Robin

I think this is my first robin of the year, certainly of the season. He has been flitting around the elder tree all morning, trying to imitate the tits and chaffinches using the feeders, sadly unsuccessfully. I've also had half an eye on the rat on the peanut feeder! Advice about rats please. There is the saying that we are never more than a few yards away from a rat so should I just let it be, or should I be doing something about it?