Ash baths ....is this true?

I read a book recently and they put their potato peeling on the fire, might try that, usually just bin them 

Well I guess the bottom line is that the birds sem to enjoy it and if helps to keep some of the itchy critters down then I guess its worth doing

Oooh, i love old superstitions, i wonder why she thought that?

Well, according to "Keeping Poultry & Rabbits on Scraps" (Claude Goodchild & Alan Thompson 1941 - reprinted 2008)
"An indispensable piece of equipment is a dust bath. This is nature's remedy for getting rid of insects. ... Is large box of dry earth, ashes or sand sprinkled with flowers of sulphur.  ....placed in corner of scratching area to prevent dust with lip nailed on all round to prevent dust from being scattered."
The fact that this was during WWII presumably the ashes were taken from household fireplace. The fact that they state 'flowers of sulphur' presumably this nowadays could be substituted with 'Barrier Red Mite Powder' or similar.