They may find hard enough material suitable for grit in the sand, hard to know.
I like to just buy a bag at the feed store, it's crushed granite and will last a long time. I just put a small amount in a cup inside their housing and they'll pick up a piece or two as needed.
I like to just buy a bag at the feed store, it's crushed granite and will last a long time. I just put a small amount in a cup inside their housing and they'll pick up a piece or two as needed.