 Lacking in hands or tools beyond their bills, most birds have to swallow their food whole. This means they'll often consume materials that they cannot digest, so they'll have to regurgitate it in the form of a pellet. Owls are perhaps the most famous for their pellets because they are easy to find. Lacking strong acids in their stomachs, owl's pellets can be large in their contents, such as fur and bones, will typically remain intact. There are a lot of other birds that also cast pellets. This includes hawks and other raptors, but they are capable of picking apart their prey, so pellets tend to be smaller. Even some gulls, shorebirds, and songbirds, like warblers and thrushes, will also produce pellets. If you find one, it can be very entertaining to dissect and see the caster's last meal. Here's a time lapse of one we recently found. It was mostly held together by dark feathers, but you can see here a bill being exposed, including the rest of the skull. Now a leg, and a different bird's foot, then the other leg, and a tibiotarsis, probably to go with one of those feet. This was the most amazing part. An entire limb, apparently from a grackle, which makes sense given all the dark feathers, plus some ribs and the clavicle, or wishbone, now on the top right. Given the contents of this pellet were from small birds, and it was found near the remains of a duck, I would suspect one of our local peregrine falcons was involved, although it is impressively large for that species. As a quick comparison, here's another type of pellet you might find, but only in the summer. It is from an American toad. You can see the pinchers from European earwigs on the left, shell casings from beetles in the middle, and an intact pellet on the right. Keep an eye out for pellets year-round, anytime you're out enjoying nature.