oh - i was under the impression you were asking about inflight shots... but yes hunting autofocus on branches is annoying... that is where intimate knowledge of your lens is needed to know how to switch off AF quickly and without taking your eye from the viewfinder  ;)

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

Rich Meadows Photography