Haast's Eagle

Haast's eagle was one of the largest known true raptors. In length and weight, it was even larger than the largest living vulture (the Andean condor). Another giant bird (not actually an eagle save for in name) more recently and scantily described from the fossil record, Woodward's eagle, which resided in North America, rivaled Haast's eagle in at least the aspect of total length. Female eagles were larger than males. Most estimates place the female Haast's eagles in the range of 10–18 kg (22–40 lb) and males around 9–12 kg (20–26 lb). A comparison with living eagles of the Australasian region resulted in estimated masses in Haast's eagles of 11.5 kg (25 lb) for males and 14 kg (31 lb) for females. One source estimates that the largest females could have weighed more than 16.5 kg (36 lb). The largest extant eagles, none of which are verified to exceed 9 kg (20 lb) in a wild state, are about forty percent smaller in body size than Haast's eagles.

It had a relatively short wingspan for its size. It is estimated that the grown female typically spanned up to 2.6 m (8 ft 6 in), possibly up to 3 m (10 ft) in a few cases. This wingspan is broadly similar to the larger range of female size in some extant eagles: the wedge-tailed eagle (A. audax), golden eagle (A. …

Haast's eagle predominantly preyed on large, flightless bird species, including the moa. Moa would be up to fifteen times the weight of the eagle. Its large beak also could be used to rip into the internal organs of its prey, leading to death by blood loss. Due to the absence of other large predators or kleptoparasites, a Haast's eagle could easily have monopolised a single large kill over a number of days. Its prey, the moa, could weigh up to 200 kg (440 lb). A 2021 analysis showed that, while predatory, the bill of Haast's eagle was functionally closer to that of the Andean condor (Vultur gryphus) than to that of other eagles. This is also supported by historic Māori cave art which depicts Haast's eagle being pale-headed. It also suggests that it deployed feeding tactics more similar to those of vultures after making a kill, plunging its head into the body cavity to devour the vital organs of its prey. This may have been an adaptation to the bird's hunting animals much larger than itself.

Haast named the eagle Harpagornis moorei after George Henry Moore, the owner of the Glenmark Estate, where the bones of the bird were found. The genus name was from the Greek harpax, meaning "grappling hook", and ornis, meaning "bird". In an article in 2025, the biologist Richard Holdaway said he had coined the now-conventional common name Haast's eagle in the early 1990s but on later reflection proposes a more suitable name be Fuller's eagle, after its actual discoverer.