Well I didn't do any scientific research about the project but it definitely works and the bees/hornets like it. We also have a lots of birds (20 or so differen

Well I didn't do any scientific research about the project but it definitely works and the bees/hornets like it. We also have a lots of birds (20 or so different species) and no one attacked it so far. I guess I can try deeper holes on my next iteration :) it will depend on the firewood.