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Keep at it Dick. On the 7D II there is a setting in the menu to limit your auto ISO range. You might set it 100 - 1600. Then you can go into M (manual) mode, set your aperture and shutter speed and leave ISO in auto (A). On my 500mm, f/5.6 seems to be the sharpest and f/8 when I use the 1.4x. Though f/6.3 was not bad at all even with the 1.4x on.
Note you can even use EV comp. in M (manual) mode on the 7D II. You trick it by first going into S (shutter priority mode) and setting your EV; for example +1. Then switch back to M mode with ISO in auto and the EV is low-and-behold +1. Nice back door for a feature that is only on 1Dx.
Now if there was a hack to get spot metering on the 7D II. Possibly in a firmware update?
Anyway...also remember to set the AF drive to Servo for the birds as they move around. Even slight position change can cause a focus miss. Second, check your lens settings. If you are on a tripod, set IS to mode 2. If you are really close to the bird (seems since you filled the frame with that little guy) you should check that the distance limiter is set correctly to Full.
You might have all this dead on, just thought I would throw those tis bits out there.