Birds of Australia
The emu has the scientific name of Dromaius novaehollandiae. The emu is Australia's tallest bird. Only the ostrich is taller. The cassowary is only slightly smaller but is much sturdier. All three, together with the rhea and kiwi, are ratites meaning they have no keel to the sternum. All were part of the fauna of Goondwana before the great continent split into its present configuration.
Because there is no keel there is nowhere for wing muscles to attach to and the birds are unable to fly. The wings are vestigial stubs.
Emus have been roaming Australia largely unchanged for about 80 million years. Emus are now found only on the mainland. Two dwarf species from Kangaroo Island and King Island are also extinct.
The emu is endemic to Australia and is highly adaptable. Emus are rarely seen in rainforests or very arid areas, but otherwise they can be found in all habitats from coastal regions to the snowfields. They need to drink every day and will travel great distances if they need too. They can travel from 15 to 25km per day and seem to sense when good rains have fallen. They travel long distances in search of food and water.
The emu stands from 1.6 to 1.9 metres. The plumage is unique as the shaft of each feather supports two complete feathers. The plumage is shaggy with wing, tail and body feathers virtually indistinguishable. The head and neck are covered with fine, black feathers and the skin below is blue/black. The beak is strong, broad and flat. The wings are only vestiges, very small and hidden under the feathers. The spine is strong and flexible. The legs are powerful and equipped with three forward-facing toes on each foot.
Emus range from black to light brown. Most commonly the plumage is grey with black tips. Occasionally an albino is seen. The black tips absorb heat from the sun but the shaggy feathers keep the heat away from the skin. Emus walk at about 1-2 metres per second. This creates enough breeze to remove the absorbed heat. They can forage and walk all day without stress.
Even though they need to drink every day, they have adaptations which help them conserve water. As the bird breathes in, cool air passes through nasal turbinates which are large, highly folded passages. These passages warm the cool air by heat transfer, causing the turbinates to become colder. When the animal breathes out, the warm air condenses into water droplets which are reabsorbed into the body. Emus also pant which increases the amount of water evaporated into the air and helps keep the bird cool. Although this is an effective cooling method, they need to drink regularly to do this.
Emus can swim for extended periods and enjoy the water, seeking out a dam, creek or horse trough on a hot day. They reach 70km per hour for short distances and have a stride of 2.7 metres. Their main form of defence, after flight, is to kick which they do with great accuracy. They can kick in all directions and can break bones and tears muscles without much trouble. The lethal toes will disembowel any dog or dingo silly enough to stray too close.
The female is the larger of the sexes. They vocalise in different ways. The male has a guttural cry and the female 'booms'. Both make grunting sounds. An inflatable neck sac creates the booming, which can be heard up to 2km away.
The omnivorous emu is an opportunist, eating small animals such as mice, insects, fruits, seeds and animal droppings. They love a grain crop and with their big feet, they knock down equally as much as they consume. They also wreak havoc with fences, especially during drought conditions when they are driven to seek food and water. Emus have a high sensitivity to climatic and seasonal conditions. As the days shorten, the appetite of the bird diminishes and hormones are triggered which stimulate the birds to look for a mate. The courtship is lively with the birds doing a lot of drumming. The feathers are fluffed up, bodies bob, dip, duck and grunt. Males may fight for the right to mate with a female. Mating may start just before the rainy season but if the rains are late, the birds will delay breeding.
To mate, the female sits on the ground straddled by the male. Courtship, building a nest and laying the eggs can take up to five months or so. During this time, the pair remain together. Great distances are patrolled by the pair as they defend their territory. Like the cassowary, the emu builds a platform of grass. The pair mate every day or so, the female lays every two to three days. The nest is about 10cm thick and 1 to 2 metres in diameter. A clutch can be anywhere from 8 to 20 eggs. The eggs measure 130 x 90mm and weigh half a kilo. They are a dark bluish-green when fresh but fade in the sun. The shells are thick and composed of layers. Each layer is darker than the one beneath it. This allows for some attractive effects when the eggs are carved.
Once seven or so eggs have been laid, the male goes broody. The female wanders off but may continue to lay eggs in the nest. These may have been fertilised by other males as once a male goes broody the female does not mate with him again. Eventually the female leaves for good but may mate with one or two others and have up to three nests per season particularly during good rainfalls. The male turns the eggs 10 to 12 times a day. Apart from standing to turn the eggs, he will sit for 7 to 8 weeks, living off his body fat and getting moisture from any dew that may fall. He will pull back eggs which roll out of the nest. By the time the chicks hatch, he will have lost 4.5 to 9kg of body fat.
The male is a fantastic father and aggressively protects the chicks. He will adopt any wandering chicks provided they are a similar size to his own. The chicks are cream or grey-coloured with dark brown stripes when first hatched and blend exceptionally well with their environment. Weight gain is a kilo a week in the early stages. They leave the nest after about a week but stay with the male for around six months. The down gives way to dull brown feathers. The birds are fully grown at twelve months old and can breed at 20 months. If chicks hatch they have a 70 to 80% chance of survival. The main predators are dingoes, eagles and feral cats.
Emus are very curious creatures and the aborigines could lure an emu close enough to be hit with a waddi or boomerang by waving a branch in front of them. Tame emus are not above swallowing car keys or parts of cameras.
Emus are attracting more attention as an alternative farming venture. Emu oil has an increasing reputation not just for easing muscle aches and pains, but for being beneficial for all types of skin and skin conditions. The meat is being promoted as a gourmet food and is favoured by those who like a game-type meat. The skins also tan well and can be turned into some very nice items including shoes.