I built this bird cage for about $10. It slides into the open cage door of the other cage.
Step 1: Materials
2 Wine boxes (the same size or one can be slightly longer. You will use these for the top and bottom) ~Free-$2
2 Cheese Log boxes (can acquire them from whole foods or anyplace selling higher end cheese, arriving early in the morning when they do production or calling the day before for holding. Goat cheese logs or small brie rounds come in "slatted boxes" you will use the slats for the door area) ~ Free
1 Roll of 1/2" hardware cloth (Do not get copper, zinc, or brass it is toxic for the birdies) ~$8
Branch (To block sharp wires at connection point)
Step 2: The Cage
2.Pull the ends together so it makes a loose roll and work the bottom edge into the bottom of the (the smaller one if there is a smaller one) wine box. Trim if you need to and work the wire into the edges of the wine box, so it all fits nicely.
3.Use needle-nose pliers to bend wires in to connect.
4.Staple the wire so it is secured to the wine box.
5.Place the branch (Finding a branch with little branches off of it can create a perch for the birds) against the connected section as to block the sharp wires. You can attach with rope, string, zip ties, etc. stay away from glue, anything painted, wire made of copper/brass/zinc.