This totally depends on the individual swan. Most male swan parents will protect the cygnets and their mate, but males are not going to carry the young around on his back for them to rest. He is not going to sit on top of them to keep them warm in the nest at night. So, if the female swan has been killed, it would be better to go ahead and collect the cygnets and raise them with other juveniles or cygnets such as in a waterfowl rehabilitaiton center or a reputable breeder. The probability that the cygnets will survive with just the male parent is not very high.

It is also very important that the cygnets be raised with other cygnets or at least them are kept together so that they will understand that they are swans. If the cygnets are separated and are raised alone, they will imprint on their human caregiver and it will be extremely difficult to provide the imprinted swan with a safe secure home. Imprinted swans will go up to anyone and anything (including pedators). This is why they can never be placed in a situation other than with the individual that raised them or someone who understands their need for constant supervision. The Regal Swan