Although, in general, small birds were unable to enter the cage, on occasion they did get under the net if it was not sealed at ground level. If desired, minor modifications could be made to keep birds in or out. The materials needed to construct the cage are listed below. Larger enclosures can easily be constructed by adding more supports. PVC is sturdy but heavy.
Rope is lighter and less expensive.
When bent into position, these will form the framework for a cage about 3 m high at the center. These stakes are needed to hold the cross-supports in place. Drive the stakes into the ground in 2 rows 10 m apart. If needed the end cap can be placed over the end of the pipe to prevent flaring of the pipe as it is driven into the ground. The exact height of the EMT stakes above ground is unimportant, but leave no more than one-half of the EMT protruding.