Owl pellets are not fecal matter (or poop), they are masses that owls regurgitate up from their gizzard. When owls feed on birds, rodents or other animals, they swallow bones, fur, and other tissues that they can’t digest. They regurgitate this back up as pellets that drop to the ground below their roosting areas. Careful dissection of these pellets and identification of the bones reveals what the owl’s meal consisted of.
Owl fecal pellets may contain biologically active pathogens, such as viruses, bacteria or fungi. When handling any materials of this type from wild animals, be sure to keep your hands away from your face and mouth while working and wash your hands thouroughly when finished. Children should be supervised carefully by an adult.
You can read more about owl pellets at the following website:
The Carolina Biological Supply website also provides some excellent guides to help with identification of small bones. Here are some pdfs from their website to help you get started:
Bird skeleton – birdskeleton
Bone chart – bonechart
Owl Pellet Bone Chart grid – Owl_Pellet_Bone_Chart_grid
Rat Skeleton – ratskeleton
Mole Skeleton – moleskeleton