Nice! You can tell a lot about the kind of raptor and what it eats by the size and contents of the pellet. There are people who specialize in analyzing pellets and reconstructing the skeletons of the prey. Great Horned Owl pellets are pretty large, ~2.5--5 inches. I've found pheasant feet and woodrat tails in GHOW pellets.

Recently, I found some medium sized pellets in our wildlife shelter belt. They were likely from either a Cooper's Hawk or a Long-eared Owl, both similar sized birds that had been roosting in those trees.

Small owl pellets are also recognizable. Here are some from a Northern Saw-whet Owl averaging 5/8 to 7/8 inches. I just collected a bunch from the slightly larger Western Screech-owl that measure about 3/4 to 1 1/8 inches. They contain tiny bones of mice, shrews, lizards and grasshopper parts. I frequently see owls and falcons regurgitating pellets, usually one or two pellets per day. It's a major upchuck for them.