The largest eagle to have ever lived

The Haast Eagle, Harpagornis moorei, was the largest eagle to have ever lived.  Sadly very few humans had the chance to appreciate its awe inspiring power and magnificence, as it became extinct within a couple of hundred years of the arrival of the first people to the islands of New Zealand. Those people that may have come into contact with this eagle would have been filled with equal parts of admiration and fear, as the eagle would likely not have given it a second thought on whether to attack and eat these bony stringy new arrivals to its world.

Using skeletal remains and scaling up from existing forest eagles, Haast eagle would have weighed at least 13kg! The largest existing eagle, the Harpy Eagle, typically tops the scales at 9kg, while the Crowned Eagle, impressive as it is, is a lightweight by comparison at nearly 5kg (given weights of the larger female). While the wingspan measurements of 2.5 to 3 meters are similar to long-winged eagles such as wedge-tailed eagle, golden eagle, and stellar sea-eagle, the forest-raptor composition of short wings and massive bulk was unrivaled. The foot mass and structures for powerful tendons indicate great strength, suggesting this eagle had ample capacity to subdue the largest of prey - indeed there are hip bones of Giant Moa with talon holes matching those of the Haast Eagle. Though prey would more typically have been smaller birds; such as the smaller species of moas, flightless geese, rails, and takahe - prey that it could kill instantly (avoiding potential injury) and carry off to devour in peace or carry to the nest site.

The nearest common ancestor to this behemoth is the petite Little Eagle of Australia.  Using genetic markers as measures of time, it is estimated that the Haast Eagle scaled up from a diminutive eagle about 1kg in size to a 15kg monster over just 0.7 - 1.8 million years.  This is one of the most extreme and rapid examples of island gigantism you could find - arising because of a completely unchallenged fitness landscape involving large and flightless bird prey in forested and mountainous environments.

Size of a Wedge-tailed Eagle [C] and male Haast Eagle [D]. from Brathwaite 1992.

Life sized silhouette at Wingspan National Bird of Prey Centre. Photo Claire Raisin

A Haast Eagle being mobbed by Karearea in the southern high country. Tennison & Martinson 2006.

display piece at Te Papa museum

Pre-human ecology of New Zealand was one of the last large untouched landmasses on Earth, a remote south Pacific paradise of birds. The only mammals here were three species of bat, and so all of the bird and reptile species that arrived in Zealandia after the drowning of Tasmantis 23 mya were free to develop quirky characteristics. Most influential of all in this ecosystem of eagle food were the 12 or so species of Moa, ratites that occupied every corner of the main islands; from the smaller Upland Moa weighing 30kg, to the enormous South Island Giant Moa Dinornis robustus, over 200kg and exceeded in size only by the Giant Elephant Bird of Madagascar. This diversity of moa: grazers of the alpine grasslands and browsers of the forest interior, were accompanied by a whole assortment of other large flightless birds now extinct. Even the tiniest birds, a genus of Wrens unique to New Zealand, included some species that were flightless, which would have lived scurrying about the forest canopy searching for all manner of small insects.

Relative size of four species 1-N.I. Giant, 2-Eastern, 3-Little Bush, and 4. S.I. Giant Moa. 

Upland Moa, South Island Goose, and Stout Legged Wren. Tennison & Martinson 2006.

Three diurnal raptors inhabited this lost world, bird predators in a bird paradise. While the Haast Eagle was a giant, another unique and notable predator was the Eyles Harrier.  This was the middle-class predator.  Island gigantism and the ‘forest raptor’ transformation took hold of this Harrier too so that, with short wings, long tail, and strong sturdy legs and feet, Eyles Harrier hunted these forests in much the same way as a large goshawk or hawk-eagle might - far removed from the lifestyle of the swamp harrier that quarters open country farmland these days. The smallest raptor is the only one that managed to persist through the extinction events that followed human arrival.  This is also one of the quirky examples of unique NZ. The Karearea is a short-winged falcon, and a pursuit predator of note. It is much admired as the head-piece of the 20 dollar note, and with a rewarding publicity boost, managed to win the top spot in the 2012 bird of the year.  The existence of these rapacious predators may have pushed some of New Zealands most iconic existing birds, the Kakapo, and Kiwi, to nocturnal lives.

The drama of talons from the skies kept all the birdlife on edge, the isolation and eternal absence of terrestrial teeth-and-fur set the stage for a great fall of this easy living menagerie. The sudden arrival of Polynesian settles – who soon became uniquely Maori - made landfall with an effective toolkit and deftly knowledge.  Moa were most likely completely nonchalant about another bipedal inhabitant to share the islands with, making them simple to walk up to and bop them on the head for a great chicken roast. Stone weapons and fire were used with shocking effectiveness, clearing land, burning forest and cooking all the beasts that roamed.  Some midden sites dating to moa-hunting periods are vast collection containing thousands of moas and many unopened ovens and articulated remains suggest huge wastage in the early days of plenty.  The Maori people arrived sometime around 1200AD, and moa do not appear in middens after 1550AD.

