Grey rhea, Common rhea, American rhea; Ema (Portuguese); ñandú (Guaraní and Spanish)
The greater rhea (Rhea americana ) is a species of flightless bird native to eastern South America. The Greater rhea is the largest bird in South America and the largest native, extant bird anywhere in the Americas. It is also notable for its reproductive habits, and for the fact that a population has established itself in Northern Germany in recent years.
Greater rheas usually stand about 1.5 m (4 ft 11 in) tall to the top of the head. The males are generally bigger than the females. These birds have three toes, and the hind toe is absent. Their wings are rather long and rheas use them during running to maintain balance during tight turns, and also during courtship displays. Greater rheas have a fluffy, tattered-looking plumage, that is gray or brown, with high individual variation, The head, neck, rump, and thighs are feathered. In general, males are darker than females. Even in the wild - particularly in Argentina - leucistic individuals (with white body plumage and blue eyes), as well as albinos, occur. Hatchling Greater rheas are grey in color and have dark lengthwise stripes.
Greater rheas live are found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay. These birds live in grasslands as well as savanna, wooded pampas, and chaparral, though they prefer areas with at least some tall vegetation. During the breeding season (spring and summer), Greater rheas often stay near water.
Greater rheas are diurnal birds meaning they are active during the daylight hours. During the non-breeding season, they form flocks of between 10 and 100 birds. When in flocks, they tend to be less vigilant, but the males can get aggressive toward other males. When chased they will flee in a zigzag pattern, alternately raising one wing and then the other. They are very fast runners and are able to reach speeds up to 64 km/h (40 mph). The flocks break up in the winter in time for the breeding season. Greater rheas are silent birds except during mating season when they make low booming noises, and as chicks, when they give a mournful whistle.
Greater rheas are omnivorous birds. Their diet mainly consists of broad-leaved foliage, particularly seed, and fruit when in season, but also insects, scorpions, fish, small rodents, reptiles, and small birds. Sometimes, these birds gather at carrion to feed on flies; they are also known to eat dead or dying fish in the dry season, but as vertebrate prey in general not in large quantities. Rheas are also coprophagous and occasionally consume fresh fecal matter of other rheas.
Greater rheas have a polygynandrous (promiscuous) mating system in which both, the males and the females have multiple partners. After the large flocks break up in the winter, they form into three loose groups: single males, flocks of 2-15 females, and a large flock of yearlings. As winter approaches, males become more aggressive toward each other. Then they start courting females by calling and raising the front of their body up while keeping their neck straight and ruffling their plumage. They will raise their wings and may run some distance like this, sometime flapping their wings methodically. Once the male has attracted a first mate he will mate with her and then lead her to his nest. The female will lay her eggs in the same nest and the male will incubate alone; the female then will leave to mate with another male. Some males may utilize subordinate males to help incubate and protect the eggs. If this happens, the dominant male will find a second harem and start the process over again. The nests are thus collectively used by several females and can contain as many as 80 eggs laid by a dozen females; each individual female's clutch numbers 5-10 eggs. The nest is a simple shallow and wide scrape in a hidden location. The incubation period is 29-43 days. All the eggs hatch within 36 hours of each other. The chicks are half-grown about 3 months after hatching and become fully grown and independent at 6 months of age. During this time the male protects them. Young Greater rhea become reproductively mature by their 14th month of age.
Greater rheas are threatened by the increased hunting and the conversion of central South American grasslands to farmland and ranchland. The populations of Argentina and Uruguay are most seriously affected by the decline. Farmers sometimes consider these birds pests, because they eat broad-leaved crop and thus tend to hunt and kill Greater rheas. The burning of crops in South America has also contributed to their decline.
The IUCN Red List and other sources don’t provide the number of the Great rhea total population size. Currently, this species is classified as Near Threatened (NT) on the IUCN Red List, and its numbers today are decreasing.
