They have webbed feet and bills which are flattened to a greater or lesser extent. Their feathers are excellent at shedding water due to special oils. Duck, eider and goose feathers and down have long been popular for bedspreads, pillows, sleeping bags and coats. The members of this family also have long been used for food.
While the status of the Anatidae as a family is straightforward, and there is little debate about which species properly belong to it, the relationships of the different tribes and subfamilies within it are poorly understood. The listing in the box at right should be regarded simply one of several possible ways of organising the many species within the Anatidae.
Previously divided into six subfamilies, recent anatomical studies by Livezey (1986; A phylogenetic analysis of recent Anseriform genera, Auk 103: 737-754) showed that the Anatidae are better treated in nine subfamilies. This classification has been followed by Madge & Burn, Wildfowl (1988):
Five to seven genera with 23 species, mainly cool temperate Northern Hemisphere but also some Southern Hemisphere species, with the swans in two genera (three genera in some treatments), and the geese in three genera (four genera in some treatments):
Tadorninae: shelducks, sheldgeese and steamer-ducks
This group of larger, often semi-terrestrial waterfowl can be seen as intermediate between Anserinae and Anatinae. Recent revision has resulted in the inclusion of 10 genera with 23 species (one extinct) in this subfamily, mostly from the Southern Hemisphere but a few in the Northern Hemisphere:
The dabbling duck group, of worldwide distribution, were previously restricted to just one or two genera, but has now been extended to include 10 genera and about 55 species, including several genera formerly known as the "perching ducks":
The 16 species of diving ducks, of worldwide distribution, in 3 genera; Marmaronetta was formerly included with the dabbling ducks but is now treated here, and genetic analysis of the extinct Pink-headed Duck of India, previously treated separately in Rhodonessa, has shown that it is better placed in Netta:
