Some birds Have lost the ability of flight which are called flightless birds. They are group under order Ratitae. Whings are reduced, Legs are well developed. Keel is absent in the sternum. 
a) Kiwi ( Apteryx) :
It is the smallest flightless bird. It is a New Zealand emblem bird.

b) Penguin (Aptenodytes): Gregarious flightless birds and live in cold sea waters of the south pole specially in Antarctica.

c) African Ostrich ( Struthio) : Largest living bird, prominent eyes, can run at the speed of 80 kms per hour. Foot bearing two unequal toes provided with pads, with help the bird in fast running.

d) Cassowary (Casuarius) : World’s largest flightless bird; lives in Austarilia, New Guinea and adjacent islands.

e) Emu (Dromiceius): Next to ostrich, emu is the largest living bird. It is confined to Australia, invariably monogamous though seen in small parties after breeding.
Examples of Flightless Birds

f) Rhea: Smaller than Ostrich but its habits are quite to ostrich.
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