Howard5252 wrote:
If the entire bird fits inside of one of the focusing squares, don't expect too much when you blow the image up. The old adage "GET CLOSER" applies here. When you can, getting closer will always improve the sharpness of your photo.
The other bit of advice "Focus on the eye" ... Very hard to do if you can't see the eye. You were way too far to expect anything good. Keep at it, you will learn when the bird is just too far.
I agree 300 feet with a 400 is mission impossible.
You must get closer turn ISO up you were too low to get proper shutter speed.
Try again when the sun is shining you will find it works much better.
You can not get great focus when you can not see any details. YOU MUST BE CLOSER