Hooded Crow eating lichen

(Originally published in SBN)

I watched and photographed a hooded crow eating lichen/bark from a fallen beech tree. I thought at first it was pecking the tree just for the hell of it, as crows do, or perhaps collecting nesting material, but it definitely swallowed the lichen and the photo shows this.

Could the bird have been finding insect food and be swallowing the lichen inadvertently or is it possible that vitamins or minerals could be contained in the lichen?