He is lovely.
Give him plenty of water and food to give him more energy. You can add some of you chicken food as he will like that.
His shape and colouring look like he could be a feral pigeon. Usually pigeon owners will ring their birds. It does not make any difference as even a feral pigeon will make a great tame pet.
If you want to keep him then I would recommend you treat for parasites, as feral birds often have many.