Why does a robin jump and jump when walking?

It says it can't stop jumping. If it stops jumping, it can't go anywhere.

From Milne's children's poem "Jump", the original poem: A robin walked, jumped, jumped, jumped, jumped. Anyway, I'm going to tell it: don't jump when you walk. It says it can't stop jumping. If it stops jumping, it can't go anywhere. Lovely robin, so it always jumps and jumps when walking. Jump, jump, jump, jump.