Recently I noticed a couple of fairly large holes drilled in a cottonwood out front. The picture here is of the largest of these. The hole is about 1 1/2" deep and located about 5' above the ground.
Obviously this is a very different kind of hole than the all-over bark thinning that the downies are doing on the bur oak.
The only woodpecker I've seen in this tree is a hairy woodpecker, so presumably he did the work. I can only hypothesize that he was after cottonwood borer larvae, or some other insect, as the limb is way too small to support any kind of nesting hole. I'm open for suggestions, though.