Owl pellet and contents of said pellet

Owl pellet and contents of said pellet

Observation - Owl pellet and contents of said pellet - UK and Ireland. Description: Dark grey almost black pellet about 2 inches in length found beneath an Oak tree on edge of wood. The skeletal contents of said pellet but what is it?

Dark grey almost black pellet about 2 inches in length found beneath an Oak tree on edge of wood.
The skeletal contents of said pellet but what is it?