Swans are considered some of the biggest birds in the waterfowl family. They are related to geese in the subfamily Anserinae. The most common swan is called the mute swan. It's big and white with a black knob on the top of its bill. Swans can live up to an old age of thirty years, and individuals usually mate with the same swan throughout its life.
Adult swans can grow to an average of 125-155 cm long with a 200-240 cm wingspan. They can also have up to 25,000 feathers. They are one of the largest and heaviest flying birds: the males can weigh up to twenty-seven pounds and the females up to twenty pounds.
A male swan is called a cob, the female is called a pen, and their young are called cygnets. A swan will mate with the same partner its whole life, and will only switch to another partner if the male is unable to build a good enough nest for her eggs. They usually have up to three to ten cygnets at a time. Incubation lasts for 35-40 days. When the eggs hatch they start out having grey plumage and then as they mature they will get brighter in color. They guard their eggs and their territory, each taking turns sitting on the eggs. When they feel threatened they lower their heads and hiss to tell the predator to back off.  
Swans that have white plumage live up in the Northern Hemisphere, and swans that have dark or black plumage live more in the Southern Hemisphere. Most of the swans species have grey feet but only two species have pink feet. They basically eat any vegetation floating around in the pond they're in. They don't have a really nice sounding call, but instead they have a loud annoying honking sound, as with all the geese species.