Setting for 90D and 100-400mm II for birds in flight

[AdoNetok]

I just learn to use Canon 90D and Canon 100-400mm II for birds in flight.
I set up C2 for this project.
I try to take photos for Forster's tern at the bay where most time is sunny.
Here is my setting.

Camera: AI Servo, ISO: Auto, Drive: Fast shooting, 1/2500, 7.1, 9 points focus,

Lens: FULL, AF, STABILIZER: ON, STABILIZER MODE: 1

C FN II AUTOFOCUS:
1. Tracking Sensitivity... -1
2. Acceleration/deceleration tracking... +1
3. AF Point Auto Switching... +2
4. AI Servo 1st image priority... +1 Focus
5. AI Servo 2nd image priority... 0

There are two things I want to improve:

1) For the first photo, it is hard to catch (focus) the flight bird,
2) Focus is still not perfect.

Please help me.

[Waddizzle]

The first photo is probably hard to capture because of your Image Priority settings.  With 1st Image Priority set to [Focus] the camera will not fire the shutter until it gets a focus lock.  You want to get. The first shoot fired off as quickly as possible.  

Try setting 2nd Image Priority to [Focus].  This may slow down your frame rate, but your images will always have a focus lock, hopefully on your desired subject.  I do not see any point in firing off continuous shots and many of them are OOF.