The swans may have been blown in on the past extreme cold front that hit the country this past week. Sometimes, strong winds will blow the swans off course during their migratory paths. More than likely, the parents were showing this year's offspring how to make the migratory trek.

Since your lake has not frozen, the swans probably stopped over to refresh their energy and should go along their way in the next few days. If they stick around, it may be that your pond is the only unfrozen or partially unfrozen pond in the area and the birds have a water and food source for the winter, even if temporarily. The Regal Swan