Source: Complete Scoundrel
You have applied the hit-and-run tactics learned from scouting to your strong hunting abilities.
Prerequisite: Favored enemy, skirmish +1d6/+1 AC.
Benefit: Your ranger and scout levels stack for the purpose of determining the extra damage and bonus to Armor Class granted when skirmishing. For example, a 4th-level scout/1st-level ranger would deal an extra 2d6 points of damage and gain a +1 competence bonus to AC when skirmishing, as if she were a 5th-level scout.
Your ranger and scout levels also stack for the purpose of determining when you select additional favored enemies, as well as the total bonus granted against your favored enemies. For example, a 4th-level scout/1st-level ranger would have two favored enemies and could allocate an extra +2 bonus against one of those favored enemies, as if she were a 5th-level ranger.
In addition, your skirmish extra damage applies against any creature you have selected as a favored enemy, even if it is normally immune to extra damage from critical hits or skirmish attacks.
Special: A scout can select Swift Hunter as one of her scout bonus feats.