The ventilation system includes {HEAD ~ a stub venting tube} that together with a throughbore in the lower floor allow {TAIL ~ 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 
allow
The ventilation system includes { HEAD ~ a stub venting tube } that together with a throughbore in the lower floor allow { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL 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