^Pretty well says it all. Especially for bird photography (but not only that), you aim to focus on the bird's eye.
You set a reasonable
f-stop for the
lens you're using to allow for a fairly useful
DOF (
depth of field). That will
not be the same for different focal lengths, so say f/8 on a 50mm
lens will give you more
DOF than f/8 on a
lens of 300mm, etc... ("etc" means read, study, practise...)
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PS: by way of a "trick", you can (generally) retain the focus setting by lightly but not fully pressing the
shutter button.
This will allow you to recompose the shot as desired.
To reiterate, find the AF pattern that gives you a single, central focus point.