At up to six feet tall and 60 pounds, the Greater Rhea is the largest bird in the Americas. A member of the group commonly known as ratites (large, flightless birds), their large size, long legs, and lack of ability to fly makes them unmistakable.
Although they don’t take flight, Greater Rheas have long wings; the birds use them to maintain balance on tight turns as they run at speeds up to 40 miles per hour, and also during courtship displays. A real athlete, this bird can even swim.
Although the Greater Rhea resembles an ostrich—in fact, Charles Darwin first described it as a “South American ostrich”—the two species are not closely related. Greater Rheas are social, living in mixed flocks of up to 30 or more for most of the year. They often forage with Pampas deer, guanacos (wild llamas), and domestic animals, a behavior that allows them to find food more readily and gives an element of protection from predators.
Natural predators of adult Greater Rheas are limited to the cougar and jaguar. However, human impacts take a major toll on the species: The population has declined substantially due to hunting for the bird’s meat, eggs, skin, and feathers. An even bigger threat may be habitat loss, as vast areas of grasslands are converted to cattle ranching and agriculture.
The recent expansion of the Barba Azul Nature Reserve in Bolivia is excellent news for this species. Other birds that will benefit are the resident Blue-throated Macaw, Cock-tailed Tyrant, Orinoco Goose, as well as the migratory Buff-breasted Sandpiper and Bobolink.
During the breeding season, male rheas become solitary and territorial, and females split into small groups of up to 12 individuals. Males fight to attract the females to their area. Each female lays up to 10 eggs per day in the nest—a simple scrape made by the male—which leaves him with a nest full of up to 80 eggs to incubate! The males rear the young without assistance from the female, taking care of them for up to four months.
“Greater Rheas are present throughout the tropical grasslands of Bolivia,” says Bennett Hennessey, Executive Director of Asociación Armonía, ABC’s Bolivian partner, “but their behavior varies in different places. In some areas, you can only see a bobbing head and a dust cloud left as they run away, but in other areas, like the Barba Azul Nature Reserve, they forage and walk around less than 20 feet away, with no apparent concern for human presence.”
Birders and other tourists interested in visiting this fascinating place can book a stay at Barba Azul through our Conservation Birding website. Our friends at Asociación Armonía would be thrilled to see you.