Mark Grossman: The Rhea – the Ostrich’s and Emu’s American Cousin

20 February 2014

Africa has its ostrich, and Australia has its emu. However, many are unaware that the Americas have their version of these famous birds: the less-famous rhea.  This large, grey-brown bird is, on first sight, unmistakably the close relative of both the ostrich and emu.


However, the rhea grows to a height of just a bit under 6 feet, shorter than its, sometimes, 9 foot-tall cousin, the ostrich.  The rhea is, also, a comparative feather-weight at just 88 pounds when compared to its, sometimes, 240 pound African cousin.  But the rhea is fast enough to give the ostrich a good “run for its money.”  With a top speed of 40 mph, the rhea might not win a race against the fastest ostriches.  But that’s no disgrace because the ostrich, with its highest speeds clocked at about 43 mph, is the fastest land animal on earth.


Perhaps, speed compensates for flight.  Like the other members of its intercontinental family, the rhea is a completely flightless bird.  It’s preference for the ground earned it the name “rhea” given by German zoologist Paul Möhring, in 1752.  Named after a Greek Titan, Rhea, the name literally means “ground.”

Certainly, Möhring’s name is less creepy that the rhea’s native name, ñandú guazu, meaning spider!  The rhea earned this arachnid nickname through its habit of half extending its wings when it runs.  Although it’s actually using its wings for a bit of aerodynamic assistance, the half extended wings move up and down, as it runs, giving distant observers the impression of a giant spider.

Similar to the ostrich in appearance the rhea not only differs in its smaller size but, also, in its distinctly grey-brown plumage.  Unlike most birds, the rhea has 3 rather than 4 toes.  However, it doesn’t stand out as an oddity among its cousins.  The ostrich is the only bird on earth with only 2 toes.

And there’s another twist.  There are two varieties of rhea, the “Greater” and the “Lesser.”  Both live in about the same locations in South America.  A would-be birdwatcher might be frustrated because the two types aren’t so very different.   In other words, it’s hard for an observer, even at close range, to be able to tell the “greater” from the “lesser.”

Rheas are only found in South America — typically in the countries of Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay.  These birds tend to live in flocks of 20 to 25 and make an odd sight when the flock is frightened and running from danger. The individual birds and the flock run with a zigzagging course.  They use their wings as sort of “air rudders” extending one, then, the other to produce the zigzag motion.  As a matter of fact, for a flightless bird, the rhea uses its wings quite a bit.  But, as a running bird, it uses its wings more like a boat’s sails than an aircraft’s wings.


During mating season, the flocks dissolve as males and females pair off and mate. Though normally silent, during mating season, the male rhea makes an extremely loud booming noise.  An individual male will mate with several females.  After mating, the rhea’s home life mirrors that of the Australian emu.   Each female lays her eggs in a single nest — one every other day for a week to ten days, .  Then, the female abandons them to the male, who maintains the nest, sits on the eggs and otherwise cares for the eggs and hatchlings.



These birds have few predators other than human hunters.  In South America, rheas provide feathers for feather dusters, skins for leather goods and, even, eggs and edible meat.  Unlike Australia’s emu, the rhea is not raised as a ranch animal.

[video] Wild Kingdom