The cassowaries are ratites, very large flightless birds, in the genus Casuarius native to the tropical forests of New Guinea, nearby islands, and northeastern Australia. There are three extant species recognized today. The most common of these, the Southern Cassowary, is the third tallest and second heaviest living bird, smaller only than the ostrich and emu.
Cassowaries feed mainly on fruit, although all species are truly omnivorous and will take a range of other plant food including shoots, grass seeds, and fungi in addition to invertebrates and small vertebrates. Cassowaries are very shy, but when provoked they are capable of inflicting injuries to dogs and people, although fatalities are extremely rare.
Flightless birds are birds that lack the ability to fly. These species rely on running and/or swimming instead of flying, but evolved from volant ancestors. There are about forty species in existence today, the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguin. Some birds evolved flightlessness in response to the release from predation, for example on oceanic islands, although this is likely not the case for the ratites (the ostrich, emu and cassowary), as evolutionary origins suggest a continental biogeographical providence.
Two key differences between flying and flightless birds are the smaller wing bones of flightless birds and the absent (or greatly reduced) keel on their breastbone. The keel anchors muscles needed for wing movement. Flightless birds also have more feathers than flying birds.
New Zealand has more species of flightless birds (including the kiwis, several species of penguins, and the takahe) than any other country. One reason is that until the arrival of humans roughly a thousand years ago, there were no large land predators in New Zealand; the main predators of flightless birds were larger birds.