Thanks for all your comments! The paper size is 27.9 x 35.6 cm, or 11 x 14 inch.
The bird is indeed a youngster, fallen out of the nest (after the picture was taken, the bird was put back into the nest again). The colour of these birds can vary, and this is obviously a very light coloured one.
I've added the final leaves and fluffy feathers to the buzzard. It's less obvious that what I thought/hoped, but I added some fine white ink lines at the top of the head to depict these fluffy feathers. If you compare with the previous version, you can see the difference.
Before I sign the drawing, I let it rest for about a week, and then decide if I call it done. At the moment, I think it is.