I went ahead and shoved in more shavings, maybe raising the level by a couple of inches. Still nonstop pecking. So I added another couple of inches. Pecking stopped! Flicker then sat in the hole looking out for much of the day. Now about ten days later she may be sitting on eggs. Fingers crossed. So the advice to fill the nest box fully up (with sawdust), as compared to the advice to only put in 4 inches (of wood shavings) seemed to work better in my situation.

Wow-I've certainly not seen it

Wonderful -- thank you for sharing! I would have been as thrilled as you to see them.

Your pictures are great! I've had only one Northern Flicker and that was about 3 months ago and I've got 3 suet feeders! Lucky you!