Shelducks are mid-sized birds that fall neatly between ducks and geese. With a particularly prominent red bill, black-green head, and chestnut and white upperparts, shelducks give the impression that they couldn't quite make their mind up as to what colour they wanted to be. When flying they typically look heavy and have slow-beating wings.

Shelducks favour dense gorse and bramble patches, and hollow trees for nesting sites. Once young birds have hatched they will be lead almost immediately to a nursery pool, which may be some distance away. Here shelducklings will form large crèches and be looked after by non-breeding adult birds. Once the young birds have settled in their parents will leave, heading off to a moult gathering (a kind of end of season party with a guest list of thousands), where they will sometimes stay throughout the winter months. Others will join in an autumn migration, where thousands of birds can be on the move together while traveling in groups of a hundred or more.