Southern cassowry (left) and emu (right). Australia's two large flightless bird species.
What is a ratite?
Ratities are an order of flightless birds, most of them large in size: Ostriches, rheas, emus, cassowaries, and kiwis. Those found in Australia are the single living species of emu, and one of the three living species of cassowary.
Birds diverged from dinosaurs at least 150 million years ago. The ancestors of modern bird species are the only known dinosaurs to have survived the mass extinction event 65.5 million years ago, caused mostly or totally by a large comet or asteroid smashing into what is today Mexico’s Yucatan Peninsula.
Modern birds are divided into two taxonomic superorders, Neognathae and Paleognathae. As you might be able to tell by the prefixes on the words, Paleognathae is considered an older and more primitive group, and Neognathae represents more modern bird species.
Only 60 species belong to Paleognathae, and the other group contains the rest of the nearly 10,000 known bird species. Paleognathae is divided into two orders, the tinamous and the ratites. There are thirteen ratite species, two of which live in Australia.
The two species of ostrich in Africa are the tallest and heaviest birds in the world. Emus are the third-tallest, and the fifth-heaviest. The third-heaviest is the southern cassowary. Fourth-heaviest is the northern cassowary, which lives on the island of New Guinea.
There were once five subspecies of emu, although two went extinct during the 19th century. Those that are no longer with us lived on Tasmania and King Island, and with their demise the emus that remain are native only to Australia’s mainland. They are found over most of the continent, except for the most arid areas, dense forests, and areas heavily populated by humans.
Emus reach up to 75 inches (191 cm) in height, although more commonly are 55 to 65 inches (140 to 165 cm). Average weight is 70 to 80 lbs (32 to 36 kg), and the largest are up to 130 lbs (59 kg). Females are usually larger than males.
They have very strong legs, and besides being able to run 30 mph (50 km per hour), they use their clawed feet for defense, although almost never attack humans. In the wild they will kick to defend themselves against Australia’s wild dogs, the dingoes. This doesn’t work however on Australia’s largest bird of prey, the wedge-tailed eagle, which hunts full-grown emus.
Emus are commercially farmed in Australia, the USA, and some other countries, primarily for meat, leather, oil, and eggs. Emu eggs are famous for being a brilliant dark green color (shown further below).
There was once a second emu species, which went extinct during the 19th century. It lived on Kangaroo Island, near the coast of South Australia.
Other ratites that went extinct during the current Holocene Epoch, which is about 11,700 years ago to the present, include the giant moa, which inhabited New Zealand until just a few hundred years ago, and the massive elephant birds of Madagascar, which went kaput about 1,000 years ago. Not all scientists, however, agree that elephant birds should be classified as ratites.
A male southern cassowary caring for his offspring. This is in the Artis Zoo in Amersterdam, Netherlands.
The third-most massive bird in the world after the two species of ostrich is the southern cassowary. It’s not as tall as the emu, but is heavier on average. These large birds are black, with blue heads and necks, two red wattles, and a fin-like protrusion on top of the head, called a casque, which is brown in color.
The feet of these birds have large dangerous claws on each inner toe, which can be nearly 5 inches (12 cm) in length apiece. They will kick to defend themselves, and can kill adult humans and other threats, such as dingoes. They are considered the most dangerous birds in the world to humans.
These birds reach 50 to 75 inches (127 to 191 cm) in height, and on average are shorter than emus. Weight for males is often 65 to 75 lbs (30 to 34 kg), and females average 130 lbs (59 kg), and some exceed 150 lbs (68 kg). On average they are heavier than emus, and of all bird species, only ostriches are heavier.
They live in tropical rainforests along the northeast coast of Queensland’s Cape York Peninsula in Australia, and also on the island of New Guinea and a few nearby Indonesian islands.
They eat fruit that has fallen to the forest floor, fungi, insects, and small vertebrates. They are solitary animals, forming pairs during the breeding season each year. Males build nests on the ground, and also incubate the eggs and raise the chicks. Each nest has three or four greenish eggs.
More live outside Australia than within. In Australia, it is estimated that there are fewer than 3,000 of these birds left, and they are listed as vulnerable, which is one level better than endangered.
This is the standard color for emu eggs, which average 5.3 x 3.5 inches (13.4 x 9 cm) in size.