If you can keep the swans indoors during severe winters, it will be better for the swans in that an indoor shelter will protect them from predators, drowning, and susceptibility to disease from being cold or wet. You would need to provide them with food, free from pests such as ants and mice, placed on a non-slick substrate such as straw, which must be mucked daily. As long as the swans are warm, placed in a ventilated area with no direct draft, sprinkled daily with warm water to maintain the health of their feathers and keep them water repellent by making them preen and dry themselves, given a good watering down with warm water at least 3 times weekly, they can stay indoors for the winter with no problem. They cannot stay outdoors on land during the winter as they can be accessed by predators and inclement weather such as too cold, too windy or too wet can leave the swans unable to keep dry and warm.

If you keep the swans on the pond during severe winters, you must keep the water open so that the birds cannot fall in, drown because they cannot exit the water for be stranded on the frozen pond and be attacked by domestic or wild predators. The Regal Swan