Thanks very much. Oddly, yesterday we thought we might have seen some other cygnets, but having gone right round the lake (it's very small) we could only see the parent ones. They would be quite large now, and the father is now spending his time with the mother, but I guess they could be hiding away on one of the islands. Otherwise it may be as you say, that she wasn't very good at looking after them, although she was being very protective of them when we saw them. There is quite a lot of predation locally from foxes and probably cats. I think foxes could easily swim to the islands, which are very close to one shore. It's been a bit disappointing at the lake, as our first pair of nesting grebes disappeared without any fledging, although our Canada geese and mallards are breeding prolifically.