This great eagle would have suffered at the loss of so much of its prey base at the hands of this profligate competitor.  Haast eagle was likely to have failed to discern one bipedal animal from another, and looked upon humans as a scrawny stringy version of its typical moa prey especially if donned with a feather cloak . If the eagle typically hunted 100kg moa, then an adult person much less a child, would have been easy game. A few of the skeletal remains of Haast eagle have been found in Maori middens, so while the loss of its prey due to competition was a major contributor, the Maori appear also to have hunted and eaten them.  Whether this is an act of a pre-emptive strike to protect family and hunting parties, of selfish elimination of a competitor, or prestige and bravery where the mana of the eagle could have been absorbed by consumption.

The Haast Eagle goes by one or other Maori names, Te Pouakai and Te Hokioi.  Two Maori legends legends exemplify its lost magnificence.

Illustration by Colin Edgerley in New Zealand Geographic. 

Te Pouakai

Pouakai was a fabled flying beast which would snatch unwary children who ventured out too early in the mornings or stayed away from their homes late in the evenings. These stories are part of the tribal lore of most Taranaki, Tainui and Whanganui tribes. One such story was told to John White in the late 1880s.
For some years one of the huge creatures had been terrorising the people of an inland village in the hills north-east of Taranaki mountain. Although its wings made a loud noise as it flew, it was so fast that several people had been caught and killed.
A visiting chief, Te Hauotawera, saw how afraid the people were and offered to destroy the beast, provided a group of men would follow his instructions. This was agreed and the party went out one dark night to a large pool near the lair of the taniwha and covered it with a network of manuka saplings and large fern fronds. The men then hid under the network with long sharp spears.
When daylight came Te Hauotawera stepped out of hiding to taunt the man-killer and lure him into an attack. Before long the sound of huge wings could be heard and the brave young chief managed to get under the sapling network just as the huge talons reached for him.
The hidden men thrust their spears upwards and after a long struggle the pouakai lay dead.

       - excerpt Taranaki Daily Times, Fairfax NZ News

Te Hokioi Travels to the Heavens

Te Hokioi, was seen by our ancestors. We (of the present day) have not seen it – that bird has disappeared now-a-days. The statement of our ancestor was that it was a powerful bird, a very powerful bird. It was a very large hawk. Its resting place was on the top of mountains; it did not rest on the plains. On the days in which it was on the wing our ancestors saw it; it was not seen every day as its abiding place was on the mountains. Its colour was red and black and white. It was a bird of (black) feathers, tinged with yellow and green; it had a bunch of red feathers on top of its head. It was a large bird, as large as a Moa. Its rival was the hawk. The hawk said it could reach the heavens; Te Hokioi said it could reach the heavens; there was contention between them. The hokioi said to the hawk, “what shall be your sign?” The hawk replied, “kei”. Then the hawk asked, “what is to be your sign?” The hokioi replied, “hokioi-hokioi-hu-u.” These were their words. They then flew and approached the heavens. The winds and the clouds came. The hawk called out “kei” and descended, it could go no further on account of the winds and the clouds, but the hokioi disappeared into the heavens.

     - from Riley, M. 2001. Maori Bird Lore. Viking Sevenseas NZ Ltd.

REFERENCES

Anderson, A. 1989. Prodigious Birds: moa and moa-hunting in prehistoric New Zealand.

Brathwaite, DH. 1992. Notes on the weight, flying ability, habitat, and prey of Haasts Eagle. Notornis 39(4).

Bunce M, Szulkin M, Lerner HRL, Barnes I, Shapiro B, et al. (2005) Ancient DNA Provides New Insights into the Evolutionary History of New Zealand's Extinct Giant Eagle. PLoS Biol 3(1):

Campbell, Hamish; Gerard Hutching (2007). In Search of Ancient New Zealand. North Shore, New Zealand: Penguin Books. pp. 166–167.

Holdaway, R. N. 1991. Systematics and Palaeobiology of Haast’s Eagle Harpagornis moorei Haast 1872. PhD thesis Christchurch: University of Canterbury

Lundmark, C. 2005. Evolutions fast lane. Bioscience 55(2).

Tennison, A., and Martinson, P. 2006. Extinct birds of New Zealand. Te Papa Press, Wellington, New Zealand