Use pine fines for bird cage litter
It works great. I used to hate to throw out the good poop that was stuck to newspaper. The soldier flies will compost dirty paper in the compost barrel, but I wanted to use the droppings directly.
The calcined clay & zeolite kitty litters worked fine but were heavy enough to make the plastic trays sag. You need to have a grill over the trays to keep birds from ingesting litter.
Corn cob is ok but expensive & wood shavings got blown out by the birds' flapping.
The pine fines from a huge sack of Lowe's HapiGro landscape mix are perfect--just dense enough to not blow, flaky to catch feathers & poop, clean, dry, pleasant smelling, not too dusty to harm birds. I keep them in a brown bag inside a kitchen-sized garbage can. Shovel up dirtied litter with a dustpan into a bucket & distribute it to roses & other plants.
I initially rinsed, then sun dried them on top of an old screen door, but don't think this is necessary--I see no evidence of mold or other pathogens on the stuff, plus my birds have a grid over the drop pans.