Some parents, no matter the species, do not make good parents. He just may not be able to deal with kids and they are a nuisance and unfortunately, this is how he takes care of them. Now, on his defense, if he has some genetic anamoly in his genes that is producing defective cygnets, he will kill them if he knows something is wrong with them. Unfortunately, this is nature and you could intervene by taking the cygnets away at 3 weeks of age and sending them to a waterfowl rehabilitation center or do nothing. The other possibility is to remove him and his mate from this area and give them another good home. There may be something else in this particular area of the habitat that may actually be killing his cygnets and not him, i.e., soft-shelled or snapping turtle, fox or other predator.

Because he has ponded, you should not break the pair up because this would not be fair. However, by removing them to another area, he may become a better parent because he is not so territorial. We hope this helps. The Regal Swan