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Hieraaetus / Harpagornis
(Grappling hook bird).
Named By: Julius von Haast - 1872.
Classification: Chordata, Aves, Accipitriformes, Accipitridae.
Species: H. moorei (type).
Size: Males about 9-12 kg in weight, females about 10-15 kg in weight. Average wingspan of females about 2.6 meters wide, but some remains suggest a 3 meter wingspan is possible.
Known locations: New Zealand, South Island - including the Hillgrove Formation, and the southern portion of North Island.
Time period: Calabrian of the Pleistocene to the Holocene. Believed to have gone extinct by around the year 1400AD.
Fossil representation: Remains of multiple individuals, though often only partial remains. At least three complete skeletons are known.
In the simplest terms, the Haast's Eagle is in essence, a giant eagle, and one that focused upon hunting only the largest prey available to prehistoric New Zealand: the large flightless moa birds. Isolated remains and estimates of them suggest that the largest Haast’s Eagles could attain a wingspan of up to three meters long, though a two and a half meter wingspan is more easily established from the majority of known remains. Even with the lower estimate however, the Haast’s Eagle still had a wingspan roughly equivalent to today’s largest eagles such as the Steller Sea Eagle (Haliaeetus pelagicus), Wedge-tailed Eagle (Aquila audax) and the Golden Eagle (Aquila chrysaetos). Where the Haast's Eagle really wins in size though is by weight. Most modern eagles, including the females which are usually larger than the males, never exceed nine kilograms in weight when living in the wild (captive kept eagles are not included in case these are overfed). Estimates of male Haast's eagles however range from nine kilograms all the way up to twelve kilograms, while females could weigh as much as fourteen to even fifteen kilograms. This means that the Haast's eagle is probably one of if not the heaviest eagle that we know about to ever take to the air. Because of the extra weight, it is believed that a Haast's eagle would launch itself into the air by jumping up from the ground while flapping.
Haast's Eagle was not a bird that was adapted for long range soaring
over great open distances, the relative shortness of the wingspan is
a clear indication that the Haast's Eagle was adapted for flight
amongst trees and other locations where there was not much room to open
up the wings. By proportion the tail has become enlarged to cover a
larger surface area, something that would help to create lift in the
absence of larger wings. A large tail would also allow for more
stable and more manoeuvrable low speed flight, and would have enabled
Haast's Eagles to have had an exceptional ability for tight turns while
flying amongst trees.
The Haast's Eagle is also credited as having larger jaws than most modern eagles, as well as possessing several long talons on the feet. The talons of the Haast's Eagle are noted as being similar in form to those of the Harpy Eagle (Harpia harpyja). These talons were between forty-nine to sixty-one and a half millimetres long for the front toes while the talon of the hallux (the rear toe that was opposable to the others) was up to one hundred and ten millimetres long. It were these talons that would have been the primary killing weapons of an individual eagle.
The Haast's Eagle was adapted to hunt and kill large prey upon a one on one basis, but the only suitably large prey in New Zealand for such a large predator were the moa. Moa were large flightless birds which are known by several genera, the largest of which of the Dinornis genus (D. robustus and D. novaezelandiae) could grow up to around three and a half meters tall. These birds inhabited the forests that covered New Zealand during the Pleistocene and Holocene, and a possible hunting scenario plays out as so;
A lone Haast's Eagle spots a moa moving though perhaps a less dense growth of trees and then moves itself into position for a strike. From an elevated position the Haast's Eagle begins a downward swoop toward the moa, picking up speed all the while it is making its approach. The moa may be too busy feeding or dinking to notice the approach of the eagle which may also be obscured slightly by the undergrowth. Before the moa can realise the danger the Haast's Eagle sinks its talons into the spine of the moa, which thanks to a combination of the sharp edges driven by the momentum of the heavy eagle travelling at high speed during the point of impact, easily slice and sever the spinal cord bringing instant paralysis. The easiest location for a Haast's Eagle to strike would be the pelvis or the backbone supporting the rib cage since these areas would not be as likely to move as the head and neck. A strike to the spine in these areas would also bring paralysis to the legs, causing the moa to collapse under its own weight. The eagle may have then used a series of strikes from its talons and beak to more quickly subdue the moa, or simply wait for the moa to weaken and die before feeding. The lack of large predators and scavengers on New Zealand meant that a single moa carcass could sustain an eagle for at least several days. The only real threat to a Haast's Eagle at this time would be if another came along and challenged it for territory.
The precise classification of the Haast’s Eagle seems to be up in the air at the time of writing. The Harpagornis genus has been well established for well over a century, and the popularity of this eagle has meant that most people know it as and continue to call it Harpagornis. However, a 2005 DNA study of Haast’s Eagle remains by Lerner and Mindell found that it was closely related to the Little Eagle and the Booted Eagle. Both of these eagles are sometimes re-classified under the Aquila genus, there has been quite a bit of speculation over whether Haast's Eagle should be added to the Aquila genus as a distinct species, or if it should remain in its own genus, Harpagornis. To further confuse matters now, because the Booted and Little Eagle are still classed as belonging to the Hieraaetus by some other authors, Haast’s Eagle is now sometimes referred to as Hieraaetus moorei.
both apex and specialised predators, the future of Haast's Eagles was
certain for as long as there were moa to hunt. However, by
1250-1300AD New Zealand had been settled by the first Māori people,
and this signalled the end for much of the native and specialised
fauna of New Zealand. The first settlers needed to make the land
suitable for long term habitation which meant that vast areas of
forests began to be cleared, destroying the habitat of many animals.
What had a larger impact upon the numbers of Haast's Eagles however
was the active hunting of the moa birds by people. This caused a
significant drop in the numbers of moa which meant that quite suddenly
there was not enough food to support the population of Haast's Eagles
which then began to decline. This continued all the time as the moa
were hunted to extinction, and with the Haast's Eagles unable to
switch to a different food source, they too followed the moa into
Haast's Eagles are usually listed as going extinct at around 1400AD because this was about the time that the moa birds died out. It’s not inconceivable that Haast's Eagles might have survived for a little past this, especially if they had access to a small isolated population of moa that were still untouched. A claim was made by the explorer Charles Edward Douglas however that while he was travelling through the Landsborough River Valley in the 1870s, he shot and ate two raptors of exceptionally large size. Douglas noted that the birds had wingspans equivalent to around three meters and were probably the Pouakai of Maori legend.
However there is some debate about whether Douglas correctly identified these birds. The Maori people at the time insisted that the Pouakai was a bird not seen in living memory, and so far known fossil specimens of Haast’s Eagles confirm that these birds died out long before Douglas made his expedition. Instead, modern interpretation of Douglas’s tale is that he may have actually shot two Eyles' Harriers, a now extinct kind of harrier that was also noted for being unusually large, though not to the extent of the Haast’s Eagle. The reasoning for this is that although Eyles' Harriers succumbed to the same changing conditions as what finished Haast’s Eagles, their more generalist diet means that they may have managed to survive for longer that the more specialist Haast’s Eagles.
- Notes on the weight, flying ability, habitat, and prey of Haast's Eagle (Harpagornis moorei) - D. H. Brathwaite - 1992.
- Late-Pleistocene avifaunas from Cape Wanbrow, Otago, South Island, New Zealand - T. H. Worthy & J. A. Grant-Mackie - 2003.
- Ancient DNA Provides New Insights into the Evolutionary History of New Zealand's Extinct Giant Eagle - Michael Bunce, Marta Szulkin, Heather R. L. Lerner, Ian Barnes, Beth Shapiro, Alan Cooper & Richard N. Holdaway - 2005.