Greater rheas are a type of flightless large bird that live in South America. They look similar to emus on first glance, but are smaller and paler. In particular, they have much paler heads, necks and legs than emus (which themselves have black feathers on the head). They are social birds, most being found in mixed-sex flocks of up to 30 or more, with the exception of older males, which may be solitary. Their breeding habits are unusual as males raise the young. Males defend a territory in the mating season where they will display to females, attempting to mate so they will lay eggs in the nest he has prepared.