Flightless birds
Flightless birds are birds which cannot fly. They rely on their ability to run or swim, and have evolved from their flying ancestors. There are about 60 species living today, the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguin. Flightless birds have smaller wing bones and a greatly reduced or absent keel on their breastbone.  The keel anchors muscles needed for wing movement. Flightless birds also have more feathers than flying birds.