Dromaius novaehollandiae (Emu)
Description: Huge, flighless, three-toed terrestrial birds with long necks and legs.
Adults
They are covered with shaggy, hair like plumage that is brown, often with a grizzled appearance. They have a parting along the dorsal line that is very distinct. The thighs are featherd and the rest of the legs are brown. The neck is bare on the male from about half way up and the skin is blue, the back of the neck and the head are covered with black feathers, the eyes are red brown and the beak blue black. Females have little bare skin and the throat is covered with soft black feathers, the only blue skin visible is on the cheeks and around the ears. The beak is darker and the black throat feathers extend to the base of the neck.
The wings are invisible, hidden beneath the plumage. The body is heavy and compact they have powerful feet and legs. The feet have only three toes.
After moulting the coat can appear almost black for a while but the sun saps the melanin from them.
The females head and neck become darker in the breeding season.
Size: 150-190 cm.
Weight: 30-55 kg.
Senses: The reduced amount of toes on the foot allow emus to run for great distances with little effort, keeping at about 7 km/h, they can also reach high speeds of about 48 km/h for short periods with strides taking 2.7 m each.
Emus are also good swimmers and in exceptional cases they have even been known to cross small costal waters to reach islands.
Habitat: They occupy a large variety of habitats, ranging from woodland and scrub to open country, at any altitude, both on coasts and inland. They avoid areas with less than 600 mm of rain per year, they also aoivd heavily settled zones.
Range: They usually occupy a terriotyr which they mark with booming calls, or grunts if they are male, and remain here throughout the year. However some birds are nomadic and they search great areas for food and water and are always on the move.
Adults have been recorded traveling up to 13.5 km in a day and up to 540 km in just nine months. They generally travel in small groups of all ages, although in the breeding season they travel in pairs.
Distribution: Australia. They have been introduced to Kangaroo Island and Maria Island.
Status: Not globally threatened. Populations are stable. They are thought to have benefited from some of the changes humans have made to their environment, including increased water supplies and fences which exclde predators such as dingos.
At one time 2war2 was declaired by settelers on the emu, this showed that the emu can withstand immense hunting pressure.
Daily Rhythm: They are diurnal, starting their activity soon after sunrise and finishing after sunset, though they are sometimes active on moonlit nights. During the summer and winter, most of the time is spent feeding.
Adult
The daily routine varies slightly from one season to another, in the winter the first hours of the day are dedicated to foraging and moving about in a seemingly aimless manner. Around mid-morning or midday they will make their way towards drinking places, gradually, continuing to feed as they progress. After they have quenched their thirst they spend the rest of the day feeding, usually at a slower rate than before. In summer they spend less time eating, as more food is generally available and the sun becomes very hot at certain parts of the day, at such times they rest int he shade of the trees and drink later in the afternoon. In very high temperatures they will raise their wings, where they have a complex structure of surface veins, this allows heat loss by evaporation.
When they sleep they usually do so on open ground, although in cold weather they prefer to shelter in bushes or grass tussocks. They usually rest in the same spot while they are occupying the same are, when they leave the area, as food becomes scarce they change their resting place to suit their new territory.
Voice: They posses a cleft that is covered frontally by an expandable pouch , which measures some 30 cm in diameter when inflated. This pouch is used to produce a booming sound, they intermittantly drive air through the cleft into the pouch , it then echos in the air-sacs, the sound also has drumming notes which are used in the breeding season.
Outside the breeding season they are usually silent, appart from occasions when they are confronted or when they come across strange objects, in both cases they will grunt and boom. Males tend to grunt more than boom.
Males grunt during the breeding season for three main purposes: as a threat and territorial defense, during the courtship display and before the female lays her eggs.
Both sexes grunt during threat displays but females tend to boom during courtship, to proclaim territory occupation and to threaten others. FEmales also produce a high intensisty booming, this can be heard about 2 km away.
The most characteristic call is a single low, resonant boom, oftemn known as drumming, it is said to resemble an "e-moo e-moo" sound. This sound is made only by females and only during the breeding season, it is thought to attract members of the opposite sex and peaks in intensity when the male begins incubation.
Enemies: Fully grown adults ahve few predators and man is their only real predator. Chicks and eggs are preyed upon by dingos, foxes and birds of prey.
Prey: Omniverous, taking seeds, fruits, shoots (Acacia, Casuarinaceae), grasses (Poaceae), insects (such as grasshoppers, beetles and caterpillars).
Food and Feeding: Plant matter is generally plucked from the plants and only occasionally takne from the ground. Most of the day is spent foraging and they normally stop to drink 1-2 times each day.
