The best solution would be to return them to their original owner and make him place barriers (fencing or other items) to keep them in their original pond so that they do not "migrate" to your pond and threaten everyone.

Migration occurs during the nesting/mating season and they obviously like your area due to the readily available vegetation. If the original owner will provide them with a feeder and also supplementally feed them with lettuce, they would most likely stay in their original pond. However, if you start feeding them, they will not have any reason to return to their original pond.

The behavior you are describing is nesting/mating behavior and the hormone levels should abate within about 2-3 weeks. However, you want them to understand that you are the bigger swan and own the pond, not them. If you continue to permit them to chase you or other individuals without trying to control the behavior, the swans will take over the pond.

If you want to keep them around, then feed them and try to befriend the two swans. If they continue to chase, then you want them to get close enough to capture. Usually, capturing an aggressive swan will keep them from trying to get near humans if they think that they are going to be captured. Capture can be with a large net. Once captured, place the swans in a safe area, garage, shed or barn for a couple of days. Feed them and keep them on sheets to protect their feet. Once they are released back onto the pond, it is not likely that they want to get close to anyone as they will remember being out of water and their habitat. This usually corrects the behavior for some time. But, you need to capture both swans at the same time as you do not want to leave one without the other or predators could get to them. No guarantees that this would not happen, but two together can usually sound an alarm and help repel the encroacher. We hope this information is of benefit. The Regal Swan