How did flightless birds evolve?

Question

How did flightless birds evolve and why do they still have bird-like anatomies?

Answer 1

It will have been beneficial to the species to lose the ability to fly. perhaps all there resources were located on ground level so flying became obsolete. Maybe it was more beneficial to develop larger bodies, perhaps for insulation or other survival strategies, making it initially difficult for the species to fly then eventually impossible, as they would be adapting to life on ground. The bird like anatomy maybe due to the fact that they simply have not long evolved to life on ground, or maybe there is no need for change.

Answer 2

They stopped flying- that's how. Over time the muscles that helped them fly devolved (from not being used) and they more than likely "genetically forgot" how. They maintain their anatomies partially because there hasn't been enough time for them to evolve out.

Specifically speaking, there are types of birds who live on very windy islands- if they were to fly away they'd be carried off, so they no longer take to the air. Perhaps they COULD still fly, but don't.

Answer 3

Animals have the instinct to survive. Survival requires use of the biome. Over time, an animal will become used to its environment, and adapts.

Answer 4

They were once flying birds as you know. But because of their environment, they lost their wings. For example, the penguin probably flew to Antarctica millions of years ago, and then figured that swimming is a better use than flying. So its wings changed to flippers and we have a penguin.

In the case of the ostrich/emu, it probably flew to australia. Figured the land had lots of good food, but predators were often chasing them. So they figured running would be a better use than flying. So there we go, now we have an ostrich.

You are right that even though the wings changed, the rest of the body didn't. And that's because these birds still consume and live in the same things they did before.. So to eat worms and nuts, they still need that beak. To reach high places, they still need that neck. To keep warm, they still need those feathers. To grip the ground and food, they still need those claws/talons. So the rest of the body stayed the same, only the wings changed.

Hope that helps =)

Answer 5

All species adopt to fit their enviroment. Perhaps these birds began discovering new ways to find food and hide from predators and spent most of their time on the ground. Over time, they lost the large wings they previously needed for flight, because they had now evolved to live their lives on solid earth.

Answer 6

Just a note to some of the other answerers; there is no such thing as "un-evolve" or "devolve".  Gaining traits and losing them is all plain old fashioned evolution.  Evolution means change.  Losing an ability is as much a change as gaining one.

Some birds became flightless because they grew large and heavy.  Some lost it because they lived in predator free environments and being good flyers was no longer an enforced adaptation.  Others exploited new niches that resulted in them evolving non flying lifestyles (like penquins).  

All living things live as energy conservative lifestyle as they can get away with.  Being able to survive without strain is ideal.  Anatomical features that become unnecessary tend to atrophy over many generations because there are no environmental pressures to keep them.  Lifestyle shapes the species and environment shapes the lifestyle.

Answer 7

For detailed information try Wikipedia, "tree of life web project".

Their anatomies, like yours and mine, bear evidence to their evolutionary history.

The larger you are, the more difficult flight is, since if you simply scale up, your weight increases as the cube of your length, but your wing area only increases as the square. So I assume that at some stage in their evolution, large birds will have diverged into those that limited their size, and those that continue to grow although their wings became increasingly useless. It may be relevant that flightless birds are commonly met with on islands, although I wonder how southern Africa fits in to this scheme.  I hope someone can give a more detailed answer.

BTW, I wonder what a creationist makes of these birds.

Answer 8

Usually birds fly to islands where no predators have come so they un-evolve there flight because they don't need to run away from predators.