Gallinula chloropus (Common moorhen)

The Common Moorhen (Gallinula chloropus) is a bird in the Rail family with an almost worldwide distribution. It is often called the "Common Waterhen", especially in the British Isles, and this is a more descriptive name because the bird lives around well-vegetated marshes, ponds, canals, etc., and is usually not found in moorland. Another name, popular in the USA, is Common Gallinule. The bird is not found in the polar regions, or many tropical rainforests. But elsewhere the Common Moorhen is likely the most commonly seen Rail species to most people, excepting the Coot in some regions.

A "watercock" is not a male "waterhen", but the rail species Gallicrex cinerea, not especially closely related to the Common Moorhen. "Water rail" usually refers to Rallus aquaticus, again not closely related.