The Columbia Encyclopedia, Sixth Edition. Columbia Encyclopedia World Factbook American Heritage Coll. The rhea also differs from the unrelated ostrich in structure of the palate, pelvis, and foot. It is yellow and gray above, with a black head and dirty-white underside. The rhea is typically a creature of the pampas and savannas and may often be found feeding in mixed herds along with cattle or guanaco, occupying an ecological niche similar to that of the ostrich and the zebra of Africa.
Rheas feed on several kinds of plants, insects, and small vertebrates.
While the old males tend to stay solitary, the young male is aggressive and highly polygamous, gathering about itself from three to seven hens. The nest is built in a dry and protected area, preferably near water. The male excavates a shallow hole with his bill, lines it with dry vegetable matter, and assumes all the incubation duties. He may incubate as many as 50 eggs, produced by a number of females over a period of weeks. Incubation takes from 35 to 40 days.