Flightless bird requirement for flightlessness. The kiwi does not exhibit gigantism, along with tinamous, even though they coexisted with the moa and rhea that both exhibit gigantism. This could be the result of different ancestral flighted birds arrival or because of competitive exclusion. The first flightless bird to arrive in each environment utilized the large flightless herbivore or omnivore niche, forcing the later arrivals to remain smaller. In environments where flightless birds are not present, it is possible that after the K/T Boundary there were no niches for them to fill. They were pushed out by other herbivorous mammals. New Zealand had
South Island takahē South Island takahē The takahē ("Porphyrio hochstetteri"), also known as the South Island takahē or notornis, is a flightless bird indigenous to New Zealand, and the largest living member of the rail family. First encountered by Europeans in 1847, just four specimens were collected in the 19th century. After the final bird was captured in 1898, and no more were to be found, the species was presumed extinct. Fifty years later, however, after a carefully planned search, takahē were dramatically rediscovered in 1948 by Geoffrey Orbell in an isolated valley in the South Island's Murchison Mountains. The species is now