Sparrow with a ring !!!

I keep an eye on the bird feeder daily and have had this chap come on a daily basis as he is part of a group of about 30 sparrows that frequent the garden ..... but he has a ring ..... I didn't realise that sparrows got ringed ... this seems to be the only one but I have recorded him since the 23rd January ... anyone else seen a ringed sparrow or know anything about them ?? .....