Casuariidae – Cassowaries

The cassowaries are ratites (flightless birds without a keel on their sternum bone) in the genus Casuarius and are native to the tropical forests of New Guinea, nearby islands, and northeastern Australia. They are in the order Casuariiformes , which has just four surviving members: the three species of cassowary, and the only remaining species of emu. The emus are classified in the family, Dromaiidae, while the cassowaries are all located within the Casuariidae family. There are just three species in this family Casuariidae; 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, occasionally fatal, to dogs and people.

All cassowaries are usually shy birds of the deep forest, adept at disappearing long before a human knows they are there. Even the more accessible southern cassowary of the far north Queensland rain forests is not well understood. All cassowaries have feathers that consist of a shaft and loose barbules. They do not have tail feathers or a preen gland. They have small wings. These are reduced to stiff, keratinous quills, like porcupine quills, with no barbs. A claw is on each second finger. The furcula and coracoid are degenerate, and their palatal bones and sphenoid bones touch each other. These, along with their wedge-shaped body, are thought to be adaptations to ward off vines, thorns, and saw-edged leaves, allowing them to run quickly through the rainforest.

A cassowary’s three-toed feet have sharp claws. The second toe, the inner one in the medial position, sports a dagger-like claw that is 125 millimetres (5 in) long. This claw is particularly fearsome since cassowaries sometimes kick humans and animals with their enormously powerful legs. Cassowaries can run at up to 50 kph through the dense forest., and can jump up to 1.5 metres and they are good swimmers, crossing wide rivers and swimming in the sea.

All three species have horn-like, but soft and spongy crests on their heads, called casques , which are up to 18 cm high. Several purposes for the casques have been proposed. One possibility is that they are secondary sexual characteristics. Other suggestions include that they are used to batter through underbrush, as a weapon for dominance disputes, or as a tool for pushing aside leaf litter during foraging. The latter three are disputed by biologist Andrew Mack, whose personal observation suggests that the casque amplifies deep sounds. However, the earlier article by Crome and Moore says that the birds lower their heads when running …full tilt through the vegetation, brushing saplings aside and occasionally careening into small trees. The casque would help protect the skull from such collisions. Cassowaries live on fallen fruit, and spend a lot of time under trees where seeds the size of golfballs or larger fall from heights of up to 30 metres; the wedge-shaped casque may protect the head by deflecting falling fruit. At least the dwarf cassowary and southern cassowary produce very-low frequency sounds, which may aid in communication in dense rainforest. This ‘boom’ is the lowest known bird call, and is at the lower frequency limit of human hearing.