There are quite a few woodpeckers around (I heard one going at it yesterday), but I did a little research and think that it is likely carpenter bees. The woodpeckers wouldn't have anything to support themselves on where the holes are. In addition there is sticky stuff coming out of the holes which I suppose could be some sort of wax or honey discharge.
I saw on the inernet that there is a certain type of powder that you can spray in the holes called Drione and afterwards you fill the holes with cork. There is supposed to be something else that you spray on the wood to keep the bees from coming back. I have seen quite a few bees around there too.
Thanks for your help nonetheless!