Here is the updated version. Soft shadows enabled (default settings). I think it's just enough soft. More blurring would look unnatural.
To reduce rendertimes I slightly decreased the quality settings of the render (from Det/AA 0.5/6 to 0.4/4). It took only 19 hours to render without being too noisy I think.
Additionally I added some more birds. I wanted at least one of them flying in a lightbeam casting a shadow in it. Took some time to place it, until it worked.
Thanks again Ulco for the soft shadow suggestion. It really looks more natural I think.