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
Flightless cormorant and other small creatures. They feed near the sea floor and no more than 200 metres offshore. The flightless cormorant is the largest extant member of its family, in length and weighing , and its wings are about one-third the size that would be required for a bird of its proportions to fly. The keel on the breastbone, where birds attach the large muscles needed for flight, is also greatly reduced. The flightless cormorants look slightly like a duck, except for their short, stubby wings. The upperparts are blackish and the underparts are brown. The long beak is hooked at