Waterfowl (ducks, geese, and swans) get their name from their tendency to stay in or near water. Their feathers are densely packed and waterproof, streamlining and insulating them for aquatic life. Nearly all waterfowl feed in the water, on aquatic grasses, seeds, roots, insects, mollusks, crustaceans, and/or small fish. Their webbed front toes help them paddle around looking for food. Typically, waterfowl have long necks and flattened bills with spiny tongues to grasp slippery food. Different species of waterfowl have different feeding techniques related to their diets. Mollusk-eaters use strong bills to yank mollusks off rocks, while fish-eaters have long, pointy bills for catching fish. In dabbling ducks, water is sucked in at the front of the bill, then pushed out the sides by a fleshy tongue. Hard, filter plates (lamellae) along the sides of the bill trap food like a sieve. Waterfowl often feed in flocks, making chattering sounds.

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.