Yes, this is the normal winter molt. He is losing his old summer feathers so that new feathers which will be warmer and thicker can emerge for the winter. This molt usually occurs in one mate at a time so that there is always one parent to look after the cygnets. During the molt, the birds cannot fly and if they are able to circumvent the feather issue, will not fly very well. Nature will always have at least one parent available to fly and lure a predator away from the family or be able to fly quickly toward the cygnets if the young birds are in danger. The Regal Swan