I made this picture this morning.
The little blue tit was looking for some small insects. I like the small water srops at the beak.
Mark III Canon 100 - 400
f 6.3 / 1/640 sec. / ISO 800
Rosl, A very nice image of the Blue Tit. While the focus is spot on the eye, which has the catchlight, the rear of the bird is OOF, not unusual creating images of small birds. Just wondered, if you had another image where the bird was more parallel to the image plane or if you tried with a smaller aperture.
The other aspect is of the space on the right. As the bird is looking downwards, have you tried cropping some of the space from the right of the frame?
I like the composition, pose and BG. Exposure looks good, too. I might have stopped down to f/8 or so for a bit wider DOF but I don't think the entire bird needs to be in focus. Have you experimented with fill flash when you had to deal with side light?