The giant eagle was extremely unusual in raptor terms, as it specialised in killing animals considerably larger than itself, as opposed to its contemporaries who kill animals smaller than themselves, because of the need to be able to carry off prey items before anything bigger, or with sharper claws comes along. The giant eagle had no such problems as it was the only raptor to ever be the top predator in its ecosystem, the only real competition came from other aerial predators. The largest terrestrial predator in New Zealand was an ancient reptile called tuatara, weighing in at just a couple of pounds, it preferred to feast on insects and other small invertebrates.

The giant eagle killed a range of flightless birds, ranging from small moas weighing in at just a couple of pounds, all the way to one of the largest birds to ever walk the Earth, the giant moa, a ten foot high, 450Ib, lumbering version of the ostrich. Like other raptors, the giant eagle was not averse to feasting on carrion or taking advantage of any trapped animals. The eagle’s hunting strategy was to position itself on a high perch, scan the ground for any suitable prey. Once, spotted it would leap into the air, then swoop down at a speed of roughly 50mph. If tackling a large flightless bird, it would aim for the bird’s hindquarters; the resulting strike would be the equivalent of a concrete block dropped from the top of an eight storey building, inflicting deep wounds and massive internal bleeding. The moa would probably have died quickly from shock or loss of blood. Fossils have been found of giant moas with huge gashes and punctures on their pelvis, they also show how the eagle would have utilised its long beak to gain access to the carcass. The giant eagle’s long legs ensured that it would always be well cushioned against any impact, thus preventing it from coming to harm. Due to the lack of competition, the giant eagle could remain at a kill site for days on end, gradually devouring its meal.

Mankind first discovered New Zealand, around 800 years ago, for us it was one of the last habitable landmasses to be discovered, and what a place to discover, a land of evolutionary oddities, a land ruled by birds rather than mammals. The earliest Maori settlers left no direct evidence that they were preyed upon by the giant eagle, all we have are a few mythic clues buried in their folklore. But it seems likely; imagine a person walking through the dense forest. To a giant eagle, the person looks odd, but is still a two legged animal, thus making them fair game. If a giant eagle was capable of taking down a 400Ib plus Moa, then it would have experienced little problem in tackling a person.

The existence of the giant eagle may explain why some of New Zealand’s surviving flightless birds, such as the kiwi and the kakapo live nocturnal lives. The giant eagle was a diurnal, apex predator, capable of tackling any species of flightless bird. The kiwi and kakapo among others adopted a nocturnal existence as the best way to hide from the giant avian predator. So, even today the eagle’s ghost lingers, six centuries after its extinction. Adaptation to nocturnal living is a strategy used throughout the history of life, by many creatures to avoid predators. During the age of the dinosaurs, our ancestors, the early Mammals took to living in the dark, in order to escape the detection of the giant reptiles.

At this time, nothing is known about the reproductive strategy of the giant eagle, due to the fact that no eggs or chicks have ever been found. But looking at modern eagles, may give us at least some insight. Most modern eagles lay two or three eggs in a huge nest built in a huge tree with a massive canopy, or high up on a rock ledge. With eagle chicks, the fight to survive is very competitive, and usually the weakest ones end up succumbing to death.

All of the fossils found thus far, have been recovered from the South Island, and analysis of the environment suggest that the giant eagle inhabited dense forest, shrub lands and grasslands on river floodplains. It is thought that the giant eagle was capable of living of up to 20 years; they may have paired for life, occupying vast territories ranging up to 150 square miles.