Thank you for all of this useful information!

This is a very strange story, to be honest. I work in a park. Every year we have ducks and a few swans in our ponds (we don't have swans every single year, but they use our ponds pretty often). I thought that they all had flown away a long time ago, like they do every year, but several days ago we found an adult mute swan. I have no idea how he'd even managed to survive. First, all of our ponds have been frozen over for a while and, second, we've been having a cold winter (about -20 oC). I think he'd been living on one of the small isles some of our ponds have, but there's no way to tell. Still, without water and food it seems very odd that he's alive.

At first we thought he was just too cold, because he moved stiffly, but then we saw one of his wings hanging limply. He seemed too tired to resist or try to escape when one of our workers tried to lift that wing, and it was clear that the wing was damaged somehow. We don't know any avian specialist, since our birds are always on their own and aren't domesticated or anything like that, so we simply found a vet who used to work with domestic birds. The X-Ray was taken. The break is clean, but both bones are broken. The vet gave him some medicine and bandaged the wing to the swan's body; the bandage still holds. The swan eats and drinks, and we've placed him into one of our buildings in the park that is relatively warm.

As far as I know, in my country there are no laws that require a swan to be killed or euthanised in any case, and our park has no predators (an occasional cat notwithstanding), so, basically, everything is up to us and no service would interfere. But it still means that, if the swan won't be able to fly again, we'll have to arrange something for him to survive our cold seasons, which is why I decided to ask your opinion. The vet said that there no way to tell just yet, but I don't think he's very experienced at restoring wings so they would work like before if possible (I imagine, domestic fowl he used to work with doesn't have this sort of requirement anyway).

I asked about the flight feathers, because the vet wanted to cut them at first to make the wing less heavy for the time being, but then he decided against it, for some reason.

We keep an eye for the swan's mate, but, if he has one, he or she isn't in our park.

Thanks again for replying!