The Family Rheidae consists of large, flightless birds known as rheas, native to South America. These birds are similar in appearance to ostriches and emus but are smaller and have three toes on each foot. Rheas are herbivorous, feeding mainly on grasses, seeds, and fruits, though they may occasionally eat insects. They are fast runners, using their speed to escape predators, and typically live in open grasslands or savannas. Rheas are social, often forming small flocks, and they exhibit unique reproductive behavior, with males building nests and incubating eggs from multiple females.