Is anyone showing signs of them on your trees? I saw a few oaks on my place that looks like they got hit with buckshot. I couldn't see any entry past the bark but if it's them I'm they got in.
In my experience carpenter ants will eat through dead/inner layers of oaks. Specifically live oak trees. Personal example, I have a 250+ yo live oak. When pruning this past winter, saw the inner layers eaten through by carpenter ants. The tree is healthy. Hopefully this info is helpful.
If the holes aren't through the cambium and in somewhat linear pattern it's probably sapsuckers. They quite often hit trees on lower trunk-typically younger trees.