Sure, I'll share my "secret" settings.
For birds against a blue sky I use the center focusing point plus the four auxiliary points. For birds with trees or other items in the mid-ground I use center point only.
A couple of other tips. I always use H1 Servo and I have the autofocus set to "quick mode." I also configure the autofocus to "continue to track objects, ignoring possible obstacles."
One more tip. Be sure to set the limiter switch on your telephoto for the appropriate distance. Setting for the closer setting means that the lens will "hunt" to find focus and take longer to lock on.
With all of this, it's still a hit or miss affair much of the time. It's a lot easier on a sunny day, with a blue sky for a background. It becomes really difficult to capture birds in flight when it's overcast and/or when the background is cluttered.