Why in the world do Pigeons bob their heads when they walk?

Question

This has been bugging me all my life!

Swining one's arms is an option, we don't all swing our arms while walking, at least I don't. And pigeons don't swing their wings while walking, so weak analogy.

Answer 1

When we walk we can move our backs but birds can't because their vertebrae are fused (this makes it easier for them to fly). This means that other parts of their bodies have to move to make up for this and they appear to walk strangely.

Answer 2

Why do you swing your arms when you walk? (You don't have to . . .)