Moa were large to very large birds that lived exclusively in New Zealand. They became extinct less than 600 years ago.
They are classed as a member of the ratite group of birds, which includes the rheas (South America), ostriches (Africa and Europe–Asia), elephant birds (Madagascar), emus and cassowaries (Australia and Papua New Guinea) and kiwi (New Zealand). Ratites (from ratis, Latin for raft) are so named because their sternum (breastbone) is ‘raft-like’, or without a ‘keel’. Ratites are included in the larger group Palaeognathae (literally ‘old mouth’, due to the distinctive shape of their jaw). Palaeognaths are the sister group to all other birds, which are called neognaths. Genetic comparisons suggest that the closest relatives of moa are the flighted tinamous of South America.
Ever since moa were revealed to European scientists in 1840, the question of the bird’s closest relative has been debated. Many people assumed that it was the kiwi because the birds lived in the same area. Some researchers still believe this. However, kiwi have wings and moa did not. Others argue that moa are more closely related to emus and cassowaries.
Certainly, moa are distantly related to the other ratites and have had an independent lineage for millennia. One theory is that the moa ancestor was on the land that became New Zealand when it separated from the supercontinent Gondwana, some 85 million years ago. Another theory is that moa ancestors flew to New Zealand about 60 million years ago, long after New Zealand separated from Australia. Moa evolved to become unlike any other bird, so comparisons are difficult. They differ genetically from other ratites.
Moa were brought to the attention of Western science in 1840 by the naturalist Richard Owen, shortly after he laid eyes on a fragment of moa bone. Within eight years he had named 13 species. Their size and diversity on such a small land was heralded as a natural wonder of the world. Later, more species were accepted, so that in 1907 Walter Rothschild listed 38 in his book Extinct birds.
During the 20th century, work by researchers such as Gilbert Archey, W. R. B. Oliver and Joel Cracraft revised the number of species to be considered valid. Greater understanding of geographical variation, sexual dimorphism (where sexes differ in size), and radiocarbon dating led to the acceptance of fewer species. By 2000, 11 species in six genera were recognised, but this dropped to 10 in 2006, and nine in 2009.
Moa bones make wonderful subjects for DNA studies because in large bones the DNA is protected. Some are only a few hundred years old, and they were often collected from cold places, which preserves the DNA. A moa was one of the first extinct animals from which DNA was taken. In 2001, moa became the first extinct animals for which the entire mitochondrial genome was sequenced.
Scientists can extract ancient DNA from moa bones. They will never be able to recreate a moa, as the DNA exists in small, damaged fragments, and most is mitochondrial DNA, which only contains a tiny amount of the total moa genetic code. But analysis does allow the creation of family trees.
DNA studies and closer examination of moa skeletons have shown that just one species of giant moa (Dinornis species) lived on each of the North and South islands. They have revealed that the really large birds were females, and that the males were usually half the size – it is the most extreme example of reversed sexual dimorphism known among birds.
The nine moa species currently recognised are:
Moa were present in New Zealand on the mainland and the major nearshore islands of Great Barrier, D’Urville, and Stewart Island. These were connected to the mainland during the ice ages, when the sea level was low.
It was once thought that moa were exclusively grass-eating and lived only on grassy plains. It is now accepted that the coastal plains were originally forested, and that these vegetarian birds browsed trees, shrubs and herbs as well as grasses.
Usually, three or four moa species lived together in a habitat that had particular vegetation types:
Giant moa of the Dinornis genus were present in all habitats, from sea level to the subalpine zone, but generally were less common than smaller moa.
There has been much debate as to whether the moa’s browsing gave rise to the small-leaved, highly branched form of many New Zealand plants. Some believe that shrubs evolved spiky twigs to deter moa. Others suggest that the tangled form is an adaptation to the climate, especially strong winds.
Analysis of fossilised excrement and crop and gizzard contents preserved in swamps suggests that moa ate a variety of shrubs and trees. However, moa foraging at heights up to 1,800 metres on a site such as Mt Owen (in north-west Nelson) must have eaten grasses and herbs, since no shrubs or trees existed there above 1,200 metres. Heavy-footed moa are known to have lived in areas rich in loess (fine, wind-blown sediment) and with little vegetation. Each of the six genera of moa had different shaped beaks and gizzard structures, indicating they were adapted to different plants.
Moa were large. Female giant moa (Dinornis genus) were probably over 2 metres tall and heavier than 250 kilograms – significantly more than ostriches or emus. Two extinct birds, the elephant bird (Aepyornis maximus) of Madagascar and ‘the giant duck of doom’ (Dromornis stirtoni) of Miocene Australia, were as tall but bulkier and heavier. Some individuals of Mantell’s moa (Pachyornis geranoides) and the stout-legged moa (Euryapteryx curtus) from the Far North of the North Island were smaller than a large turkey – less than half a metre tall and weighing under 20 kilograms.
Flightless moa were the only birds in the world to lack any vestige of a wing. They had a small bone called the scapulocoracoid, formed from the fused scapula and coracoid. The junction of these two bones is where the humerus of the wing would have been at an earlier stage in evolution.
