Why Are There Flightless Birds?

[UngulateNerd92]

Penguins can “fly” under water

The ability to fly seems to define birds. But there are more than 50 species of flightless birds throughout the world — from the Ostrich and Kiwi to flightless rails, ducks, and this Humboldt Penguin. Why did they evolve the inability to fly? Many dwelt on islands. Others evolved until they were huge -- like the extinct 12-foot-tall Moas of New Zealand. And the penguins? Unlike most flightless birds, they still have the strong flight muscles and keeled breastbones of flying birds. They are supremely graceful flyers. But they do it under water.

Why Are There Flightless Birds? | BirdNote

 

[Dassie rat]

Basically, flying uses up a lot of energy, produced from food. If a bird has enough food nearby throughout the year and can run fast enough to escape predators, it probably doesn't need to fly. If a bird lives on an island with a tendency of strong winds, if it flies, it could be transported by the wind to another island, far from home. Being unable to fly and having enough to eat helps the bird adapt to the environment it lives in.

 

[UngulateNerd92]

Basically, flying uses up a lot of energy, produced from food. If a bird has enough food nearby throughout the year and can run fast enough to escape predators, it probably doesn't need to fly. If a bird lives on an island with a tendency of strong winds, if it flies, it could be transported by the wind to another island, far from home. Being unable to fly and having enough to eat helps the bird adapt to the environment it lives in.

Great explanations, thank you.

 

[Greaterbilby]

A complementary explanation could also be this: since via flying, birds can spot and stay or thrown on remote islands, there is little possibility these islands have competitors. This way, they would evolve in a land mammal lifestyle, occupying niches that otherwise would by occupied by mammals.