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
New Guinea flightless rail New Guinea flightless rail The New Guinea flightless rail ("Megacrex inepta"), also known as the Papuan flightless rail, is a species of bird in the family Rallidae, in the monotypic genus "Megacrex". Sometimes however, it was included in "Amaurornis" or "Habroptila", but this is incorrect. It is found in Indonesia and Papua New Guinea. Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical mangrove forests, and subtropical or tropical swamps. It is threatened by habitat loss. "M. inepta" is indeed closely related to "Amaurornis", but not as close as to warrant inclusion therein. Rather, it is