Bird (Class Aves)

This wing joint shows a 3rd Order lever: the coracoid and humerus bones form the fulcrum; the pectoralis muscle is contracting and adducting the humerus; the wing is moving downward.

This shows the wing after the pectoralis muscle has contracted to adduct the wing.

This lever has a high VR of around 15/1 and is obviously adapted for high-speed movements. However, this lever must also have a large MA in order to support a bird's body in the air. Because of this, the pectoralis and supracoracoideus muscles must produce a lot of force for a high-power wing movement.