The Emu (Dromaius novaehollandiae) is the second largest bird in the world, with adults' heights ranging between 4.9 and 6.2 feet (150-190 centimeters), and their beak-to-tail lengths ranging between 4.6 and 5.4 feet (139-164 centimeters). Females of this species are usually larger than the males. The shaggy appearance of the bird is due to its double-shafted brown feathers. Emus are flightless birds with a small wingspan and a feather structure which does not favour flying. The sole purpose of their vestigial wings and feathers are thus to provide insulation from extreme weather conditions. Their feet possess three toes with small pads underneath them to aid in running over harsh terrain. Their long legs and highly developed pelvic limb musculature allows them to run at extremely high speeds, which can reach up to 30 miles per hour (48 kilometers per hour). This agility, together with their sharp claws, eyesight, and hearing abilities, allows the birds to defend themselves effectively. The body of the emu is covered with grey-brown plumage, with the pale blue color of their skin peeking through around the neck region.
Emus have an omnivorous diet pattern, consisting of plant foods such as flowers, seeds, and fruits, as well as insects. A wide variety of insects such as grasshoppers, beetles, caterpillars, crickets, moths, and ants are all consumed by emus. Like ostriches, emus also swallow stones and pebbles to aid in digestion. An emu can swallow stones of up to 1.6 ounces (45 grams) and can hold up to 1.5 pounds (700 grams) of stone in their digestive system at any single point of time. When in captivity, these birds have been observed to swallow marbles, nuts, bolts, jewelry, and other unusual items. Emus prefer to live in regions with sufficient water and food, and will travel long distances, up to 7.5 to 9.3 miles (12-15 kilometers) a day, when their food resources become scarce.
Habitat and Range
Emus occur all throughout mainland Australia across a wide variety of habitats, ranging from coastal regions to high altitude areas. They prefer to live in regions with sustainable sources of food and water such as open forests, woody areas, wetlands, and farms. The savannah grasslands and sclerophyll forests of Australia have especially high populations of these unique birds.
Emus are diurnal creatures who settle down to rest after sunset and sleep the rest of the night. They spend the daytime hours in such activities as foraging, cleaning their feathers, and dust bathing, interspersed with occasional periods of rest. Unique sounds are produced by these birds, predominantly "booming" by females and "grunting" by males. The booming sounds are produced during times of courtship, and serve as threats to rivals competing for territory and mates. An inflatable throat pouch is responsible for producing these sounds, and their pitches vary from a high intensity boom that can be heard from a distance of 1.2 miles (2 kilometers) to a lower one used during courtship and nesting periods. Grunting sounds are produced by the males during territorial defense, courtship, and nesting. Emus pant during the hot season to release heat and, during cold weather, their multi-folded nasal passages warm the incoming air that reaches the lungs. Emus are able to swim, but typically do so only during emergency situations like flooding or when rivers bar their access into better habitats.
During the summer months of November to January, the male and female emus pair up for a period of about five months. Mating occurs during the months from April to June, when the males experience an increase in testosterone and luteinizing hormone levels, leading to a doubling in the sizes of their testicles. Both male and female emus also grow in size during this period. Males build nests on semi-hollow regions in the ground, which are almost flat in structure. The nesting area is selected in such a manner as to provide a clear view of the surroundings to detect any approaching predators. For this bird species, it is in fact the females who court the males, and also compete with one another to grab the attention of the males. Mating takes place every day or on alternate days, culminating with the females laying 5 to 15 eggs every second or third day. Once the eggs are laid, the male starts brooding and hardly leaves the nest until the eggs are hatched completely. During this time, the males shed a lot of body weight and depend on stored calories for their survival. The female, however, leaves the brooding male in search of other mates. "Brood parasitism" is often observed in case of emus, wherein males are known to often incubate eggs that have not been fathered by them.