How birds learned how to fly

The question of how birds evolved the ability to fly has been an ongoing debate for centuries.  To try and answer this question we will first discuss reasons why birds fly. Then we will look at four different theories that have emerged to attempt to explain how birds took to the skies. Finally, we will briefly discuss what, if any, expert consensus there is about how birds evolved the ability to fly.

A roseate tern - US FWS - Public Domain

Powered flight takes up a lot of energy and many large species use air currents and updrafts to glide and soar so they do not have to flap their wings. This is a good way for them to save energy.  But if flying takes up so much energy why use it at all?  Read more