Birds
Greater Rhea
Rhea americana · also called greater rhea, common rhea, ñandú
The greater rhea is the ostrich of the Americas — a tall, grey, flightless bird striding across the pampas, big wings held out like sails when it runs. It is the biggest bird on two continents, and the whole burden of parenthood falls on the male, who guards his mixed brood of chicks with a readiness to charge anything that approaches.
Overview
Greater rheas live in the grasslands and open savanna of eastern South America — the pampas, cerrado, and chaco. They are social outside the breeding season, often mixing with deer, guanaco, and cattle, and feed as omnivores on plants, seeds, insects, and small animals, swallowing grit to grind it all down. They are flightless but fast, sprinting at around 60 km/h and using their oversized wings for balance and steering.
The male’s job
Rhea breeding is male-only care taken to an extreme. A dominant male mates with several females, who all lay in his single ground nest — a clutch that can hold 10 to 60 eggs from different mothers. He incubates for about 40 days and then raises the striped chicks alone for roughly six months, while the females go off to lay for other males. He is fiercely aggressive on the nest, charging people, horses, and vehicles.
Rheas in Germany
A handful of greater rheas escaped a farm in northern Germany around 1999 and founded a wild breeding population that has grown to hundreds of birds near the Baltic coast — the only self-sustaining wild rheas outside South America, now managed because they raid crops.
Status
The greater rhea is Near Threatened and declining, as the pampas and cerrado are ploughed for soy and grain and grazed by cattle, and as the birds are hunted and their eggs collected.
Greater Rhea: common questions
How is a rhea different from an ostrich or an emu?
All three are ratites — large flightless running birds — but they evolved on different continents and are only distantly related. The rhea is South American, the smallest of the three at up to about 1.7 metres and 30 kilograms, with three toes (the ostrich has two), feathered thighs, no tail plumes, and grey-brown plumage. The ostrich is African and the largest bird alive; the emu is Australian. The rhea also has proportionally larger wings than the others, which it uses for balance and steering while running rather than for any kind of flight.
Do male rheas really raise the chicks by themselves?
Yes, and to an unusual degree. A dominant male courts and mates with a harem of several females, who each lay their eggs in the one nest he has scraped in the ground. He then does everything — incubating the large clutch (which can hold 10 to 60 eggs from different mothers) for about 40 days, and then leading, brooding, and fiercely defending the striped chicks for roughly six months. The females move on to lay in the nests of other males. Sometimes a male recruits a younger "helper" male to take over one nest while he starts a second.
Are rheas dangerous?
Not usually, but a male on a nest or with chicks is a genuine hazard. He will lower his head, fluff up, and charge at speed, delivering kicks and pecks, and he will keep coming — accounts from the Argentine pampas describe brooding rheas driving off men on horseback. Outside the breeding season rheas are wary and run from people. They are far more threatened by humans than the reverse — they are hunted for meat, feathers, and skin, and their eggs are collected.
Why are there wild rheas in Germany?
In 1998 or 1999, a small number of greater rheas escaped from a farm near Lübeck in northern Germany, crossed a river, and settled in open countryside on the border with Mecklenburg. With no natural predators and suitable grassland and crops, the population grew steadily to several hundred birds. It is now the only self-sustaining wild rhea population outside South America, and local authorities manage it — including some egg control — because the birds damage rapeseed and grain fields.