Rockery worker

We quite often see a Wren methodically working its way along the rockery and garden walls pecking away at what we presume are grubs within mossy surfaces. As these little birds are constantly on the move, I find getting a shot is very difficult. However, this one paused in front of the lounge window when the camera was focussed, but the double glazing tends to blur the picture somewhat - it must be due to dirt on the windows caused by all the rain.