Have you ever had the unsettling feeling that you are being watched? This Bald Eagle must have had that feeling as I observed it through 300mm F4 + 1.4xTC. At the same time I got the impression the eagle had a better view of me than I had of it, thanks to its' superior eyesight. The Eagle would stop and look at me each time the mirror of my D300 slapped back into place after a shot, which was nice because I got shots with it watching me, but at the same time I didn't want to bug the eagle either. As I walked away after shooting the eagle for a few minutes, it flew off. I think I overstayed my welcome, which is too bad, because I try my best to observe, but not disturb my subjects.
There are warning signs that you are disturbing your subject when shooting wildlife, first being that they stop what they are doing and watch you intently. If the creature starts to do that, refrain from any sudden movements because that causes them stress. I hope that the eagle I was watching spotted something tasty across the grass field rather than being stressed by my presence, but there is no way to know for sure.