Baked eggshells - do you feed them?

Fantastic source of calcium for finches and they love them.

I save them up next to the stove and then every so often I put them in the oven. Just spread them out on an oven tray and put them in just after you've finished cooking dinner. Turn the oven off and let the residual heat cook them. And that way it doesn't matter if you forget about them - they'll be cooled and ready to feed out in the morning.