The feeding routine usually involves the bird seeking out only highly nutritious food. Whenever it is available they will take the seeds, fruits, flowers and roots of plants, all the parts that have the highest concentration of nutrients. In summer they eat more insects and small vertebrates, and in order to grind down their food in the gizzard they swallow stones, weighing as much as 46 g. They are also known to practice coprophagy, ingesting small amounts of fresh, partly-digested droppings. This is thought to aid them in very dry conditions, as they can retrive lost water and glean the missed nutrients from the droppings.
They spend the day feeding in open spaces, even during very hot periods when other inhabitants of the open plains are resting in the shade and feeding by night. However there is a price to pay for such intense exposure to the sun, they must drink frequently, adults normally drink once a day, twice in the summer. Nevertheless they can can go for several days without drinking during a drought, as long as they can eat succulent plants during this time. Chicks must have access to water on a daily basis and juveniles must drink more frequently than adults.
Prior to incubation, the male will build up a layer of fat, for he will usually not eat of drink at all during the incubation period. In order to avoid dehydrating he goes into a sort of torpor, dropping his temperature by 3-4 degrees C, reducing water loss to a 5th of the normal rate.
Grouping: They generally live alone or in pairs, some groupf of up to nine birds have been counted. They only form groups when they are moving from one area to another or when a place with abundant food and water is found. One place that large and unnatural groups are found, is along the fencelines that humans have errected. these obstruct their progress and they congregate along them.
When seperate groups of emu come together they generally ignor one another. Within each group the bonds are only loose and social interaction is small. Each bird tends to keep to its own space, distancing itself from the others, they normally remain 50-100 m appart, though they will not move more than 1 km away from the group. Antagonistic situations are usually resolved by display, in which the dominant bird will threaten the other: they will simply grunt, stretch their neck out forwards and point their bill downwards. On occasion though the dominant bird will kick, peck and chase their adversary.
When females, and some males, come across strange objects they produce a booming sound repeatedly. with their neck arched and the cervical air-sacs inflated, whilst they circle the object.
Being rather passive and inquisitive birds they are known to follow other species, including humans, possibly just to see what they are up to.
Breeding: They pair in December-January and lay in Febuary-July, with most laying in April or May.
Males will perform a version of the threat display during the time when his mate is laying, or during the nupital dispaly.
Emus are generally pacive creatures but become more aggressive during the breeding season.
Females practice successive polyandry and males take on the full resposibility of incubation and chick care.
Females begin the mating period by drumming, this is thought to attract a male. The male will begin collecting material and building nests within his territory, and the female will gradually join him there. During the courtship display, the paired birds will stand side by side with their heads lowered and their necks bent, they sway from side to side. The male then performs a threat display and when the female sits down he sidles up behind her and grabs hold of her nape with his bill. Finally they copulate, during whichthe male produces squeaks and purring sounds.
The female lays her eggs over a period, leaving a gap of 2-4 days between each.
The pair remain together in the territory for at least 5 months before incubation begins.
Gestation:
Litter Size: 5-15.
Young Description: Juveniles are very dark, particualrly on the head and neck, which can appear barred finely. At 3-5 months the juveniles are about half the adult size and they assume juvenile pluamge rather then the chicks down. After 1 year they are pratically fully developed and look like adults with some juvenile feathers.
Chicks are creamy with brown stripes outling with black stripes on either side, the heads are black speckled. They weigh 440-500 g.
The eggs are dark green, almost black with odd white speckles. They are 130 x 90 mm on average and weigh 450-650 g.
Nest: The nest is normally built in grassland, woodland or heath. The nest is a shallow depression overed in twigs, leaves and grass, the male builds this alone. It is often situated near a bush or a tree, but always in a fairly open area where they male has agood veiw of the surroundings.
Young Care: When the male begins incubating the female will often remain in the area, booming aggressively at all intruders, other females will simply leave the male to incubate alone, seeking another mate and laying more eggs, others will leave and migrate.
During the entrie incubation period, about 8 weeks, the male does not eat, drink or deficate. Although he will never leave the immediate vicinity of the nest and eggs he will get up several times each day to turn the eggs, while the rest of the time he sits tidying the nest, preeing or napping. Once incubation has begun, he will reject the female agressively, she is not permitted to lay anymore eggs, although females have been known to lay 13 days after incubation has begun.
The eggs htch synchronously, never more than 4 days appart. The chicks are precocial and nudifugous, they can walk within 5-24 hours after hatching. When they are 2-7 days old they leave the nest with their parent and within one week they can run and swim competently.
The chicks remain with their father until they are about 5 months old, during this time he is extremely aggressive, and he will often drive away his mate as in the case of any other intruder.
Males that come across wandering chicks will allow them to join his own and cares for them in the same way, however he will only accept them if they are smaller than his own young.
After 5 months the male will loosen the bond he has with his young, he will probably remain with them for about 7-8 months and sometimes as long as 18 months.
Sexual Maturity: 2-3 years. Captive birds have been recorded breeding at just 20 months of age.
Longevity: Captive birds have lived over 10 years.
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