The sight of two male swans fighting is unsettling. However, this is nature and eventually, they will settle it among themselves. Yes, sometimes deaths can occur due to an errant wing strike causing internal or neurological trauma. Usually, there is slight physical injury but major injury to pride which is the declaration of dominance. Your intervention may help from physical injury, but eventually, they will still have a fight. Think of a school yard fight. Until something is settled, the two combatants will keep trying to settle their differences no matter how many adults or others intervene.

Do not blame the dominant male. He is only protecting his family. If you hurt him, the cygnets and his mate will be in extreme danger to other swans and predators. Once nesting and rearing of cygnets are completed, the testosterone level of the males will drop and things should return back to somewhat normal. The Regal Swan