Birds: Cassowary

Range: northern Australia, New Guinea, and surrounding islands Habitat: tropical forests, wetlands

Flightless feathered family

The cassowary is a large flightless bird most closely related to the emu. Although the emu is taller, the cassowary is the heaviest bird in Australia and the second heaviest in the world after its cousin, the ostrich. It is covered in fluffy, two-quilled black feathers that, from a distance, look like hair. These feathers are not designed for flight but for protection in the cassowary's rain forest habitat, keeping the bird dry and safe from the sharp thorns found on many rain forest plants. Long, strong bare quills hang from the bird's tiny wings. Cassowaries are generally jet black as adults, but the fabulous skin colors on their face and neck vary according to species and location.

Radar or helmet?

All three cassowary species have casques that start to develop on top of their heads at one to two years of age. The casque is made of a firm material that is much like Styrofoam™ and covered with a thick layer of keratin. Although it is quite sturdy, the casque can be squeezed in the middle fairly easily. No one knows for sure why cassowaries have casques. They could reveal a bird’s age or be used as a sort of helmet or shock absorber that protects cassowaries’ heads as they stroll through the rain forest underbrush. The casque could work much like a hornbill’s casque does in helping the bird make sounds. We know that both the southern and dwarf cassowary can produce very low frequency sounds, called booms, which help them communicate through the dense rain forest, so perhaps the casque helps in some way. (Listen to a dwarf cassowary's greeting: you'll hear the low boom and then the sounds of preening.) Females tend to have larger casques than males.

Watch out!

The cassowary is rightfully considered the most dangerous bird in the world! Its three-toed feet have daggerlike claws from the inner toe that are up to 4 inches (10 centimeters) long! It can slice open any predator or potential threat with a single swift kick and can run 31 miles per hour (50 kilometers per hour) through the dense forest underbrush. A cassowary can also jump nearly 7 feet (2 meters) straight up into the air and swim like a champ, so the bird is quite good at fending off threats or escaping danger! That long claw also comes in handy when digging for fallen fruit in the leaf litter.

Important rain forest gardeners

Cassowaries are frugivores that feed on the fruits of several hundred rain forest plants. Because their digestive tracts are relatively short, their droppings contain fruit seeds that are only partially digested. Sometimes these seeds are so large that no other animal can swallow and then deposit them! One test showed that seeds from a rare Australian rain forest tree, Ryparosa sp., were much more likely to sprout after passing through a cassowary’s digestive tract than those that simply fell to the ground on their own. In fact, many plant species require passage through the cassowary's digestive system to be able to sprout!

One is the magic number

Cassowaries are solitary most of the year, living in loosely defined home ranges. If two males meet accidentally, they will stretch their bodies, fluff up their feathers, and rumble at each other until one decides to leave. But if a male meets a female, she can usually make him run merely by stretching a little and staring quietly!

Prom season

Breeding season matches the time of year when fruit is most abundant in the bird's rain forest home: June to October. The solitary female becomes more tolerant of the males as breeding season approaches. The male struts in a circle around the female and calls to her in a series of low booms. She forms a pair bond with a male she selects. The pair stays together until the female is ready to lay eggs, and they will find a nesting site made of a simple scrape in the ground and a few leaves.

Once the female has laid her green eggs, she moves on, leaving the male to incubate the eggs and look after the hatchlings. Like the female emu, she may find and breed with another male and lay another clutch of eggs.

Daddy day care

A male sits on his nest for up to 60 days. Once the brown-and-tan striped chicks hatch, he leads them to his regular feeding grounds, protecting them and teaching them the ways of the world. Youngsters stay with their father for up to 16 months, when he then chases them off to live on their own.

The southern cassowary

Of the three species of cassowary, the southern, or double-wattled, cassowary Casuarius casuarius is the largest and probably most well known. It was first brought from New Guinea to Europe in 1597 by Dutch traders and gets one of its names from the bright red, fleshy pouches of skin (wattles) that hang from its throat. The casque is bladelike and brownish, and the head, neck, and throat are featherless so bright blue skin can be seen. This species lives in the New Guinea lowland rain forests and is slightly less common in northern Queensland, Australia. Many zoos participate in a Species Survival Plan (SSP) for southern cassowaries. The studbook for these cassowaries is held at the Edinburgh Zoo.

The northern cassowary

A bit smaller than its southern cousin, the northern cassowary Casuarius unappendiculatus is the most recent to be discovered by scientists (in 1860) and is probably the most threatened of the three species. Also known as the single-wattled cassowary, this species is found only along the banks or rivers and coastal swampy lowlands of New Guinea. Its casque is larger and more flared than the southern cassowary’s, and the throat skin and wattle are either red or golden, depending on where the cassowary is found.

The dwarf cassowary

The smallest and most colorful of the cassowaries, the dwarf cassowary Casuarius bennetti is 3.3 to 3.6 feet (1 to 1.1 meters) tall and is the only cassowary without wattles. Instead, it has a round purple spot where the wattles would be and bright pink spots on its cheeks. The dwarf cassowary's casque is black, triangular in shape, and is flattened at the back. The head and face are black, the neck is deep blue, and the shoulders are red or violet. This bird lives in the higher elevations of New Guinea, leaving the lowland rain forests to its larger cousins. It is common in New Guinea but is rarely seen in zoos. The San Diego Zoo is lucky to have a female that can be seen by Zoo visitors.

Threats and conservation

There are now fewer southern cassowaries in Australia than there are giant pandas in China. Although none of the three species of cassowary are considered globally threatened, all are suffering from loss of habitat. Much of the Australian rain forest where the southern cassowary is found has now been cleared, and the birds that remain face threats from dogs, feral pigs, hunters, traffic when crossing roads, starvation, and diseases. Hunting and the clearing of forests for farmland affect cassowaries living in New Guinea and its surrounding islands.