Before, the young swan may not have had any other potential mates. Now, that there are other swans on the lake, this male will eventually try to become the Alpha Male. Therefore, in normal wildlife circles, there can only be one Alpha Male and the older male needs to go in their eyes. So, either he subjects to being the low man on the totem pole or he will be beaten/possibly injured or even killed if everyone jumps on him. He may also become very stressed in that he cannot enter the water to feed or bathe or exit the water in areas where he needs to preen and get dry. This stress can actually cause him to become susceptible to disease or illness. Place him in the pen (ensuring that nothing can dig under or crawl into the pen to access him-i.e., predators) and see if the aggressive behavior against him subsides. This issue may just be occurring during this time when the sex hormones for mating and nesting are at their highest. Give it a couple of weeks, see if it subsides when everyone’s hormones settle. If not, you may need to find him a new home. The Regal Swan