If the cygnet can fly, and these are not his parents or the parents are telling him to get lost, he should be fine. If he is not old enough to fly and these are his parents, he should be fine. If these are not his parents, they could chase him, but hopefully, his parents are not too far, they will find each other. There are just too many variables in this situation to know why the cygnet was on the side of the road, etc. to determine how this is going to turn out. The Regal Swan