American and European Coots

Below are some photographs of American and European Coots, they're very much alike, but there are subtile differences.  The first three photographs are of American Coots.  There's a real difference in the amount of white on the forehead and a distinct dark mark near the base of the American Coot, which is not present on the European species.  The American Coots shots were taken in Texas, the European ones at various places in the UK.