Roy C
Occasional bird snapper
Yes you can Peter but recomposing always runs the danger losing the critical focus point if you are fairly close to the bird. The DOF is fairly small with long lenses so you are depending on the re-composure being precisely on the same focal plane, if you move forward or back a slight amount then critical focus could be lost. Having said that this is often what I do but I always take a burst to heighten the chances of nailing one.Surely you can use your thumb to focus, take your thumb off, recompose and fire the shutter. I thought this was the major benefit of back button focus?
I would not say this is the major benefit of BB focusing though, for me it is the ability to switch between AI servo,pseudo one-shot, and manual without changing anything. It is also very good for 'pumping' the focus for flyers when you lose the bird.