Swans are protected throughout the UK especially their nests and young. There are two options: contact the local RSPCA to see what they can do or shut down the particular hole and play another hole twice. Any disturbance to the swans or nest can bring criminal charges so playing another hole seems to be the best solution. Penning the birds prevent their access to water unless a pond is within 10-15 feet and a pen or barrier could be erected. However if a pen is used it must have access to water and be 1/2 on land 1/2 in water with a feeder inside. The pen must be completely enclosed to prevent predators from digging under or climbing into the pen. Furthermore, the bottom of the pen from ground level to 4 feet high must be lined so the cygnets cannot get out of the pen. So, as you can see, avoiding the hole is a much simpler solution. The Regal Swan