One of the two adults is harassing one of their cygnets by chasing it and pecking at it. The cygnets are just changing colour to white. The season is the start of winter. Is this natural? Why is only one of the five cygnets being harassed? The other adult and cygnets are nearby.

Every year the two adults have cygnets and they eventually go somewhere but I didn't see this before. I feel sorry for the cygnet. It must be exhausted.