Giant terrestrial birds
The giant terrestrial birds belong to the ratites family, a group of running flightless birds which lacked a wishbone, a bony extension of the sternum to which the powerful muscles necessary for flight are attached. In the current classification, the ratites are part of the palaeognaths group which also includes ostriches, rheas, emus, cassowaries and kiwis.
The giant birds on display here come from two places: Madagascar for the aepyornis, New Zealand for the moas. They were herbivores, but their size made them the dominant animals in their environment. Until the arrival of humans, their only predators were the giant birds of prey that populated the skies of these islands. Among the paleognaths, the females were larger and heavier than the males. This phenomenon, known as inverse sexual dimorphism, was particularly pronounced among the moas and aepyornis.
The gigantism of these species is explained by their insular isolation, the absence of predators and of constraints like shortage of food or harsh climate, etc. The increase in size occurred, in a spectacular way, over several generations.
The moas and the aepyornis reached their adult size between 3 and 9 years of age. Their diet was plant-based: grasses, seeds, mosses, as well as pieces of branches and wood. The crushing of food, and thus digestion, was aided by the presence of gastroliths (i.e. pebbles which they swallowed).
The reasons for the disappearance of these giant birds are uncertain. It occurred around 1,500 years ago, after which records of them cease. The main cause of their extinction is human activity: consumption of their meat and eggs, the introduction of predators (dogs, rats, etc.) and illnesses transmitted by poultry, etc. Changes in climate appear to have played only a minor role.