I have always done a lot of 'action' photography, from high school sports to every imaginable kind of activity (lacrosse, anyone? Just try to find the lacrosse ball in the air!). Birds are tough, too, but birds as a subject don't interest me. I am very good at action photography. The problem with birds is that they are small, requiring huge lenses, and it's hard to keep them in the frame when diving and swooping in flight, with or without autofocus. Ever notice that most 'bird in flight' photos are of large birds? Their larger size makes them easier to photograph, since they can't change direction so quickly, and they glide more. Sparrows are almost impossible to capture in flight (other than just taking off from a perch). As you can see here, almost every one of these sparrow photos is of a bird perched. The very few that show them in flight are almost certainly taken with the birds approaching or leaving a known nest or feeder.
So, yes, I am more than qualified to offer advice. If anyone can take a 1000mm lens hand-held and follow sparrows in flight, I'll eat my words.