Minecraft wiki entry for Skeleton, associated text: If a skeleton has a bow and a sword is given, it drops the bow, with the same chance as if killed with Looting I and starts using the sword. If a skeleton has a sword or bow in its hand, and one of a better type or with better enchantments is given, the skeleton drops the existing weapon, with the same chance as if killed with Looting I in favor of the better one. Any skeleton that spawns with equipment (picked-up items do not count) gives 1–3 extra experience points per item.