There are several species of birds that cannot fly because they stopped using their wings for flying thousands of years ago. Perhaps neither the environment round them nor their living conditions wanted them to fly. Generally birds fly to protect themselves from enemies and in search of food. These flightless birds either lived in places where there were no enemies to prey on them or they were so big that they could rely on their legs to run away from trouble. As a result their wings fell into disuse and gradually they became flightless.
Kiwi
Do you known which are the birds which cannot fly?
First of all we have the penguins. They turned their wings into paddles or flippers. As a result they cannot fly but they are excellent swimmers. Theses birds mainly live in the southern hemispheres mostly at the edge of Antarctica .
The kiwis in New Zealand took to living by night, finding food by smell and almost ceased flying. Gradually the bird become flightless. It almost stopped using its eyes also and become weak eyed as well. These birds now have small wings which are hidden by hair like feathers covering their bodies.
The most ferocious flightless bird is the cassowary that lives in Indonesian jungles and is also found in Northern Australia and New Guinea . It is not scared of either man or beast and is quick to attack with the talons on its long legs.
The biggest flightless bird of the world is the African Ostrich mostly found in Savannah . Growing to a height of 2.5 eaters it can run at a speed of 60 kilometers per hour covering a distance of 4.5 metres in one stride.
Rhea is another flightless bird that lives in the grasslands of South America . The Australian emus is also a flightless bird next to the ostrich in size.
One interesting thing that has been observed by scientists is that most flightless birds live in areas where there are few natural enemies.