The swans are some of the largest flying birds. They are large in size and have large feet and long necks. The males are usually bigger and heavier than females. The mute swan, trumpeter swan, and whooper swan are the largest swans. They can be over 1.5m (60 inches) long. They can weigh over 15kg (33 pounds). Their wingspans (this means the length of both wings) can be almost 3m (10 ft). 