Get yourself sorted with a cagey mail center. Scrub the framework of the birdcage with a bleach solution. Then clip off the wires from the front and back, leaving a few to create mail slots.
To make shelves, cut dowel rods slightly longer than the cage width and notch the wood to help it grab the wires. Cut glass or plexiglass shelves to fit, and place them on the dowel rods.
See another cool mail storage solution.
Next: Make Metal Newspaper Racks