There is also a prominent black knob at the base of its bill. Another distinctive characteristic is the graceful curved neck held in an S-shape with the bill pointed downward while the bird is swimming. The male mute swan, or cob, is usually larger in size with a more prominent knob on his forehead but is otherwise identical to the female, or pen. Young swans, called cygnets, are usually white, but gray-colored cygnets are not uncommon. Approximately 150 pairs of mute swans have been recorded nesting along the Connecticut coast and up to 20 miles inland along the major rivers, and in some inland lakes and ponds.
Most mute swans breed at age three and remain with the same mate for life.
Flooding is a common cause of nest failure. If a nest is lost, renesting may occur until late spring. An average of four to six eggs are laid in a three to four- inch depression in the nest center and incubated by the pen for 36 to 38 days. The cob becomes most aggressive when defending the incubating pen or young cygnets and will chase and even attack other wildlife and people nearby. Before leaving the nest, young cygnets may be subject to chilling during rainy periods and can die from exposure.