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Those holes are almost certainly made by a woodpecker. That probably isn't the real problem though. That wood is almost guaranteed to be infested with insects.
I rebooted a woodpecker once. One started drilling a hole on my shed. There were no insects, sometimes they just obsess on something in the wood like a knot or a nail hole and just start drilling. This woodpecker kept coming back making the hole bigger and bigger. So I took a small target and stapled it to the board with the bullseye right where the hole was. The woodpecker landed and stared at it. Cocked it's head to the left and then cocked it to the right a couple times and flew away. I removed the target but he never returned.
Cocked its* head
It is head