Identity Crisis - Duck or Not Duck?

I went for a slow amble around Lochore (Fife) this afternoon.  It took longer than I expected because of frequent stops to check out things that caught my eye.  I only realised just how long I had taken when people I passed started saying "Good Evening" instead of "Good Afternoon"!

One thing that caught my eye was a grey lump amongst sleeping mallards.  It was bigger than them and I coudn't decide what kind of duck it was.  All suddenly became clear when it stirred and turned its head to reveal itself as a grey heron, Ardea cinerea!

I have never seen a heron resting in this manner and searching on Google only showed similar images by two other individuals - none in the presence of ducks.

Excuse the quality of the photo as it was far away.  I had to go beyond full optical zoom into 2X digital zoom and even then, this is a crop.