Roshan, that is a trade secret!
Well, let me share it here! Kiran asked me the same question. Here is how it is made.
The backdrop you see is bamboo thickets at Ranganathittu Bird Sanctuary. Some are bent right, some left which forms the vertical/slanted lines. It may be more evident in the color version (check
this link ).
Kiran, about the texture, it is a new invention
This is a result of a series of experiments I conducted during last monsoon (
some more images here). The idea is to accurately pan when the bird flies very close to backdrop. It needs some good practice to accurately pan the subject (and a good pan head).
Now a question to you all, why we need a bird flying close to backdrop? What changes if it does not from overall effect of the image?