Is it injured so you could catch it to read the ring? You can get the information about who owns them from the internet, though I doubt that they would pay up!
We have Sid who was hit by a car 6 years ago, I brought him home to have a peaceful death as it looked imminent!
He now fit and healthy but with his broken wing he can only flutter, he lives in a greenhouse with a lot of ventilation to keep him cool, and shares it with Tomatoes in summer which he carefully defoliates to try and make a nest! it's amazing how resilient tomatoes can be with the abuse they suffer!
