 Hybrids between the ruddy duck and white-headed duck are undesirable in parts of Europe where the introduced ruddy duck has bred with native white-headed ducks.The increasing number of ruddy ducks and hybrids threatens the existence of the white-headed ducks, resulting in shooting campaigns to remove the introduced species.This is controversial as some believe that nature should be allowed to take its course, even though this favours the more successful introduced species.