Mark Cocker in 'Crow Country' tells of a few tales of how rooks have acted to come to the aid of nature and man. Some are very interesting. In 1891-3 in south-west Scotland there was a plague of voles. A plague of biblical proportions. It was only stopped when a huge number of rooks attacked and killed thousands. A committee appointed to inquire into the origins of the plague concluded that over-zealous control of predatory birds like rooks may have been responsible in the first place.