Thank you for the helpful reply. I gather this not work in Servo AV which is what I need for moving birds. For this Servo AF case I will just have to use one of my adapted EF telephotos.
The trick... IMO is to use back button focus. I keep the camera in servo mode 90% of the time.
So, here is a scenerio.
Bird in the brush. Doesn't matter which camera you have it isn't always something that goes as you want, and overriding the system is definitely useful. Camera settings. Small AF point, servo mode, continuous.
1. Place AF point on the bird.
2. Press BBF to AF & half press shutter button.
3. Adjust exposure if needed (if I have time, and my settings are too far off in terms of exposure).
4. Take the shot.
This is the ideal scenerio.
Alternative (happens more than I like).
At step (2). Focus lands on a background of foreground object.
Case 1.
a. Let go of BBF, and immediately turn the focus ring to override the focus. As long as the camera is metering this is possible. As as BBF is not held down the camera is not doing AF and thus I can do MF.
b. Rack focus and fire off a burst. Point is to try to get at least one image in focus.
Case 2.
a. I press the button I have assigned to toggle between one-shot and servo.
b. Perform MF and do the same racking focus.
But why switch to one-shot? Because I have that set so that after initial focus is achieved (green box) if I keep the BBF pressed in, when I perform MF I get the magnified view. I find this useful for an animal that is not moving around too much. And it allows me to get critical focus.
The only reason why I like having an AF/MF switch though, is that when switched to MF then the focus assist kicks in (the 3 triangle thing). But in my experience the feed back it gives you is the same as if the camera as doing AF. But it is nice to have at times.
Sorry for the rant.