Owls are expert night hunters of birds, lizards, insects, mice, or even fish. Various adaptations make them skillful at catching prey in low light. The feathers across the front of their faces are flattened into a disk, surrounded by a fluffy ruff, which channels sound toward the ears. In many owls, uneven placement of the ears on their skull allows them to pinpoint the location of sounds with extreme accuracy. Owl eyes have extra light-sensing cells (rods) packing into tubular eyeballs that extend back into their heads. The eyeballs cannot move in their sockets, but owls instead swivel their necks more than 180 degrees to see what is behind them. Fringed, soft feathers on their wingtips act as mufflers, making for silent flight as owls sneak up on prey. Owls regurgitate parts of their meals, spitting out a pellet made of fur, feathers, bones, or other indigestible body parts.

All modern birds have bills and no teeth. The shape of a bird's bill says a lot about what it eats, for example whether it specializes in seeds (stout , cracking bill), fish (pointy, spearing bill), or plants (wide, serrated bill). Birds swallow their food without chewing, so it travels to the stomach whole or in large pieces. Bird digestive tracts have some special features for digesting chunky food. A pouch in their throat (the crop), is used to store food to be digested later, or regurgitated to feed the young. An extra, muscular stomach (the gizzard) grinds food up. Birds are endotherms, using heat they make internally to keep warm. While a few species allow their body temperature to drop at night (torpor), a nearly constant body temperature is maintained by most birds most of the time. Continuously making heat requires fuel to burn, in the form of food. So, birds spend a lot of time eating.