Swans are built for cold temperatures. Maybe, the freezing of the pond was a one time occurrence and nor a usual event. Even so, swans, especially in captive settings need shelter (i.e., indoors such as shed, garage or room) in extreme wet cold temperatures as well as supplemental food. Is someone caring for them or do you know who owns tgem? The pond needs an aerator/de-icer to keep the pond open. The owner/swan keeper needs to know the above information to keep the swas safe and healthy, especially for captive swans during the winter months. The Regal Swan