set AF to C-AF rather than C-AF+Tracking as the tracking mode is not as reliable
set AF+MF to OFF as this is generally not needed and having it on risks accidentally changing focus
set AFL/AEL to C4 and set Half-Way AF to inoperative (E-M1III only) to allow assigning this to the Lens button instead of the shutter release
set AF Scanner to Mode 3
set AF sensitivity to +2
set C-AF Center Start to ON for All Area mode but probably not useful for smaller region modes
set C-AF Center Priority to OFF (E-M1III only) as you will have more chance of AF locking on background if bird is not in the centre of your AF region
set the AF limiter in the camera to a distance range which excludes the foreground and the background so the camera will use all its computing power just on the subject region and it will no longer AF on the background!
set the AF sensitivity to loose (+2) when there is no distracting background (eg. shooting against the sky or with the AF Focus Limiter excluding the background, and the bird is flying across the scene.
set the AF sensitivity to tight (-2) when there is a distracting background you can't exclude with the focus range limiter such as birds in a tree with lots of branches.
otherwise you can leave the AF sensitivity to default (0)
set drive mode to LOW mechanical shutter 10fps - seems to give best results although many use LOW 10-18fps electronic shutter instead or Pro-Capture mode (DO NOT USE a High burst mode as you lose C-AF!)
set AF region to all AF points if there is no distracting foreground or background (or these have been excluded by the AF range limiter
if the bird is not moving much, you may consider using only 1 AF point so you can place it on the bird's eye for critical focus.
otherwise set AF region to group of 25 points - this is probably the best option for obtaining the highest number of keeper shots (perhaps 10-15% better than the all points mode)