Birds
Cassowary
Casuarius · also called cassowaries
The cassowary looks like a dinosaur that missed the extinction: a two-metre flightless bird with a bony helmet, hair-like black plumage, bare blue skin, red wattles, and a dagger claw on each inner toe. It has a fearsome reputation, mostly earned by people who cornered one. In the rainforest it is something more important — the only animal big enough to swallow and carry the largest fruits, and so the forest’s chief seed-planter.
Overview
Cassowaries are large ratites — kin to the emu, kiwi, ostrich, and extinct moa — living in the rainforests of New Guinea and far north Queensland. There are three species; the southern cassowary is the best known. They eat mostly fallen fruit swallowed whole, several kilograms a day, plus fungi, invertebrates, and carrion.
The dangerous claw
The inner toe of each foot carries a straight claw up to 10 cm long. A cornered or chick-guarding cassowary kicks forward and down, and can inflict deep wounds — hence “the world’s most dangerous bird” — though verified human deaths are very rare and usually involve people chasing or hitting the bird. Feeding cassowaries, which makes them bold, is illegal in Queensland.
Helmet and a sub-bass voice
Every cassowary has a tall casque of keratin over a spongy core; its job is debated — heat loss, sound, and status signalling all have support. The birds also boom at around 23 hertz, near the floor of human hearing and among the lowest bird calls known.
Fathers and forests
The male alone incubates the green eggs for ~50 days without eating and then guards the striped chicks for about nine months. Because the cassowary is the only disperser of the biggest rainforest seeds, dozens of plants depend on it — a true keystone species.
Status
Globally Least Concern, but the Australian population is Endangered with perhaps 4,000 birds, hit by rainforest clearing, road strikes, and dog attacks. New Guinea’s dwarf and northern cassowaries are hunted for meat and plumes.
Cassowary: common questions
Is the cassowary really the world's most dangerous bird?
It is frequently called that, and it is certainly capable of seriously injuring a person, but the reputation is somewhat overstated. A cassowary is large, up to 1.8 metres tall and 60 kilograms, fast, and armed with a long spike-like claw on each inner toe, and when it feels cornered or is defending chicks it can deliver a powerful raking kick that causes deep wounds. However, documented human fatalities are extremely rare, with only a couple of well-verified cases in the past century, both involving people who were cornering, chasing, or trying to hit the bird. Most cassowary encounters end with the bird walking away. The real danger rises sharply when cassowaries are fed by people and lose their wariness, which is why feeding them is illegal in Queensland.
What is the casque on a cassowary's head for?
The tall helmet, or casque, is one of the enduring puzzles of bird biology. It is not solid bone but a shell of keratin over a spongy, air-filled internal structure, and several explanations have support. It appears to work as a thermal window, with blood flow through it helping the bird shed heat in the humid tropics. It may help with sound, either focusing the bird's own very low booming calls or picking up the low-frequency calls of others through the forest. It also grows with age and differs between individuals, so it likely signals maturity and dominance. It may do all of these things at once. What it is almost certainly not is a tool for pushing through vegetation, an old idea with little evidence.
Why is the cassowary important to the rainforest?
The cassowary is the chief long-distance gardener of the forests it lives in. It eats huge quantities of fallen fruit and passes the seeds unharmed, often more than a kilometre from where it fed, deposited in a pile of nutrient-rich dung. For many large-fruited rainforest trees and vines it is the only remaining animal big enough to swallow the fruit whole, so those plants rely on it almost entirely to move their seeds away from the shade and pests around the parent tree. Studies in Queensland have identified dozens of plant species whose regeneration drops where cassowaries have disappeared, which makes the bird a keystone species whose loss would slowly reshape the forest.
How do cassowaries raise their young?
Entirely through the father. A female cassowary holds a large territory overlapping those of several males, mates with a male, lays a clutch of three to five big pale-green eggs in a scrape he has prepared, and then leaves to find another mate, sometimes laying several clutches for different males in a season. The male incubates for about 50 days, barely eating or drinking and losing significant weight, then leads the newly hatched striped chicks around the forest for roughly nine months, showing them food and brooding them at night. He is fiercely protective and will charge dogs, pigs, vehicles, and people that come near the chicks. Once the young are independent he drives them off and the cycle begins again.