How birds evolved the ability to fly

Okay, I'm not a paleontologist or anything, but I think I might have figured something out. I've heard a couple of theories on how birds may have evolved the ability to fly. One is that they started by gliding, either to avoid predators or to catch prey. The idea was that they would climb a tree or somthing, then swoop down to catch something. The best gliders survived the best and passed their gliding genes on to their offspring. Over the generations, the species got better and better at gliding until gliding turned into flying.

Another theory I read recently was that birds may used their wings to help them go uphill. Some scientist recently noticed that when baby birds walk uphill, they flap their wings to try to give them a little lift to help them go up faster. Since developing youngsters often go through stages that are similar to earlier forms of the species (ontogeny recapitulates phylogeny), this would seem to indicate that primitive birds might have gone through a stage where they used their wings to help them go uphill. Maybe there were climbing up a hill so that they could jump off the cliff on the other side and swoop down on some prey. :)

I think the real reason birds learned to fly was by chasing flying insects. Picture this, you've got some small two-legged dinosaur, similar to compsagnathus with strong back legs and small arms, running around trying to catch flying insects. Now this dinosaur, we'll call him Bob, is running around real fast, and this insect is flying up and down just out of reach. Bob tries to jump to catch the insect in his mouth. The better Bob is at jumping, and running fast, the better his chances for survival. Some of the adaptations that might best suit Bob's lifestyle would be to make him light weight. This adaptation would also suit his descendents as they learn to fly.

Another adaptation would be to raise his arms up just before jumping, then pull them down fast as he makes the jump. Through conservation of momentum, pulling his down will help lift his body up, allowing him to jump higher. If we assume that this dinosaur had feathers, perhaps adapted earlier for warmth, then any individual whose arm feathers stuck out a little would catch the wind with its downward arm thrusts, thus giving it even more lift.

As the generations passed, the arms would turn into more winglike appendages, and the thrust aspect of throwing the arms down would outweigh the momentum aspect, and it would become advantageous to throw the arms down multiple times to keep oneself aloft longer. This would of course turn into flying over the generations.

The main difference between birds and bats is that the thrust surface for birds is made of feathers, whereas in bats it is made from skin. Therefore, I think we can assume that if birds didn't have feathers before learning how to fly, they would have evolved wings that look more like those of bats. I know there's been a lot of stuff in the media lately about some dinosaurs having feathers, like that one found in China a year or so ago. I don't remember if that dinosaur had any kind of proto-wings, i.e. the feathers stuck out rather than lying flat agains the arms like they do against the rest of the body. Any way, that, plus the fact that the feathers on the rest of a birds body lie flat, makes me think that the feathers came first, then evolved into flight feathers to give the dinosaur additional thrust.

One possible reason for having evolved feathers is to keep the muscles warmer so that they can generate enough energy for sustained rapid movement. This would be an advantage if your prey was a fast moving flying insect, but it would also be an advantage against a lot of other prey.

If this theory is correct, it may provide an example of something else that I've thought a lot about lately. This is another subject unto itself, but I'll try to sumarize it briefly here. It has something to do with convergence, and how different species can independently evolve similar structures to solve a common problem. A prime example of this is how birds, bats and insects all evolved similarly functioning wings to accomplish flying. It is generally assumed today that each of these "flying phylums" developed these capabilities independently, but what if that's not the case. Certainly the genes for wing structure can't be passed from an insect to a dinosaur, but the idea for flying can. Insects learned how to fly first, I think that's pretty well established, and I think, therefore, that they deserve the credit for "inventing" flying. Birds learned how to fly next, and I think they've been given credit for inventing the ability to fly all on their own, but if my theory is correct, they really kind of get the idea from insects.

Anyway, like I said, I'm not a paleontologist, and I don't have time to really chase down this theory. There may already be stuff that's been found that disproves this theory and that I'm simply not aware of. Or, it's possible that this is already an established theory and that I simply haven't heard of it yet, or heard of it so long ago that I've forgotten it. However, "hope springs eternal", and I'm hoping that this is a new theory, so I'm documenting it here on blogger, along with a time stamp. I came up with this theory while driving home from work last Friday night (I think about a lot of stuff while driving home), Feb. 27, 2004, at around 6:00 PM, Pacific Standard Time.