SWANS.
These large and handsome birds form the small but well-defined sub-family Cygninæ. They may be distinguished from all other species in the Anatidæ, by having the lores, or space between the eye and the base of the bill, bare of feathers, and by their reticulated tarsus. In this sub-family, as in the Anserinæ, the sexes are nearly alike in colour. Swans moult only once in the year, in autumn. The young birds—known as Cygnets—are hatched covered with down, and able to swim. In first plumage they are uniform grayish-brown; and, unlike the Geese, they appear not to undergo any moult during their first autumn, but after the moult, which takes place in their second autumn, they acquire the pure white plumage of the adult. Although this sub-family contains but seven species, probably all referable to one genus, its distribution is wide, embracing the Palæarctic, Nearctic, Neo-tropical, and Australian regions. Besides the Mute Swan, two other species are British, in the sense of visiting our area to winter.