Greater Rhea

The Greater Rhea is South America's largest bird, a flightless ratite found across open grasslands, savanna, and scrubland of the continent's southern and central regions. Standing over a meter tall on long legs, it is built for fast running rather than flight, much like its distant relatives the ostrich and emu.

Rheas live in flocks for much of the year, and males take on sole responsibility for incubating eggs and raising chicks after gathering a shared clutch from multiple females, an unusual breeding system among large birds.

• Body plumage is soft and loose, with feathers lacking the interlocking barbules of flighted birds, giving a shaggy, hair-like texture
• Overall color is grayish-brown above, paler grayish-white on the underparts and flanks
• Males show a blackish patch on the foreneck and upper breast during the breeding season, more pronounced than in females
• Wings are reduced and non-functional for flight, used instead for balance while running and in display, with loose plumes rather than structured flight feathers
• Distinguished from the Lesser Rhea by larger size, unspotted plumage, and lack of the fine pale speckling seen in that species

Adults show grayish-brown plumage overall, with males developing a darker blackish patch on the neck and breast, especially pronounced in the breeding season. Females and nonbreeding males are more uniformly pale grayish-brown without the dark neck patch. Chicks are downy and striped in gray and buff for camouflage in grass, gradually molting into the adult's soft plumage over the first year.

The Greater Rhea inhabits open grassland, savanna, and scrub habitats across central and southern South America, including parts of Brazil, Argentina, Paraguay, Uruguay, and Bolivia. It is a resident, non-migratory species, though flocks may shift locally in response to food and water availability across open plains.

Rheas are omnivorous, feeding on grasses, seeds, and various small invertebrates encountered while foraging on open ground. Males build a ground nest and incubate a communal clutch of eggs contributed by multiple females, then care for the chicks alone. Rheas are largely silent apart from booming or roaring calls given by males during the breeding season, and they rely on speed and keen eyesight to evade predators across open terrain.