Birds feet seem impervious to heat and cold because they consist primarily of strong tendons with few nerves and blood vessels. The largest diving duck in North American marshes and estuarine bays and lagoons is the Canvasback. The largest duck of the northern hemisphere is the Common Eider. Baby grebes are fed on fish, but their parents also feed them feathers from their own bodies. The feathers may prevent fish bones from injuring the baby grebes stomachs.
Most birds eat relatively large quantities of food in proportion to their body weight.
A female wood duck will generally return each year to the same tree cavity to lay her eggs and hatch her ducklings. A crowd of cows is called a herd . Migrating geese make loud, honking noises, called contact calls, to help them stay together. Dabbling ducks have broad wings that enable them to rise immediately from the water or ground into flight. Diving ducks have much smaller wings and need to run across the surface of the water while building up speed in order to become airborne, much like an airplane taxiing before takeoff.