Quote Originally Posted by Sabyasachi Patra View Post
Udai,
It becomes more difficult to track your subject, leave apart a moving one, as your focal length increases.

In flight photography, focus acquisition is a tricky task. It is better to prefocus at a point where you anticipate the bird. When the bird nears that area, just press your shutter button and the bird comes into sharp focus. You can then take your picture.
Thanks Sabyasachi. I will try this out.