19 gauge is very then & while it will hold the birds just fine it is easily damage by you handling it. I'd suggest 1/2x1 for the bottom & 1x1 for the top & sides unless you are concerned about predators that you need the smaller wires on the sides also. This is also assuming your talking about Coturnix.
I've used the 1/4" hardware cloth but it is more work to clean on top of not as sturdy. Bitties need something in the bottom not to fall through tho.