It would seem that they have a nest somewhere in the barn and she is sitting on the eggs. This would be normal behavior for not wanting to leave the nest/eggs. If this is the case, you need to provide them with a flat tray of water and food (1/2 cracked corn 1/2 layer pellets and chopped lettuce). This will be the same food that the cygnets will eat when they hatch. The pan must be flat enough so that the young birds can climb in and out without hurting their legs or feet. You must keep fresh food and water in the barn and check for pests such as ants and rats. You also need to close the barn so that predators cannot access the birds. If you check around and the swans have no nest, then yes, you need to get them to stay in the pond. If they choose to come back to the barn, you can train them to stay on the pond during the day and staying in the barn at night for safety. Same for nesting. The Regal Swan