Legend of the Guardians: The Owls of Ga'hoole

Some enemies have armor equipped. This is signified by an ironish bird helmet looking thing that covers their health bar. Before you can do damage to them, you must break their armor. The ability to break armor is unlocked as you defeat enemies. Unfortunately, if you avoid battles it is possible to encounter these enemies before you've unlocked the ability. In this case, you will have exit the level and replay old levels defeating enemies to until you unlock that barge skill. Now, to break an enemies armor, you should lock on to them with and press  when your reticle turns red.