Greater Rhea

Quick Facts

  • Scientific Name: Rhea americana
  • Spanish Name: Ñandú común
  • Family: Rheidae
  • Known Nicknames: Common Rhea, American Rhea, Ñandú
  • Average Length: 127–140 cm / 50–55 in
  • Average Weight: 20–27 kg / 44–60 lb
  • Wingspan: 150–250 cm / 59–98 in (used for balance and display, not true flight)
  • Key Feature: Large, flightless bird with long legs, a long neck, and soft, grey-brown plumage
  • Primary Diet: Omnivore
  • Range: Eastern South America (Brazil, Argentina, Paraguay, Uruguay, Bolivia)
  • Habitat: Grasslands, savannas, pampas, and open woodlands
  • Social Structure: Gregarious (forms flocks of 10–100 individuals outside breeding season)
  • Nesting/Breeding: Ground nest (a shallow scrape, often shared by multiple females)
  • Conservation Status: Near Threatened (NT)
  • Population Trend: Decreasing

The Greater Rhea (*Rhea americana*), South America’s largest bird, is a flightless, ostrich-like giant that roams the grasslands of Brazil, Argentina, and Uruguay. Standing up to 5 feet tall and weighing over 50 pounds, it boasts a shaggy, gray-brown plumage, long powerful legs adapted for sprinting up to 35 mph, and a distinctive, soft three-toed foot (unlike the ostrich’s two). A unique special feature is its polygynous breeding system, where males build nests, incubate clutches of up to 50 eggs from multiple females, and fiercely guard the striped chicks alone. With its booming, resonant call and ability to thrive in open pampas, the Greater Rhea is an iconic, keystone herbivore that shapes its ecosystem by dispersing seeds and controlling vegetation.

Fun Facts

The Greater Rhea has a bizarre courtship where a single male builds a large nest and then mates with multiple females, who all lay their eggs in it—up to 60 eggs from different mothers in one clutch. The male then incubates them for six weeks, rarely leaving to eat, and after hatching, he fiercely defends the chicks from predators, even charging at capybaras or humans. They are also surprisingly fast runners, reaching speeds of 40 mph (64 km/h) to escape threats, and they use their wings like sails to steer and brake during high-speed zigzag chases. Another quirky trait: they swallow large pebbles and sharp stones as gastroliths to grind up tough plant material in their gizzard, and they occasionally snack on poisonous snakes or insects without harm.

Habitats & Distribution

The greater rhea primarily inhabits open, grassy environments such as the pampas, savannas, and scrublands of central and eastern South America. It thrives in lowland areas with tall grasses and scattered bushes, often near water sources like rivers or marshes, and avoids dense forests and high-altitude regions. Its geographical range extends from northeastern Brazil and Bolivia south through Paraguay, Uruguay, and into central Argentina, with isolated populations also present in southern Brazil and northern Patagonia. The species has been introduced to parts of Europe, including Germany and the United Kingdom, but these are not part of its native distribution.

Behaviours & Reproduction

The greater rhea exhibits a polygynous social structure where dominant males establish territories and gather harems of three to six females. During the breeding season, males perform elaborate courtship displays, including wing-flapping, head-bobbing, and loud booming calls to attract mates. After mating, the male builds a large communal nest on the ground, into which all females in his harem lay their eggs—often 20 to 50 eggs total. The male alone incubates the clutch for about 35 to 40 days, fiercely defending the nest from predators. Once the chicks hatch, he remains the sole caretaker, leading and protecting them for up to six months, while the females depart to mate with other males. This strategy, where males invest heavily in paternal care while females maximize reproductive output across multiple partners, is a unique form of sequential polyandry.

Diet

The Greater Rhea is an omnivorous, opportunistic forager that primarily consumes a wide variety of plant matter, including broad-leaved foliage, seeds, fruits, and roots, often from crops like soybeans and sunflowers where it can become a pest. It also actively hunts for animal protein, eating large insects such as grasshoppers and beetles, as well as small vertebrates like lizards, snakes, and rodents. A fascinating dietary trait is its habit of swallowing small stones and pebbles, known as gastroliths, which collect in its muscular gizzard to mechanically grind tough plant fibers, a critical adaptation since it lacks teeth. Additionally, it is known to consume certain toxic plants that are avoided by other herbivores, suggesting a specialized digestive tolerance, and it will occasionally scavenge on carrion when the opportunity arises.

Colors

The Greater Rhea has predominantly gray-brown plumage, with a paler, whitish underside and a dark patch on the neck base. Adults show a subtle mottled pattern from darker feather edges, providing camouflage in grasslands. Males are slightly darker than females, and young birds have distinct dark stripes that fade as they mature.