Birds are often associated with flight, but not all of them take to the skies. Around 60 species — fewer than 1% of all bird species — are flightless, including ostriches, penguins and kiwis. These birds evolved from flying ancestors but lost their ability to fly, instead adapting to life on land or in the water.
But why did they give up flight? Why don’t all birds fly?
The ability to fly is especially useful for escaping predators and traveling long distances in search of food and favorable living conditions. However, flight requires a lot of energy; birds burn about 75% more energy per day than similarly sized mammals do.








