At first glance you would think it was a Chaffinch, its difficult to get a scale of things from a photo, but take a good look, it is sat on a tea bag in my compost bin, so that may help give some perspective of size. Very small.i would say a baby chaffinch as a guess
most of the fluff will fall off as proper feathers develop. The colour of the fluff can be ignored
The light colour on the leading edges of the wing feathers suggest it is not a sparrow, but from the photo looks about sparrow size.
the legs and the shape suggests it is finchy
if it was taken recently, I doubt very much if it will survive the winter