Camera Setting Tips for Action Shooting
First, there is no combination of camera settings that is ideal for every shooting situation, and not every camera has the same capabilities. So given that, let's cover the concepts that will help you decide how best to set up your camera for shooting moving wildlife with a telephoto lens and the PGD Tracker optical sight.
Shutter Speed: The usual rule of 1/FL as a minimum shutter speed, (1/600 second with a 600mm lens, for example), is probably not going to get you the razor sharp images of birds in flight that you desire. Assume half that, 1/1250 sec, as a starting point. A gimbal mounted rig will be a bit more forgiving than shooting freehand, but faster is always a safe bet.
Aperture: The f-stop controls the DOF, (depth of field). DOF is often thought to be only of concern to landscape photographers, but at a subject distance of 50 feet a 600mm lens at f5.6 has a DOF of only 8". A large bird might not be be sharp from wingtip to wingtip! A larger f-stop will increase DOF, but further starving the sensor of light means forcing the ISO up to get the exposure. The latest sensors are producing useable images at increasingly high ISOs. This is very camera specific, so you have to determine the highest ISO that gives you acceptable results.
ISO: If you choose to set both shutter speed and f-stop in Manual Mode, then the last piece of the exposure trilogy is ISO. You can set the ISO to get the proper exposure for a given shot, but this is likely going to result in over or underexposed images with changes in lighting. Most newer cameras now have an "auto iso" setting, which might be a better choice for consistent exposures. One caveat is to take a few test shots to decide if the ISO the camera chooses is satisfactory in terms of image noise.
You might have to dial back the aperture and or shutter speed to control the noise of high ISO, but remember that a sharp noisy shot is far preferable to one that is not sharp. Good noise reducing software is your friend!
Auto Focus and Focus Patterns: If you are not fully familiar with your camera's options in this regard, pull out the manual and read up! A option often preferred by professional shooters is "back button" focus. Typically activated by the right hand thumb, it allows full control of when the AF is on. For fixed targets it allows getting focus on the subject and then recomposing the the shot as desired. For moving subjects, holding the button on while shooting keeps the AF working while the subject distance is in flux. Choosing the "continuous AF" or "AI Servo (Canon), or whatever your brand of camera calls it, is the best for moving targets.
Most cameras now offer a choice of AF points in number and arrangement. Single point center is not a good choice as it is hard enough to keep a moving subject in the frame let alone keeping the center AF point on the subject. On the other hand, using the largest point matrix might lead to the camera incorrectly focusing on back ground features. A 6x6 0r 12x12 AF matrix is a good place to start. The target size relative to the frame, the background, and your personal preferences will all factor into your final choice. Change and adapt to the circumstances as needed.