Hi Allen. This is very cool behavior that you captured! It looks like the old head "skin" is still attached at the front. Nice lighting, very good exposure on the whites and yellows (which tend to blow out very easily), good overall sharpness- except at the very bottom of the frame where it's starting to go soft (a very minor point for me), and a clean background. As usual, this is very nicely done!
I like the exposure and composition, it is good to see a behavioural image. The image is well focused but not the sharpest I have seen (possibly the combo of sigma and tamron?).
You found a very interesting moment, Allen! Would be interesting to watch the process unfold. Perfect BG for your subject. Top and bottom a little tight for my tastes.