Greater Rhea (Rhea americana)

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Image of a Greater rhea
Birds Rhea

Introduction

The Greater Rhea, Rhea americana, is a large flightless bird of eastern and central South America. It is the largest living bird in South America and inhabits open landscapes, including grasslands, savannas, pampas and lightly wooded areas. Also known locally as the ñandú or ema, it is an important herbivore and opportunistic omnivore within these ecosystems.

Physical Description

Greater Rheas stand about 0.9–1.5 metres tall and generally weigh 15–30 kilograms. They have long, powerful legs, a long neck and a small head, with three toes on each foot. Their loose plumage is mainly greyish brown, with paler underparts. Unlike many large flightless birds, they have relatively long wings and no prominent tail feathers. The wings are used as rudders and stabilisers during fast running and sudden changes of direction, rather than for flight.

Males are usually larger than females and may develop a darker collar at the base of the neck during the breeding season. Juveniles are browner and more strongly marked than adults, helping them blend into grass and scrub. Their large eyes and long eyelashes provide protection from dust and vegetation in open, often dry habitats.

Range and Habitat

The species occurs across parts of Argentina, Bolivia, Brazil, Paraguay and Uruguay. Its range includes the Pampas, Cerrado, Chaco and other open or semi-open landscapes. Greater Rheas use tall grasslands, savannas, open woodland, scrub and some agricultural areas, although natural grasslands generally provide better habitat than intensively cultivated land.

They are usually associated with lowland and gently undulating country, but may occur at elevations of at least 1,200 metres in suitable habitat. Breeding birds often use areas close to rivers, lakes, marshes or other reliable water sources. Greater Rheas are not long-distance migrants, although local and seasonal movements can occur in response to food, water and land-use conditions.

Behaviour and Diet

Greater Rheas are mainly diurnal and spend much of the day walking while feeding. Outside the breeding season they commonly form groups, sometimes alongside deer, cattle or other large grazing animals. Their speed, long stride and ability to turn quickly help them evade predators. Adults are generally quiet, although males produce a deep booming call during courtship and breeding.

The diet is dominated by broad-leaved plants, grasses, clover, seeds, roots and fruit. Insects and other small animals, including lizards, frogs, snakes and small birds, may also be taken, particularly when available. This varied diet makes the species an opportunistic omnivore, although plant material forms the main part of its food in many habitats.

Breeding is polygynous. A male establishes a nest site and may mate with several females. The nest is a shallow depression on the ground, into which several females lay eggs. A single nest may contain many eggs, sometimes more than 40, contributed by multiple females. The male incubates the eggs for about six weeks and provides the main parental care after hatching. He leads, shelters and defends the striped chicks, and may charge animals or people that approach too closely.

Identification Tips

  • Look for a very large, flightless bird with a long neck, long bare legs and a rounded, feathered body.
  • Grey-brown plumage, pale underparts and three toes on each foot are useful field marks.
  • The long wings are conspicuous when the bird runs and are often spread during rapid turns.
  • Greater Rheas are smaller and less heavily built than Ostriches, and they have three toes rather than two.
  • They are generally browner and larger than Lesser or Darwin’s Rheas, Rhea pennata, which are associated with more southerly and often higher-elevation habitats.

Conservation Status

The Greater Rhea is listed as Near Threatened on the IUCN Red List. The principal threats are the conversion and fragmentation of natural grasslands, hunting, collection or destruction of eggs, and mortality associated with agricultural activities. Fences, roads and intensive cultivation can also reduce habitat quality or restrict movement.

Conservation measures include protecting and restoring native grasslands, maintaining connected habitat, managing fencing and reducing illegal hunting and egg collection. Extensive grazing systems may retain useful habitat when they are managed in ways that preserve vegetation structure and nesting areas. Because the species also uses some modified landscapes, cooperation with landholders is an important part of its conservation.

Frequently Asked Questions

Where does the Greater Rhea live?

The Greater Rhea lives in Argentina, Bolivia, Brazil, Paraguay and Uruguay. It is associated mainly with grasslands, savannas, pampas, open woodland and scrub.

Is the Greater Rhea able to fly?

No. The Greater Rhea is flightless. Its wings help it balance and steer while running, but they cannot generate sustained flight.

What does the Greater Rhea eat?

It mainly eats leaves, grasses, clover, seeds, roots and fruit. It also takes insects and small vertebrates such as lizards, frogs, snakes and small birds when opportunities arise.

Do male or female Greater Rheas incubate the eggs?

The male incubates the eggs and raises the chicks. Several females may lay eggs in the same nest, after which the male provides most of the incubation, protection and chick care.

How can a Greater Rhea be distinguished from an Ostrich?

Greater Rheas are smaller, have three toes on each foot and usually have grey-brown plumage with pale underparts. Ostriches are larger, have two toes and a different body shape and plumage pattern.

Why is the Greater Rhea Near Threatened?

Its main problems are habitat loss and fragmentation, hunting, egg losses and hazards associated with agriculture, roads and fencing. Protecting large areas of connected grassland is central to its conservation.

References

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