claws that could crush bone, the Haast's eagle was one of the most fearsome creatures ever to stalk New Zealand's prehistoric wilderness.

The largest eagle known to have existed anywhere, its demise quickly followed that of its much-larger prey, the moa, which was hunted to extinction by early Maori settlers around 1400AD.

Now a top international scientist and Kiwi collaborators hope to shed more light on the lost giant, in an innovative study that could help conserve those endangered predatory birds that remain today.

Professor Andrei Zinoviev, of Tver State University in Russia, will work alongside Dr Paul Scofield of Canterbury Museum and Massey University's Dr Daniel Thomas to digitally reconstruct the powerful muscles, tendons and bones of the eagle's hind limb.

Advertisement

They'll then compare what they find with legs of living eagles that use their hind limbs to tear flesh, and to those that mainly use them to grab prey, just as the Haast's eagle, or Pouakai, likely once did.

By analysing the position and size of the Haast eagle's reconstructed muscles, Zinoviev expected they'd be able to discover the main way it fed, among other rich new insights.

Researchers have maintained the Haast's eagle's population began its slide into extinction when the availability of its key food, the moa, started to dwindle.

Zinoviev noted the bird happened to be the largest terrestrial carnivore around when humans arrived on our shores, more than 700 years ago.

It must have been an intimidating sight for them: the eagle's sheer size, and a body weight comparable to that of a toddler, meant it could strike with a force equivalent to a concrete block falling from the top of an eight-story building.

A comparison of the huge claws of Haast's eagle with those of its close relative the Hieraaetus morphnoides, the
A comparison of the huge claws of Haast's eagle with those of its close relative the Hieraaetus morphnoides, the "little" eagle. Image / Bunce M, Szulkin M, Lerner HRL, Barnes I, Shapiro B, et al

Researchers have theorised the feathered killing machine used its large beak to rip into the internal organs of its prey, whose death would later come from blood loss.

But Zinoviev said its foraging ecology hadn't yet been rigorously demonstrated from skeletal morphology.

"We propose that the eagle used its feet to both seize prey and remove flesh from carcasses, and did not rely on its bill to process carcasses," he said.

Advertisement

"Determining the foraging mode for Haast's eagle has major implications for the accessibility to food, and therefore about the bio-geography of the species and its concomitant vulnerability to extinction."

Professor Andrei Zinoviev with the femur leg of a Haast's eagle. Photo / Supplied
Professor Andrei Zinoviev with the femur leg of a Haast's eagle. Photo / Supplied

The project would ultimately build a "proof-of-concept" case study that could lead to larger studies into other extinct or declining bird groups, including penguins.

"Studies of extinct animal habitats and ecological requirements provide useful information about the reasons for extinction, which can help identify pitfalls for conserving endangered species."

The Haast's eagle

• Its largest claws were as much as 9cm long, making them as large as those of a tiger.

• Most experts agree that it is most likely to have been a more sombre brown or brownish-grey similar to the other very large forest eagles found around the world today.

• Skeletons of Haast's eagles have been found in the drier eastern parts of the South Island, but they probably also occurred in the North Island as well.

• Evidence of talon marks on moa skeletons confirm that they predated on these large birds - prey that weighed up to 200kg. But they also would have targeted other flightless birds - particularly aptornis, weka, takahē, flightless geese and ducks - and potentially even unfortunate humans.

Source: Wingspan National Bird of Prey Centre