which is further split into a varying number of tribes. The largest of these, the Anatini, contains the 'dabbling' or 'river' ducks – named for their method of feeding primarily at the surface of fresh water. The 'diving ducks', also named for their primary feeding method, make up the tribe Aythyini. The 'sea ducks' of the tribe Mergini are diving ducks which specialise on fish and shellfish and spend a majority of their lives in saltwater. The tribe Oxyurini contains the 'stifftails', diving ducks notable for their small size and stiff, upright tails. A number of other species called ducks are not considered to be 'true ducks', and are typically placed in other subfamilies or tribes. The whistling ducks are assigned either to a tribe (Dendrocygnini) in the subfamily Anatinae or the subfamily Anserinae, or to their own subfamily (Dendrocygninae) or family (Dendrocyganidae). The freckled duck of Australia is either the sole member of the tribe Stictonettini in the subfamily Anserinae, or in its own family, the Stictonettinae. The shelducks make up the tribe Tadornini in the family Anserinae in some classifications, and their own subfamily, Tadorninae, in others, while the steamer ducks are either placed in the family Anserinae in the tribe Tachyerini or lumped with the shelducks in the tribe Tadorini. The perching ducks make up in the tribe Cairinini in the subfamily Anserinae in some classifications, while that tribe is eliminated in other classifications and its members assigned to the tribe Anatini. The torrent duck is generally included in the subfamily Anserinae in the monotypic tribe Merganettini, but is sometimes included in the tribe Tadornini. The pink-eared duck is sometimes included as a true duck either in the tribe Anatini or the tribe Malacorhynchini, and other times is included with the shelducks in the tribe Tadornini. Morphology The overall body plan of ducks is elongated and broad, and they are also relatively long-necked, albeit not as long-necked as the geese and swans. The body shape of diving ducks varies somewhat from this in being more rounded. The bill is usually broad and contains serrated pectens, which are particularly well defined in the filter-feeding species. In the case of some fishing species the bill is long and strongly serrated. The scaled legs are strong and well developed, and generally set far back on the body, more so in the highly aquatic species. The wings are very strong and