The Woodpecker

This woodpecker doesn't slip but descends at a measured step. The ring, which the woodpecker is hanging at, slides a little, then it fits in and the woodpecker swings and pecks.

The cause for these small hops is the static friction between the ring and the staff. The spring is needed to store elastic energy and to allow the next oscillation.

Have you ever seen high poles during the popular games in Bavaria? The competitors climb up them like anti-woodpecker, while the poles are frictionless to make this climbing more difficult.