The order Struthioniformes comprises the flightless land birds, also known as ratites: Ostriches, Kiwis, Emus, Cassowaries, and Rheas. Being flightless, their breastbone has evolved a different shape from that of their soaring relatives. The breastbone of flying birds has a large keel where the strong wing muscles attach. Having no need for such strong wing muscles, the breastbone of the ratites has become flat like a raft. “Ratis” means “raft” in Latin.
What ratites lack in air speed they make up for in ground speed. Ostriches, the largest birds in the world and found roaming the savannas of Africa, have been clocked at a top speed of 70km/h (42mph).
Except for the kiwi, which is about the size of a chicken, the birds in this order are the largest in the world. Emus are second to ostriches in size, followed by cassowaries. All but the cassowary have feathers on their head and neck, though the feathers on an ostrich’s head are fuzzy and wispy, making them appear bald from a distance. Meanwhile, the cassowary’s bare skin is brightly colored and ornamented. Body plumage among all ratites tends to be black or brown. This order is represented in Africa (ostriches), Australia (emus, cassowaries) Papua New Guinea and nearby islands (cassowaries), South America (rheas), and New Zealand (kiwis).
The diets of ratites vary widely. For example, ostriches eat mostly plant matter with the occasional addition of insects such as locusts, while cassowaries subsist mainly on fruits. Kiwis use their long slender bills to probe for worms and other invertebrates in leaf litter on the forest floor.
The males in this order all participate heavily in rearing the young. In the case of cassowaries, kiwis, and rheas, once the females have laid their eggs, the males take over incubation and rearing of the chicks. The females are not involved. Ostriches and emus, on the other hand, share incubation and chick rearing. Being the largest birds, they produce the largest eggs. Even the diminutive kiwi lays an egg that is up to 1/5 of its own body weight! That would be like a woman giving birth to a 25lb baby!
| Family | Common name | Total number |
| Struthionidae | Ostrich | 1 |
| Rheidae | Rhea | 2 |
| Casuariidae | Cassowary, Emu | 4 |
| Apterygidae | Kiwi | 5 |