Flightless Bird

flightless bird, any of several birds that have, through evolution, lost the ability to fly as they adapted to new environments. Most living forms belong to the order Struthioniformes (a group that includes the ostrich, the rhea, the cassowary, the kiwi, and the emu); however, they are more commonly known as ratites. Also flightless, but unrelated to the ratites, are penguins (order Sphenisciformes). Several extinct forms, such as the dodo, are known from historical records and from fossils.