Ducks, geese and swans are adapted for swimming, either floating on the surface or diving. Most have webbed feet set well back on the elongated body, and waterproof feathers. Most are herbivorous, and many are strong fliers that undertake lengthy migrations. In many species, the male is brightly coloured. Many species are kept for ornamental or culinary purposes and, as a consequence, escaped or feral birds and hybrids are often encountered.