Peter Collins, the National Trust warden in the area, said: "This has to be the work of someone with a very sick mind. There have been problems with air guns in the past, but this has a definitely sinister element. It is the most disturbing and barbaric incident in more than 10 years." He said the birds would have been sitting targets as they were protective of their nests and would be reluctant to move.
David Hirst, of the RSPB, said anyone convicted of the offence could be fined up to £5,000 for each dead bird and/or face jail for up to six months under the Wildlife and Countryside Act.
The colony which is over 70 years old comprised over 5,700 pairs at its peak but during the 1990s declined to as few as 2,300 pairs. Today's slaughter will only hamper any hoped for recovery.
Police are hunting the gunman.
