American Ostriches are large, flightless birds native to North and South America. They are members of the Rheidae family, which is also known as Rheas. Rheas are large, flightless birds that are closely related to ostriches, emus, and cassowaries. They are found in open grasslands and savannas of South America. American Ostriches are the largest living bird species in the world, with males reaching up to 9 feet tall and weighing up to 300 pounds. They have long legs and a long neck, and their feathers are black and white.