Ask the Swan Specialist
Date: 31 March 2016
Give it a few weeks, if not days, and the parents will intervene and chase junior out of the habitat so they can start another brood. The "aggressiveness" may not actually be such, but rather trying to mate with the mother if it is a male. The young bird is having its first rise in hormone levels and does not know how to control himself. Again, all of this will behavior will return to normal within the next few weeks.