Praveen, I kept that secret thinking some should ask that question
Now you know how I got it !!
The tiny little water droplets of fog just infront of the lens go out of focus when the lens is focussed on a far off bird. The purpose of the flash was to get this effect from the fog than to light birds. The out of focus droplets when lit by flash will take this interesting shape. For me this gave an artistic appeal to the frame. I wanted to apply this technique to just the sky and birds but that was the last week of winter
No more foggy morning there after. May be next year..