Back button AF question

Read the threads on this subject and want to give it a try. A bit of confusion on my part. In tracking a bird in flight, in servo, I get it in the frame and hit the button and keep pressing,focus and start shooting. If I can't keep up and the bird is lost in the frame should I release the button and then refocus once it is back in the frame? Would it be alright to just keep pressing the button until the bird is back in the frame? It seems that would drive the AF crazy, trying to find another subject. Another thought would be if I keep pressing it until the bird is back in the frame, will it refocus faster than releasing the button once I have lost the bird in tracking and then am able to reframe the target and refocus? I told you I was confused. This whole thread is confusing me as I reread it. I guess simply put, hold on or not. Thank you for your help. By the way, if you are reading this and haven't tried birds in flight, give it a try. I find it very challenging frustrating and exciting. Can't wait to review and see what has just happened. Sometimes it's "Cool", sometimes "Pretty good", but a lot of times, "Screwed that opportunity all up". Part of the allure.

Based on my limited experience, I would imagine that the distance of the background directly behind that bird would play a big role in deciding that. I would assume that in most cases, the background will be very far away. If thats the case, keeping AF on would cause the lens to zoom towards infinity and back, trying to latch onto something, making it so that once you reframe/compose your bird shot, it will have a longer focusing distance to travel and take longer to re-focus on it compared to if you just let off on the AF button. (That is unless he's flying straight at you, heh)

Perhaps this wont matter as much if you have a really good lens? The lens I use the most right now (50mm 1.8) makes sooo much noise and takes years to focus (even on a 7d) that I might not be qualified to speak on this subject.

You release from focusing to catch the subject again. If you keep focusing as you try to recompose the subject (nay, find it again in frame) the focus will be looking all over the shop.

Letting go to regain you subject means that the focus will be in the vicinity of the subject (at the point it was lost) which is preferable as it will, once the subject is regained, snap to focus faster than if you have been pushing e focus around all over whilst trying to find it again.

I actually find it beneficial to tap the back button while finding a bird in flight.
its not necessary but its something I do and other do.
(it may just make me feel better. LOL)

but yes, let go of the button if you lose the bird. then hold it when you find it again.

Definitely let go and then re-press when you regain the composition. And then, other factors are whether you are using a selected focal point or all points. With a selected focal point you want to make sure that you get focus using that point. With all points, in AI Servo, use the center point to regain focus.

But this has nothing to do with Back Button Focus, the same would apply with shutter button focus!