Moa Extinction: How New Zealand's Giant Birds Disappeared

The extinction of the moa was the disappearance of New Zealand’s giant flightless birds within about 150 years of the arrival of the first human settlers around AD 1250–1300. All nine known species, some standing more than 3 m tall, were gone by roughly 1400–1450. Their main predator, Haast’s eagle, vanished with them, making this one of the fastest and best-documented human-caused extinctions of large animals.

A land of birds

New Zealand separated from the ancient southern continent of Gondwana more than 80 million years ago. Apart from bats and seals, it had no native land mammals. Birds took over the roles that mammals play elsewhere, and many became large and flightless.

The moa were the most spectacular result. Scientists recognise nine species in six genera, ranging from the bush moa, roughly the size of a turkey, to the giant moa of the genus Dinornis. Unusually, moa had no wings at all, not even the small wing bones that other flightless birds such as emus retain.

DNA studies show that the moa’s closest living relatives are the tinamous of South America, small birds that can fly. This suggests that the moa’s ancestors flew to New Zealand and only later lost the power of flight.

Giants of the forest

The two Dinornis species were among the tallest birds that ever lived. Females were far larger than males, sometimes nearly three times as heavy. This difference was so great that 19th-century naturalists described males and females as separate species until ancient DNA studies in 2003 showed otherwise.

Moa were plant-eaters. Preserved gizzard contents show they browsed on twigs, leaves, seeds and fruits of shrubs and trees. Different species lived in different habitats, from lowland forest to the subalpine zone, and they had few natural enemies.

The only predator able to kill an adult moa was Haast’s eagle (Hieraaetus moorei). It was the largest eagle known, with females weighing perhaps 10–15 kg. It probably struck moa from above with powerful talons, gripping the pelvis and then killing with a blow to the head or neck.

Human arrival and the hunt

When Polynesian voyagers reached New Zealand, as told in the Maori settlement of New Zealand, they found birds that had never faced a ground-hunting mammal. Moa were large, slow to breed and easy to approach.

Archaeological sites of the early settlement period, often called moa-hunter sites, are packed with moa bones. At the mouths of South Island rivers such as the Waitaki and the Wairau, and at Shag River Mouth in Otago, people butchered and cooked moa in large numbers. Some sites contain the remains of thousands of birds, and archaeologist Atholl Anderson has estimated that the largest may represent tens of thousands of moa.

Hunters often took only the best cuts, especially the legs, and left much of the carcass. They also collected eggs, which hit moa populations especially hard because moa laid only one or two large eggs at a time and probably took several years to reach breeding age.

Moa bones were made into fishhooks, pendants and tools, and eggshells were used as water containers. Moa feathers were used in clothing. The birds were thus central to the economy of the first generations of settlers.

How fast was the extinction?

Two scientific studies frame the modern understanding:

• In 2000, Richard Holdaway and Chris Jacomb modelled moa populations against a small founding human population. Their model showed that hunting alone could have wiped out the moa in less than about 100 years, even with only a few hundred settlers.
• In 2014, a team led by Morten Allentoft analysed ancient DNA from hundreds of moa bones. They found that moa populations were large and genetically healthy in the centuries before people arrived. There was no sign of a natural decline from climate change or disease.

Radiocarbon dates from moa bones and moa-hunter sites support a rapid collapse. Most researchers now accept that the last moa died around 1400–1450, at the latest, and in some regions earlier. Estimates of the moa population before human arrival vary widely, from around 150,000 birds to considerably more.

Forest burning added to the pressure. From around 1300, fires cleared large areas of the dry eastern lowlands of the South Island, destroying moa habitat. Dogs and rats brought by the settlers may also have taken eggs and chicks.

A wider wave of extinctions

The moa were not alone. Around the same time New Zealand lost Haast’s eagle, the large flightless, rail-like birds called adzebills, a large flightless goose, a swan, a giant coot and several other bird species. Seal colonies retreated from the North Island and much of the South Island.

The pattern matches other human arrivals on islands across the world, from Madagascar to Hawaii, but New Zealand’s case is unusually clear. Because settlement was so recent and well dated, scientists can compare the arrival of people and the disappearance of animals with great precision.

Moa in Maori memory

By the time Europeans arrived, the moa had been extinct for some three or four centuries, yet they were not forgotten. The word “moa” itself is Polynesian; in other Polynesian languages it refers to the domestic chicken, and the first settlers, who came from the tropical islands described in Polynesian voyaging and the settlement of East Polynesia, seem to have applied it to the giant birds they found.

Maori sayings preserved the memory of the birds. A well-known proverb speaks of something being “lost like the moa”, a phrase used for things gone for ever. Place names containing the word moa are found across the country. Early European collectors also recorded traditions about moa hunting, though by the 19th century these were already distant memories.

Moa bones were found in large numbers by 19th-century settlers clearing swamps and ploughing fields. Some deposits, such as the swamp at Pyramid Valley in North Canterbury, excavated from 1939, held the remains of hundreds of birds that had become trapped in soft ground over thousands of years, long before people arrived.

By the numbers

Rediscovery by science

Europeans learned of the moa from bones. In 1839 the British anatomist Richard Owen examined a fragment of thigh bone sent from New Zealand and concluded that it came from a large flightless bird. Later finds of complete skeletons confirmed his view.

In the 1870s, the geologist Julius von Haast described the giant eagle that now bears his name, from bones found in a swamp at Glenmark in Canterbury. Since then, swamp deposits, caves and dune sites have yielded thousands of moa skeletons, some with preserved skin, feathers and soft tissue.

Myths and facts

• Myth: moa survived into the 19th century. Some early European settlers repeated stories of living moa, and there have been occasional modern claimed sightings, including a widely publicised one in 1993. None has been supported by evidence, and radiocarbon dates show the birds were extinct by the 15th century.
• Myth: climate change, not people, killed the moa. Moa had survived many earlier climate shifts. Their sudden disappearance shortly after human arrival, together with genetic evidence of stable populations, points to hunting and habitat loss.

Timeline

• More than 80 million years ago: Zealandia separates from Gondwana.
• c. 1250–1300: First Polynesian settlers arrive; moa hunting begins.
• c. 1300–1400: Widespread forest fires in the eastern South Island.
• c. 1400–1450: The last moa and Haast’s eagle die out.
• 1839: Richard Owen identifies a moa bone as belonging to a giant bird.
• 1872: Julius von Haast describes Haast’s eagle.
• 2014: Ancient DNA study shows moa populations were stable before human arrival.

Why it matters

The moa extinction shows how quickly a small human population can transform an ecosystem that evolved without people. It has become a key case study for scientists studying extinctions worldwide, and a reminder in New Zealand of the value of the native birds, such as the kiwi and kakapo, that survive today.