Hi, thanks for your reply.
The parents' beaks are orange so I guess they must be mute swans.
The pond froze over last night and the swan was sitting on the ice in the middle. I put some food on the bank and chopped a hole in the ice but he didn't come over. He did, however, waddle over to the side of the pond, started running on the ice and actually got airborn for the first time (at least that I know of). He flew about 6 laps around the pond and came back down in the middle. Maybe he's just slower to mature. He was the largest of the babies and when they walked across my backyard to a smaller pond, he had to rest every few steps. He still has some dark feathers.
It is now warming up and raining. The pond will likely melt before it freezes for the winter so he should be able to feed for the next few days.
I tried sending a photo taken in July of the family walking across my back yard but the file was too large for your site to accept.
Maybe there is hope.
John