In days gone by one of the delights of the English language was the profusion of colourful collective nouns used in everyday life. But, as our lives become ever less connected with our rural past, many of these treasures are being lost and we tend now to believe that all birds belong in flocks. Many of us still remember "A murder of crows" purely because it is so unusual, but how many recall "A herd of mute swans"?