The crop is proportionate from all sides as this is the composition I wanted. The reason for the crop was a small branch entering into the frame from the left side.

I didn't dial any exposure compensation. I knew about the bright spot (sky) in the background. Ideally I would have liked to move a bit to the left so that the spot is hidden behind the bird. However, didn't ask the driver to re-position the vehicle for fear of disturbing it. After this shot it actually flew to another tree. Also, I didn't want the bird to be seen too close to the tree branch on either side. Moving to the side would have resulted in that. Also, it was an overcast sky, and the bright spot in the background was not very bright. On a sunny day, the difference would have been huge.

I had used the 1.4x II TC instead of the 2xII TC thinking that the light was low. With the 1.4xII TC I was getting a focal length of 560mm at f4. And with the 2xII TC I would have got the focal length of 800mm at f5.6. However, in this case I photographed at an narrow aperture of f9. The reason was to capture the details in the bird as well as the texture in the angled branches. I hadn't taken the bean bag along, but was confident that I can pull off a sharp image just by resting the lens on top of the rod on the roof of the jeep.

I often ask people about the amount of crop and I am told that some people feel shy about mentioning it. If so, one can calculate the amount of crop by this formula and then see if the resulting image is sharp or not. That will also be a pointer to your technique.

Cheers,
Sabyasachi