The ventilation system includes {HEAD ~ a stub venting tube} that together with {TAIL ~ a throughbore} in the lower floor allow the modularly stackable centrally ventilated bird houses to be stacked, four lower compartments, four lower dowels, four upper compartments, four upper dowels, and a vent cap 
The ventilation system includes { HEAD ~ a stub venting tube } that together with { TAIL ~ a throughbore } in the lower floor allow the modularly stackable centrally ventilated bird houses to be stacked , four lower compartments , four lower dowels , four upper compartments , four upper dowels , and a vent cap
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH