You are skilled at defending yourself while dual-wielding.
Benefit: When wielding a double weapon or two weapons (not including natural weapons or unarmed strikes), you gain a +1 shield bonus to your AC.
When you are fighting defensively or using the total defense action, this shield bonus increases to +2.
Pathfinder RPG Core Rulebook. Copyright 2009, Paizo Publishing, LLC; Author: Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.