Moa extinction occurred around 1300 CE Although moa skeletons were traditionally reconstructed in an upright position to create impressive height, analysis of their vertebral articulation indicates that they probably carried their heads forward, in the manner of a kiwi.
Although there is no surviving record of what sounds moa made, some idea of their calls can be gained from fossil evidence.The trachea of moa were supported by many small rings of bone known as tracheal rings.Ratites are a basal lineage of birds that are hypothesized to have had a common ancestor 80 million years ago on the Cretaceous southern supercontinent of Gondwana, which subsequently underwent either vicarious speciation as the landmass fragmented, and/or flighted dispersal [Bunce, Worthy 2009].Living members of the ratite lineage include the ostrich of Africa, emu and cassowary of Australia and New Guinea, rhea of South America, and New Zealand kiwi.Gastornis species were very large birds, and have traditionally been considered to be predators of small mammals.
However, several lines of evidence, including the lack of hooked claws in known Gastornis footprints and studies of their beak structure have caused scientists to reinterpret these birds as herbivores that probably fed on tough plant material and seeds.
The nine species of moa were the only wingless birds lacking even the vestigial wings which all other ratites have.
They were the dominant herbivores in New Zealand's forest, shrubland and subalpine ecosystems for thousands of years, and until the arrival of the Māori were hunted only by the Haast's eagle.
Many scientists now consider Diatryma to be so similar to the other species of Gastornis that it should also be included in that genus.
A fifth species, also previously classified in its own genus, is known from China.
Moa were the most significant alternative to mammals on New Zealand, taking the role of the largest dominant herbivores, the same role as large animals such as deer and elephants in other lands.