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Rhea (bird)

life science Maturity 7-9 Next article →

The rhea is a large, flightless bird native to South America.

Nandu, Parque Luro, La Pampa, Argentina
Nandu, Parque Luro, La Pampa, Argentina

These birds are classified as ratites. A ratite is a type of bird that lacks a keel on its sternum, or breastbone. This physical difference means they cannot fly. Rheas belong to the order Rheiformes. They are distantly related to the African ostrich and the Australian emu. In terms of overall size and height, the rhea is the third-largest living ratite.

Greater rhea skeleton
Greater rhea skeleton

Most taxonomic authorities recognize two main species of rhea living today. The first is the greater rhea, also called the American rhea (Rhea americana). The second is the lesser rhea, or Darwin's rhea (Rhea pennata). Some organizations, like the IUCN, classify the puna rhea as its own species rather than a subspecies of the lesser rhea. These birds are physically distinct. Large male greater rheas can reach 2.1 meters in height. They can also weigh up to 35 kilograms. In contrast, the lesser rhea is much smaller, reaching a height of only 1.5 meters.

Greater rhea close up
Greater rhea close up

Rheas have several unique physical traits that help them survive in open environments. They possess long necks and long legs covered in grey-brown plumage. Unlike most other birds, rheas have only three toes on each foot. Their tarsus, or lower leg, features 18 to 22 horizontal plates on the front. Even though they are flightless, their wings are quite large. When a rhea runs, it spreads its wings to act like sails. If the bird senses danger, it flees in a zigzag course. It uses its wings like rudders to steer through the landscape.

Rhea dustbathing at Marwell zoo
Rhea dustbathing at Marwell zoo

The history of the rhea's name is linked to ancient mythology. In 1752, Paul Möhring used the name "rhea" for the bird. He named it after the Greek Titan Rhea. The name of the Titan is thought to come from the Greek word "éra," meaning "ground." This is a fitting name for a bird that lives its life on the earth. In 1760, the French zoologist Mathurin Jacques Brisson introduced the genus Rhea. He used the greater rhea as the type species for this group. In South America, the birds have many local names. For instance, the Guaraní name "ñandú" likely means "big spider." This refers to how they move their wings while running.

Rheas are mostly herbivorous, meaning they eat plants. They prefer broad-leafed plants, but they also consume fruits, seeds, and roots. They will occasionally eat insects, small reptiles, or rodents. During the breeding season, the birds follow a complex social system called polygynandry. In this system, a single male may court between two and twelve females. Simultaneously, females may mate with multiple dominant males. The male takes on the primary responsibility for the nest. He builds a simple scrape in the ground lined with leaves and grass. A male may incubate between ten and sixty eggs at once.

Carne de ñandú
Carne de ñandú

To protect their offspring, males use a clever decoy system. The male will place some eggs outside the main nest. He sacrifices these decoy eggs to predators to keep the real nest safe. While the male incubates, he may even use a subordinate male to help. Young chicks hatch within 36 hours of each other and begin to whistle right before they emerge. While the male cares for the chicks, he will charge at any perceived threat. This includes humans or even female rheas. Although chicks grow to adult size in six months, they do not breed until they are two years old.

Human interaction with rheas varies by region. In South America, they are used for meat, skins, and feathers. Gauchos have traditionally hunted them on horseback using bolas. These are throwing devices with three balls joined by rope to immobilize the bird. Interestingly, rheas have appeared in unexpected places like Europe. In Germany, a feral population emerged after birds escaped a farm in the late 1990s. By 2018, this population grew to about 600 birds. However, the population has since fluctuated due to hunting and harsh weather.

Greater rhea (Nandu), Lenschow
Greater rhea (Nandu), Lenschow

Conservation remains important, as the greater and puna rheas are currently listed as near-threatened by the IUCN.

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🖼️ Images & Media (6)
File:Rhea dustbathing at Marwell zoo.JPG
Rhea dustbathing at Marwell zoo.JPG
File:Greater rhea close up.jpg
Greater rhea close up.jpg
File:Nandu, Parque Luro, La Pampa, Argentina.jpg
Nandu, Parque Luro, La Pampa, Argentina.jpg
File:Greater rhea (Nandu), Lenschow.jpg
Greater rhea (Nandu), Lenschow.jpg
File:Greater rhea skeleton.jpg
Greater rhea skeleton.jpg
File:Carne de ñandú.JPG
Carne de ñandú.JPG
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