Somewhere on the Wharfe

A friend who fishes regularly on the Wharfe told me about the friendly kingfisher he sees. This afternoon we went down to the river and after about an hour the kingfisher appeared. He was obviously used to people and let me get quite close, but even with a 400mm lens this shot is seriously cropped to get an image (not altogether as sharp as I would like) Any one out there know what size lens is required? Seems to me that even 600mm would not quite be enough.