The moa were eleven species (in six genera) of flightless birds endemic to New Zealand. The two largest species, Dinornis robustus and Dinornis novaezelandiae, reached about 3.7 m (12 ft) in height with neck outstretched, and weighed about 230 kg (510 lb).
Moa are members of the order Struthioniformes (or ratites) although some sources also recognise these as the separate order Dinornithiformes. The eleven species of moa are the only wingless birds, lacking even the vestigial wings which all other ratites have. They were the dominant herbivores in New Zealand forest, shrubland and subalpine ecosystems for thousands of years, and until the arrival of the Māori were hunted only by the Haast's Eagle. All species are generally believed to have become extinct by 1500 AD, mainly due to hunting by Māori.
The moa's only predator was the massive Haast's Eagle—until the arrival of human settlers.
The Māori arrived sometime before A.D. 1300, and all moa genera were soon driven to extinction by hunting and, to a lesser extent, forest clearance. By about A.D. 1400 all moa are generally thought to have become extinct, along with the Haast's Eagle which had relied on them for food. Recent research using carbon-14 dating of middens strongly suggests that this took less than a hundred years; rather than the period of exploitation lasting several hundred years which had been earlier believed.
Some authors have speculated that a few Megalapteryx didinus may have persisted in remote corners of New Zealand until the 18th and even 19th centuries, but the view is not widely accepted. Some Māori hunters claimed to be in pursuit of the moa as late as the 1770s. Whalers and sealers recalled seeing monstrous birds along the coast of the South Island, and in the 1820s a man named George Pauley made an unverified claim of seeing a moa in the Otago Region of New Zealand. An expedition in the 1850s under Lieutenant A. Impey reported two Emu-like birds on a hillside, on the South Island, and an 1861 story from the Nelson Examiner told of three-toed footprints measuring 36 centimetres (14 in) between Takaka and Riwaka, found by a surveying party, and finally in 1878 the Otago Witness published an account from a farmer and his shepherd.
Though scientists agree there is no doubt that moa are extinct, there has been occasional speculation—since at least the late 1800s, and as recently as 2008—that some moa may still exist, particularly the rugged wilderness of South Westland and Fiordland. Cryptozoologists and others reputedly continue to search for them, but their claims and supporting evidence (such as of purported Moa footprints or blurry photos) have earned little attention from mainstream experts, and are widely considered pseudoscientific.
Experts contend that moa survival is extremely unlikely, since this would involve the ground-dwelling birds living unnoticed in a region visited often by hunters and hikers.
While the rediscovery of the Takahē in 1948 (after none had been seen since 1898), showed that rare birds may exist undiscovered for a long time, the Takahē was rediscovered after its tracks were identified—yet no reliable evidence of moa tracks has ever been found. The Takahē is also a much smaller bird.
A 2010 episode of the paranormal television program Destination Truth featured a search for the giant moa.