Extra favored Enemy( Masters of the Wild: A Guidebook to Barbarians, Druids, and Rangers, p. 22)
You select an additional favored enemy.
Base attack bonus +5, at least one favored enemy,
You add an extra favored enemy to your list (see Table 3-14 in the Player's Handbook) beyond your normal allotment. Initially, you gain the standard +1 bonus on damage and the usual skill checks against this new favored enemy. When you advance beyond the level at which you gained Extra Favored Enemy, this bonus increases in the same way other favored enemy bonuses do. For example, suppose you select goblinoids as your first favored enemy when you are a 1st-level ranger and magical beasts as your second when you reach 5th level. Then you take Extra Favored Enemy as your feat at 6th level and select aberrations. At this point, you have a +2 bonus against goblinoids and a +1 bonus against both magical beasts and aberrations. When you reach 10th level, your bonuses rise to +3 against goblinoids and +2 against magical beasts and aberrations.