An e-mail from Colin Butters;-
The difference in the colour of one cygnet could be that it is from a different brood & has lost it's parents, temporarily or permanently. You see this often in apparently large broods where they may be 7 plus young which would all not survive & some of them are different & certainly from different parents. I have seen this over the winter at Welney with their large flock, I believe of 8.
