It seems like out of the blue one of my hens was making a lot of noise is a rhythmic manner. It was hard to tell if it was loud breathing or a vocalization. Four hours later it seems to be related to breathing.
My research here suggests impacted crop-- but in fact her crop was pretty empty and she has eaten heartily. Another possibility is gape worm--its well below freezing with snow. Also,she is not exhibiting the usual behaviors.
So, I conclude it is respiratory and have brought her inside. Partly because if she is really sick she doesn't need to use her strength keeping warm and second in case she is contagious. I am giving her an antibiotic in her water although I really don't want to do that. Less seems to be more with chickens sometimes.
Any opinions or input welcomed.