Giant Birds Ate Flightless Moa in New Zealand
Prehistoric Raptor Haast’s Eagle Made Extinct Only 500 Years Ago
Sep 29, 2009
Haast’s Eagle (Harpagornis moorei), a huge predatory bird is believed to have arrived on the South Island of New Zealand about two million years ago.
New Zealand had no predatory animals, and the major grazing animals were species of huge flightless birds, the Moa (Dinornis robustus and Dinornis novaezelandiae).
These were gigantic birds – a full-grown moa could weigh around 250 kilograms (551 pounds).
They had completely lost the ability to fly, and in fact the bones in their upper limbs had atrophied completely, specialist in comparative anatomy at the University of New South Wales, Dr Ken Ashwell told Suite 101.
Dr Ashwell is co-author with Dr Paul Scofield of the Canterbury Museum, New Zealand of a paper describing Haast’s Eagle in the Sepember 2009 Journal of Vertebrate Paleontology
Giant Moa no Match for Predatory Haast’s Eagle
Despite their enormous size, the moa were no match for the islands’ first predator. Dr Ashwell said Haast’s Eagle, which weighed less than a tenth of the moa’s weight was a fierce predator, swooping from the sky and snatching up fledgling moas.
“An adult moa would be too heavy for them, but they could take the young easily,” he said.
The study’s lead author, Dr Scofield, said the study "supports Maori (native New Zealander) mythology of the legendary pouakai or hokioi, a huge bird that could swoop down on people in the mountains and was capable of killing a small child.”
However, Dr Ashwell said he thought the Maori legends “were probably not true”, although he conceded the giant bird could easily attack a small child.
Haast’s Eagle Predator not Scavenger
Despite the Maori legends, paleontologists originally thought that the eagle was only a scavenger, because of its large size compared to modern eagles, around 19 kilograms (40 pounds).
Drs Ashwell and Scofield confirmed it was a true predator, by taking computed axial tomography (CAT/CT) scans of the skeletons.
They used the scans to reconstruct the size of the brain, eyes, ears and spinal cord of this ancient eagle.
These data were compared to values from modern predatory and scavenging birds to determine the habits of the extinct eagle.
The bird’s pelvis had large holes through which nerves for the back legs would have passed. The size of these holes indicate that the bird would have had a powerful grip.
It’s been estimated it would have attacked at speeds up to 80 km/h (50 mph), often seizing its prey's pelvis with the talons of one foot and killing with a blow to the head or neck with the other.
Despite its size and strength, Haast’s Eagle is believed to have a common ancestor with the Australian Little Eagle (Aquila morphnoides), a very small eagle weighing only 815 grams (1.8 pounds).
Humans Led to Giant Eagle and Moa’s Extinctions
When Polynesians arrived on the islands of New Zealand about 2000 years ago, the moa faced another predator, and Haast’s Eagle a competitor.
“The Maoris wouldn’t eat a whole moa, even a small one, but they would certainly enjoy the enormous drumsticks,” Dr Ashwell commented.
Following the Maoris, Europeans colonised the two main islands (North Island and South Island) from the middle of the 16th century, but by then both the moa and Haast’s Eagle had died out.
Between hunting the bird and changing the landscape for agriculture and villages, the Maoris devastated the moa population, and by the 1500s, the moa had died out.
Deprived of its prey, the Haast’s Eagle followed not long after. Dr Ashwell said it is still possible to find enormous skeletal remains in nests in the high mountains of the South Island.
You might also be interested in Three New Australian Dinosaurs Discovered.
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