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.

Most birds fly. Wing feathers are spread out to increase surface area and generate lift like airplane wings. Soft contour feathers overlap rigid flight feathers to make a streamlined but firm surface. Stiff tail feathers are used to steer and break. Unlike an airplane, a bird flaps its wings to generate thrust for forward movement. A typical bird body is adapted for flight. Hand bones are fused together to support the flight feathers. A downward extension from the breastbone provides a place to anchor large chest muscles that power the wings. Bird bodies are surprisingly light, thanks to thin-walled, hollow bones. For strength, the hollow channels are filled with bony struts like the scaffolding of a building. Many birds also spend a lot of time standing and walking. Their pelvic girdle is strong, supporting the bird's weight on just two hind limbs.