Nice shot, with the context including reeds of the sort the bittern uses for disguise.
I worked it a bit more to show more of the bird, less of his surroundings, but you are quite correct in how well one of these guys blends in with his surroundings. I had to look twice after I first caught a glimpse of a movement in the water's reeds before realizing there was a bird there. Like most predatory waterfowl, stealth and disguise are it's best allies.