Owls will usually eat their prey whole unless there prey is too large to be swallowed whole they will use their hooked beaks to tear apart. The nutrients are absorbed in the stomach, and the undigested prey parts that are hard and of little nutritional value such as bones, bills, teeth, skuls, feathers or fur are compressed into pellets and regurgitated through the mouth in compact masses rather than excreted as feces. Owls regurgitate about two pellets each day, one at their daytime roost and one at their nighttime feeding site. A pellet is regurgitated about 6.5 hours after the meal. By counting the pellets under a roost site, you can determine how long the owls have been using the roost.
Where Owls Nest