We are sorry for your loss. Regardless of cygnets or not, you need to round up the female and the cygnets at night. How was he killed? Predator? If so, the predator will continue to return to finish the rest of the family as an easy meal.

You can safely keep the family in a garage (as long as there are no chemicals, gas fumes, etc. Then, return them to the pond an hour after sunrise and return them indoors an hour before sunset. Sunset and sunrise, and throughout the night, most predators roam in search of prey.

If your pond is surrounded by wildlife habitat with predators, you may need to keep them in an enclosed barn or other enclosure so that predators cannot get to them. Or, you can build holding pens, chain linked fencing half in the water and half on land with a feeder inside. You can teach the swans to come in at night, close the gate and then return them to the pond in the morning. The pen must have a chain link fence covering on top so that predators cannot access the pen from above and poultry fencing placed on the outside perimeter so that predators cannot dig under the fencing. The bottom of the fencing should have plastic poultry fencing or fence slats going from the bottom rail up about 4 feet. This will prevent the young cygnets from leaving the pen through the chain link fence and getting out of the pen and separated from the female parent. In other words, make sure that the outside perimeter of the fencing is covered sufficently so that the cygnets cannot go through the open diameter of the fence or get their necks or heads stuck in the chain link fencing.

If the swans continue to stay out on the lake at night and there are predators, both domesticated (cats, dogs and humans) or wildlife, they may succumb to the same fate as the male parent. The Regal Swan