Somebody explain this cat behavior (as if cat behavior can be explained).

[RockCreek]

4. Most likely he's trying to keep it in sight.

But how old is he? How are his joints? His weight?
He could be taking the easier route.

I think I remember seeing some of my cats doing the above the ground thing, especially when they are making the birding "trilling" noise and are really into the hunt. I've just never really thought about it before.