The difference between Moorhens and Coots

Coots are black all over, except for a pure white shield extending up the forehead from the bill to the crown. ‘Bald as a coot’ is a misused expression; a man so described isn’t bald. The top of his head is bare from the forehead upwards, but he has hair at the sides above the ears.
In their sombre clerical dress, lacking the gaudy glamour of ducks and grebes, these water birds seem dull and colourless.