My experience is that they are not required to remove their head coverings. I cruised with a friend who boarded with a head covering due to chemo hair loss. She was told she had to remove her head covering for the photo and if she wore her wig ashore, she would have to remove it upon reboarding. Her husband talked to the head of security and asked specifically about head coverings for religious reasons. My friend was a very private person and while everyone in the large group sailing together knew that she had lost her hair, none of us had seen her without her wig or head covering. It was very painful for her.