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Find a dairy farm. They'll be glad to have you.
On the trap that you had. Was the entrance centered on the roof? I think the advantage of the inverted roofline is that you can run a couple of roost poles up high in the trap. This would allow for more birds in the space available, make the caught birds decoy to the trap door and caught birds would not have a line of flight to the doors because they'll roost above the trap entrance.