Nikon AF-A or AF-C

I use Nikon D90 with 70-200VR+2X lens. I believe the default setting of that camera is AF-A. I usually shoot using the AF-C setting in P mode. And I usually shoot handheld with occasional use of a monopod. I shoot only birds. Assuming I am photographing a small skittish bird (frequent movements) would AF-C be the best camera focus setting? What would be the preferred focus setting for a relatively stationary bird, or for one in flight? I try to use the "square" in the middle of the viewfinder to zero in on a shot. I am not concerned about framing. If I get the bird sharp and complete anywhere in my final image I'm happy.

Thanks,
Wendell

Wendell,
I use AF-C 90 + percent of the time because like you I photograph many moving subjects.

If I photograph a static subject, I use the AE-L/AF-L button on the back of my camera. I focus on the subject, press the AE-L/AF-L button and re-frame.
The camera will not attempt to re-focus as long as the AF button the depressed.


Program the AE-L/AF-L button via Custom Settings Menu F4 (I think)

James, thanks, your reply is helpful.