Swans are the largest of all waterfowl. They eat sub-aquatic foliage that it can reach under water using its long neck. Black swans are mostly black. Some of the wing feathers are white. They also have reddish or pinkish irises and richly colored red bills with a white line. The juveniles are greyish brown with light tipped feathers and a lighter colored bill. As with many birds, there is sexual dimorphism where the male (called a "cob") is slightly larger than the female (called a "pen"). When they are fully grown they have a length of 110 to 140 cm and weigh between 3700 to 8750g. The wingspan ranges between 160 to 200cm. Black swans live in lakes, rivers and swampland, which can be fresh, salt or brackish water. They prefer habitats with aquatic vegetation. While their natural habitat is aquatic they are sometimes found in terrestrial areas such as dry pastures or flooded fields when food is scarce. Black swans are monogamous and often have the same mate for life. Both male and female black swans incubate the eggs. Chicks are precocial and can swim and feed soon after hatching. They may ride on their parents' backs when they venture into deep water. (Source: University of Michigan, 2014.), (Image: Kim Wormald).