Wild birds are ringed to help us understand more about their movements and survival. Metal rings on wild birds have an address and a ring number.  The address tells you which country it was ringed in and the number is a a unique identifier. The UK address is frequently the Natural History Museum in London and the ring number is most frequently one or two letters and a series of three to six digits. Make a careful note of the number. You can report the find online at http://app.bto.org/euring/main/ and if at all possible provide the grid reference of the place at which you found the bird. The British Trust for Ornithology will let you know where and when it was ringed.  British records are normally provided within a few weeks; some foreign ringing schemes may take longer.