Moa had rough, furry feathers like a kiwi. The feathers lacked the barbules that usually link the filaments. Little is known about the colour, as feathers have been found only for upland moa. These are dark at the base, lightening to greyish-white at the tip.
Moa had three front-facing toes on each foot, and a small rear toe, often just a spur on the leg. This differs from all other large ratites, which lack a rear toe, and from ostriches, which have just two toes. The moa foot is also distinctive because the tarsus (the scaly part of the leg to which the toes are attached) was very short. In the heavy-footed moa, the breast feathers were barely off the ground.
Moa had small skulls. This is a trait of all ratites, but a 250-kilogram bird would have looked particularly odd with a skull just 23 centimetres long and 12.5 centimetres wide. Their skulls reveal relatively poor eyesight (small orbits), a good sense of smell (enlarged olfactory region), and a very short bill. The bills of different species vary from robust, sharp and pointed to snip branches and flax, to weaker, rounded ones more suited to plucking soft leaves and fruit.
There has been much discussion about the stance of moa. Current wisdom is that like emus, they had a domed back, with the neck rising from the downward slope. The moa’s neck was shorter than any other ratite’s except kiwi’s, and the head was usually held just above the level of the back. Like cassowaries and emus, moa were long birds. Their length was accentuated by their short tarsus. Like emus, they could reach up high to perform threatening displays or gather food.
Little is known about moa breeding. Only about 30 eggs have been found. The largest, attributed to the South Island giant moa (Dinornis robustus), is 24 by 17.8 centimetres, and was found in a Māori burial site at Kaikōura. It is significant as a Māori taonga (treasure) and one of the premier natural history objects of New Zealand. Eggs of other moa species were as small as 12 by 9.1 centimetres, attributed to a stout-legged moa (Euryapteryx curtus).
During the first century or so after their arrival in New Zealand from Polynesia (around 1250–1300 CE), Māori extensively hunted moa as a ready source of food. Hundreds of archaeological sites ranging from single-kill locations to vast middens up to 100 hectares across have shown the great significance of moa in their diet. Moa bones were carved into fish hooks and pendants, and the skins and feathers were made into clothing.
In the archaeological record, Māori use of moa began about 650–700 years ago, but moa remains do not appear in middens later than 1550 CE. There have been a number of claimed historic sightings of the bird, but none held up to scrutiny. Having survived in New Zealand for millennia, with only the giant eagle as a predator, moa were almost certainly extinct by the time of European colonisation, in the early 1800s. Direct hunting and the modification of their habitat led to their rapid demise.
Perhaps because the bird had long disappeared, the name ‘moa’ does not appear to have been widely used by Māori by the time Europeans arrived, and there were few traditional stories about them. The name was first heard by the missionaries William Williams and William Colenso on the East Coast in January 1838, and thereafter became commonly used.
In much of Polynesia domestic fowl are called moa, and large New Zealand moa may have got the name because, as missionary William Colenso suggested, they resembled an immense domestic fowl. The first name recorded for the bird in New Zealand transcribes as ‘movie’, and in 1912 a Māori chief, Urupeni Pūhara, was reported to say that the traditional name was ‘te kura’ (the red bird).
In the early 1830s the trader John W. Harris acquired a 15-centimetre bone fragment. In February 1837 he gave it to a Sydney surgeon, John Rule, with a note that it was from a giant bird called a ‘movie’. Rule took the bone to England, where it was examined by the naturalist Richard Owen in 1839. The following year, Owen proclaimed it to be the femur of a bird, ‘nearly, if not quite, equal in size to an ostrich’, and he appealed for further specimens. Before long they arrived – from William Williams and the naturalist Walter Mantell in particular. Owen coined the genus name Dinornis, meaning ‘prodigious’ or ‘terrible’, and moa came to be regarded as a scientific marvel, of interest to naturalists the world over. Moa bones were regularly exchanged for other items from overseas museums.
The fame of the moa and the fact that its size made it a world-beater gave it the brief status of national symbol briefly in the 19th century. In the 1890s, New Zealand was ‘the land of the moa’, and of 103 entries for a new national coat of arms in 1906–8, 28 included moa. Moa also featured on commercial logos, and in cartoons to represent New Zealand. Its iconic status did not last, however, and was soon replaced by the kiwi.
When in the 1940s the poet Allen Curnow called for a new national literature, he took as his symbol the skeleton of the great moa in the Canterbury Museum:
Taller but not more fallen than I, who come
Bone to his bone, peculiarly New Zealand’s. 1
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Bunce, Michael, and others. ‘Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis.’ Nature 425 (2003): 172–175.
Huynen, Leon, and others. ‘Nuclear DNA sequences detect species limits in ancient moa.’ Nature 425 (2003): 175–178.
Oliver, W. R. B. New Zealand birds. 2nd ed., rev. and enl. Wellington: Reed, 1955.
Worthy, T. H., and R. P. Scofield. 'Twenty-first century advances in knowledge of the biology of moa (Aves: Dinornithiformes): a morphological analysis and diagnosis revised.' New Zealand Journal of Zoology 39 (2010): 87–153.
Worthy, Trevor H., and Richard N. Holdaway. The lost world of the moa: prehistoric life in New Zealand. Christchurch: Canterbury University Press, 2002.