We have been watching a family of swans for some time. There were two adults and 7 Cygnets. The babies are now the size of full grown mallards, but they don't have flight feathers yet. Last week one adult and three cygnets disappeared. Do they separate to raise that many babies? The other adult has been "calling" and I have never heard a swan do that. I can understand predators getting the cygnets, but what happened to the other adult?