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Haast's Eagle

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iHaast's Eagle

Image:Giant Haasts eagle attacking New Zealand moa.jpg

Artist's rendition of a Haast's Eagle attacking moa.

Conservation status

Extinct (c. AD 1500)

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Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes
Family:	Accipitridae
Genus:	Harpagornis
Species:	H. moorei

Binomial name

Harpagornis moorei
Haast, 1872

Image:Haastseagleattacksamoa.jpg

Haast's Eagle, Harpagornis moorei, was a massive eagle that once lived on the South Island of New Zealand. It is also known as Harpagornis Eagle. The Haast's Eagle was the largest eagle to have ever lived. It is believed that Māori called it Pouakai; the often-cited name Hokioi (or hakawai) refers to the aerial display of the New Zealand Snipe, specifically the extinct South Island subspecies (Miskelly, 1987). As the hokioi was only known by the loud noise it produced, the Māori assumed it to be a large, powerful bird and were to describe it as a gigantic eagle (the largest flying bird they knew of).

Female Haast's Eagles weighed 10 to 14 kilograms (22 to 30 pounds), and males weighed 9 to 10 kilograms. They had a wingspan of about 2.6 - 3 metres (8-10 feet) at most, which is short for a bird of the Haast's Eagle's weight, but permitted them to hunt in forests. Haast's Eagle is sometimes claimed to be evolving towards flightlessness, but this is not so; rather, it represents a departure from its ancestors' mode of soaring flight towards higher wing loading and maneuverability. The strong legs and massive flight muscles would have enabled the birds to take off with a jumping start from the ground. The tail was almost certainly long (up to 50 cm in females) and broad, further increasing maneuverability and providing additional lift (Brathwaite, 1992). Total length was perhaps up to 140 cm in females, with a standing height of about 3 feet tall or a bit more.
The lower reconstruction (photo of model) gives a rather good impression of the bird's proportions, though the body could be a bit heftier still; the upper one (painting) has wing/tail proportions more typical of an open-country species of eagle.

It preyed on large, flightless birds species including moa up to 15 times its weight (Brathwaite, 1992). It attacked moa at speeds up to 80 kilometres per hour (50 mph), seizing a moa by the pelvis with the talons of one foot and killing it with a blow to the head or neck with a talon of the other foot. In the absence of other large predators or scavengers, a Haast's Eagle could have fed on a single large kill over a number of days.

Early human settlers in New Zealand (Māori arrived about 1000 years ago) also preyed heavily on large, flightless birds and hunted some of them, including all the moa species, to extinction. The Haast's Eagle became extinct around 1400 AD along with its prey. It may also have been hunted itself by humans: a large, fast bird of prey that specialised in hunting large bipeds may have been perceived as a threat by Māori. It was a creature that could kill a moa weighing 180 kg (400 lb), so an adult human may have been a viable prey alternative.

An explorer named Charles Douglas claims in one of his journals that he had an encounter with two raptors of immense size in Landsborough River valley (probably in the 1870s), and shot and ate them (Worthy & Holdaway, 2002); these birds might have been a last remnant species, but this is very unlikely because there had not been suitable prey for a population of Haast's Eagle to maintain itself for about half a millennium at that time, and 19th-century Māori lore was quite adamant that the pouakai was a bird not seen in living memory. Still, Douglas' observations on wildlife are generally trustworthy; a more probable explanation, given that the alleged three-meter wingspan of Douglas' birds is unlikely to have been more than a rough estimate, is that the birds were Eyles' Harrier. This was the largest known harrier, the size of a small eagle, and a generalist predator, and although it is also assumed to have gone extinct in prehistoric times it thus makes a more likely candidate for late survival.

Until recent human colonisation, the only terrestrial mammals found on New Zealand were two species of bat. Free from mammalian competition and predatory threat, birds occupied all positions in the New Zealand animal ecology. Moa filled a grazing niche occupied elsewhere by deer or cattle, and the Haast's Eagle occupied the same niche as carnivorous hunters such as leopards or tigers.

DNA analysis has shown that it is most closely related to the small Little Eagle and Booted Eagle, and not, as previously thought, to the large Wedge-tailed Eagle. In fact, Harpagornis moorei is more closely related to the Little Eagle and Booted Eagle, than these are to other members of the genus Hieraaetus. Thus, Harpagornis moorei should probably be reclassified as Hieraaetus moorei, pending confirmation. H. moorei may have diverged from these small eagles as recently as 700,000 to 1.8 million years ago. Its increase in weight by 10 to 15 times in that period is the greatest and fastest evolutionary increase in weight of any known vertebrate. This was made possible by the presence of large prey and the absence of competition from other large predators.

This bird was first classified by Julius von Haast, who named it Harpagornis moorei after George Henry Moore, the owner of the Glenmark Estate where bones of the bird had been found.

[edit] References

Brathwaite, D. H. (1992): Notes on the weight, flying ability, habitat, and prey of Haast's Eagle (Harpagornis moorei). Notornis 39(4): 239–247. PDF fulltext

Miskelly, C. M. (1987): The identity of the hakawai. Notornis 34(2): 95-116. PDF fulltext

Worthy, Trevor H. & Holdaway, Richard N. (2002): The lost world of the Moa: Prehistoric Life of New Zealand. Indiana University Press, Bloomington. ISBN 0-253-34034-9