I've been experimenting with birds and birds in flight for awhile, both with my K-3 and K-1. It's definitely a practice makes perfect process. For birds not in flight, I will sometimes use a tripod with a gimbal attachment. For the most part for birding (hand held or tripod mounted), I use TAV with minimum shutter speed from 1/750 to 1/1000, and higher if light allows; aperture is set to the lens's sweet spot (F8 for my D-FA 150-450, or F13 when I use my F-300), and I let the ISO ride (the dynamic range on the K-1 is significantly better than the K-3, so I don't get a lot of noise if the light isn't great). I use center weighted average metering, AFC with Auto- 9 focus points, and continuous shooting high drive mode in 4 to 5 image bursts (the K-3 has a better frame rate than the K-1, so I can use a longer burst if needed). I also shut off every in camera adjustment and shoot in raw only in order to keep the AF fast. Lastly I use back button focus.
There's a great article that for shooting sports that translates very well to shooting wildlife.
Guide to Camera and Autofocus Settings for Shooting Sports - Articles and Tips | PentaxForums.com
Attached image was shot handheld at 1/3200, F8, ISO 800, focal length 450mm.
---------- Post added 10-18-18 at 09:29 PM ----------
Originally posted by tuggie76 K3ii, 300mm lens with 1.4 convertor
One other thought. Besides for the camera settings, depth of field is one other thing you need to think about. The longer the lens, the shorter the available depth of field. Add a teleconverter and the available depth of field gets reduced. For example, a 300mm lens on a K-3 at F16 and 10 feet from your subject will give you a depth of field of approximately 2-3/8" but add a 1.4x teleconverter and that DOF at F16 becomes 1-1/2". Go to F8, that DOF gets even more reduced. So it becomes trickier to get any or all of the bird in sharp focus.
When I first started chasing birds, I didn't really understand the relationship of lens length, distance to subject and how much DOF was or wasn't available. Often I'd get a soft bird and a really sharp branch because I was often pre focusing on a branch an not on the bird. Fortunately someone on the Forums explained this issue to me and I used the PhotoPills DOF calculator (they list Pentax bodies under camera types) to help me understand the relationship of all the factors. It was a bit of an eye opening lesson. It really helped me dial in my camera settings for my lens length and what my limitations where going to be.
One other interesting item of note - a full frame sensor will have a greater DOF than a crop sensor. In the above example, trading out the K-3 for the K-1 (and everything else being equal) the DOF increases from 2-3/8" to 3-1/2", and with the 1.4x TC the 1-1/2" increases to just over 2-3/8".