I have tried the traps around my friends farm. They didn't seem to work because they have lots of food everywhere. Climb up the silo just after dark with a fishing net. It also helps if the silo is mostly full of silage. Get a friend to go up on the inside of the silo after you get to the top and be ready. It's a bit spooky the first time you do this because the birds fly right into you. (Be ready and be careful!)
Things to bring:
Flashlight for the person going up on the inside of the silo.
Fishing net, a big one.
Old pillow case to put the birds in for transport down.
Rope to lower the pillow case and fishing net down.
This has worked the best for me. The traps were bated and left at the farm for two weeks without cathcing anything but a rat. The first time up the silo I got sixteen birds. One other thing, only do this every few months because the birds figure it out if you are up there every weekend. Good luck!