WHITE (mute) SWAN

At the beginning of the breeding season last year I was surprised to find a white swan on the Christchurch Ponds. About 3 weeks ago I found this number had increased to 5.  Hidden family development has been going on in the bushes with three youngsters now joining the family. We havent seen white swans here for a number of years. Will they stay is the question?
Rgds IK