Birds are known to occasionally eat wood ash and charcoal, materials that are rich in potassium and calcium. The Black Honeyeater, recently observed locally over summer, is renowned for eating charcoal and ash. After a little research I turned up a paper from 1965 (M. Baldwin, Emu 64 (3) p.208) where the observer noted a number of species consuming charcoal; including Fairy Martin, Dusky Woodswallow, Banded Finch and Zebra Finch.
Until yesterday I had never witnessed this behaviour from an Eastern Rosella. The bird pictured below was feeding with its mate on the ground around the remnants of an old fire when it picked up a small piece of charcoal and proceeded to nibble gently as I watched on from nearby.