Greater Rhea(Rhea americana)
They are also known as the grey, common, or American rhea. The adults have an average weight of 20–27 kg and often measure 127-140 cm long from beak to tail; they usually stand about 1.5 m tall, with a typical range of 1.4-1.7 m, to the top of the head. The males are generally bigger than the females. The head and bill are fairly small, the latter measuring 8–10.4 cm in length. The legs are long, with the tarsus measuring between 33.5-37 cm, and strong and have 22 horizontal plates on the front of the tarsus.
They have three toes, and the hind toe is absent. The wings of the American rhea are rather long; the birds 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 grey 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 with dark lengthwise stripes.
There are five subspecies of the greater rhea; their ranges meet around the Tropic of Capricorn:
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R. a. americana – campos of northern and eastern Brazil
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R. a. intermedia – Uruguay and extreme southeastern Brazil (Rio Grande do Sul state)
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R. a. nobilis – eastern Paraguay, east of Rio Paraguay
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R. a. araneipes – chaco of Paraguay and Bolivia and the Mato Grosso state of Brazil
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R. a. albescens – plains of Argentina south to the Rio Negro province
Habitat
The greater rhea is native to Argentina, Bolivia, Brazil, Paraguay, and Uruguay. There are also feral populations of the greater rhea in Germany. This species inhabits grassland dominated by satintail and bahiagrass species, as well as savanna, scrub forest, chaparral, and even desert and palustrine lands, though it prefers areas with at least some tall vegetation. It is absent from the humid tropical forests of the Mata Atlântica and planalto uplands along the coast of Brazil and extends south to 40° latitude. They prefer lower elevations and seldom go above 1,200 metres. During the breeding season (spring and summer), it stays near water.
A small non-indigenous population of the greater rhea established itself in Germany. One male and five females escaped from a farm in Groß Grönau, Schleswig-Holstein, in August 2000. These birds survived the winter and succeeded in breeding in a habitat sufficiently similar to their native South American range. They eventually crossed the Wakenitz river and settled in Nordwestmecklenburg in the area around and particularly to the north of Thandorf village.
Diet
The rhea's 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. Favourite food plants include native and introduced species from all sorts of dicot families. Magnoliidae fruit or avocados can be seasonally important. They do not usually eat cereal grains, or monocots in general. However, the leaves of particular grass species like Brachiaria brizantha can be eaten in large quantities, and Liliaceae have also been recorded as foodplants. Even tough and spiny vegetable matter like tubers or thistles is eaten with relish. Like many birds which feed on tough plant matter, the greater rhea swallows pebbles which help grind down the food for easy digestion. It is much attracted to sparkling objects and sometimes accidentally swallows metallic or glossy objects. Rheas are also coprophagous and occasionally consume fresh fecal matter of other rheas.
Breeding
After the large flocks break up in the winter, they form into three loose groups:
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single males,
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flocks of between two and fifteen females, and
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a large flock of yearlings.
As winter approaches, males become more aggressive towards 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. After doing this and attracting females, they will continue calling at a specific female, and will start to either walk alongside her or in front of her while spreading his wings and lowering his head. As the display continues, he will get more intense and animated and start waving his neck around and in figure eights. Once he has attracted a first mate he will copulate with her and then lead her to his nest. When it is time for the eggs to be laid, the male will typically be on the nest already and will act aggressive when approached by the female, covering his nest with his wings. He will gradually relax and allow her to crouch and lay the egg at the edge of the nest. The male will roll the egg into his nest. Males are simultaneously polygynous, females are serially polyandrous. In practice, this means that the females move around during breeding season, mating with a male and depositing their eggs with the male before leaving him and mating with another male. Males on the other hand are sedentary, attending the nests and taking care of incubation and the hatchlings all on their own. Recent evidence has shown that some males will 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 some 5–10 eggs.
Rhea eggs measure about 130 mm × 90 mm and weigh 600 g on average; they are less than half the size of an ostrich egg. Their shell is greenish-yellow when fresh but soon fades to dull cream when exposed to light. The nest is a simple shallow and wide scrape in a hidden location; males will drag sticks, grass, and leaves in the area surrounding the nest so it resembles a firebreak as wide as their neck can reach. The incubation period is 29–43 days. All the eggs hatch within 36 hours of each other even though the eggs in one nest were laid perhaps as much as two weeks apart. As it seems, when the first young are ready to hatch they start a call resembling a pop-bottle rocket or even fireworks, even while still inside the egg, thus the hatching time is coordinated. Greater rheas are half-grown about three months after hatching, and sexually mature by their 14th month.
Population
According to the IUCN Red List, they are classed as Near Threatened(NT). The global population size has not been quantified, but this species is described as uncommon to fairly common. A moderately rapid and on-going population decline is suspected, owing to hunting for the species's skin and meat as well as the destruction and fragmentation of its habitat.
Threats
Its status is obfuscated by the presence of feral birds, but it has declined markedly partly owing to hunting for meat and the colossal export of skins. Over 50,000 skins were traded in 1980, most apparently originating in Paraguay, with Japan and USA leading consumers. In recent years, the large-scale conversion of central South American grasslands for agriculture and cattle-ranching has considerably reduced and fragmented its available habitat, particularly in the pampas and cerrado strongholds.
Conservation
Conservation Actions Underway
CITES Appendix II
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Conservation Actions Proposed
Monitor levels of illegal domestic and international trade. Effectively enforce restrictions on hunting and trade. Include pastures and grasslands in agricultural ecosystems. Preserve remaining natural habitat.