Thanks for trying to help this bird , firstly if you can start to feed the bird in a certain spot on the garden and place a cardboard box above the food dish and support it with a stick on a bit of string then simply when birds eating under the box pull the string , bird caught then keep it in the box , then if you give us the birds ring number we will try to help you locate it's owner , it may also have a phone number on it's wing feathers