I made this image last week just prior to leaving town for a meeting. I had just completed calibrating my 100-400 and wanted to check it out really fast to see how it worked. I am happy with the result!
This is 25% of the original image; hand held with the 100-400 @ 400. Evaluative metering at ISO 800 and f 5.6 and 1/2500 EV - 1/3 with the 1D4.
I like the pose, perch and head angle. I wish the bright spots behind the bird were not there and the whites have a slight magenta cast. I might crop a bit off top and bottom.
You could crop it a little tighter. Whites do not look natural for some reason. Bird is perched nicely, with beautiful catchlight in the eye(With chickadees, it is difficult to show the eye from the black cap, but you have done an excellent job). Excellent head position.