These birds are distinguished by their swimming powers and corresponding organization. Legs usually set on far back, shorter than the body. The feet in particular are adapted for swimming. In some swimming-birds each of the forwardly directed toes has a webbed margin (“split swimming feet,” Fig. 43); in others, the three front toes are all united by a web (Fig. 44), while the hind toe is either small or wanting (“swimming feet”); lastly, there are some in which all the toes are forwardly directed and united by a common web (“oar-feet”). The plumage of swimming-birds is compact, and always kept greasy by the secretion of the oil-gland. I shall speak of two families only. Family: =Lamellirostra= (_Ducks_). [Illustration: FIG. 43.—Crested and Little Grebes (_Podiceps cristatus_ and _minor_). ] The inner margin of the beak is covered by skin, thrown into transverse ridges or tooth-like projections. Swimming feet (Fig. 44). Tolerably long wings; remarkable powers of flight. Feathers soft. These birds mostly affect shallow fresh water, in which they get their food by grubbing in the mud, the soft skin of the beak serving as an organ of touch. Polygamous. Young precocious (p. 51). Here belong—the long-necked =Swans= (_Cygnus_) and the thick short-necked =Geese= (_Anser_), in which the beak is higher than broad at its base; the =Swimming Ducks= (_Anas_) with broader beaks, the =Diving Ducks= (_Fuligula_), and =Goosanders= (_Mergus_) with a broad hanging web to the hind toe. None of these birds are useful, while wild geese and ducks are harmful. [Illustration: FIG. 44.—Goose (_Anser cinereus_). ] Three species of wild =Geese= (=Grey Goose= = _Anser cinereus_, =Bean Goose= = _A. segetum_, =White-fronted Goose= = _A. albifrons_) chiefly breed in Eastern or Northern Europe, and only come to Britain in autumn or winter, flying about in flocks. They eat the grass in low-lying meadows, and even pull it up by the roots; in the cultivated fields they devour winter corn and winter rape, and tread down more with their clumsy feet than they eat. They are also harmful to vegetable growth, owing to the very caustic nature of their dung, which is often deposited in large quantities in one place. In regions where they breed they also devour both ripe and unripe grain. Where they only occur in autumn, they scrape potatoes, turnips, and carrots out of the ground in order to eat them. Flocks of geese fly in a slanting line or in the form of a ploughshare.