This big bird (weighing up to 12 kg) is white with a black knob, lower bill and legs. Upper bill is orange. Black basal knob on the upper bill stretching to its forehead is the best distinctive feature of the Mute Swan. The Mute Swan holds its neck curved while swimming, bill bending downwards. It can be often seen to hold its wings up above the back like a shield. The Mute Swan is a very silent bird but it will hiss or snort when annoyed.