Hum... We are a bit optimized for flexibility, and a lot the way we are by accident. As many people already said in other threads, we are probably the least optimized walking animal of all, because our body is recent and walking efficiency was never as relevant as other characteristics (like flexibility).
The birds body, by their turn, appeared in a time closer to the first animals than to today, took over the lands of the world in large part because of their ability to run, and kept them for more time than any other kind of animal.
There are some freedom in robot bodies that animals don't have. So it's not immediately obvious that an animal inspired body is perfect. But birds have had hundreds of millions of years to perfect their shape, it's not clear that we can do any better either.
The birds body, by their turn, appeared in a time closer to the first animals than to today, took over the lands of the world in large part because of their ability to run, and kept them for more time than any other kind of animal.
There are some freedom in robot bodies that animals don't have. So it's not immediately obvious that an animal inspired body is perfect. But birds have had hundreds of millions of years to perfect their shape, it's not clear that we can do any better either.