I have not observed any evidence either way, (so far as i know, my girls are well-brought-up and perfectly behaved young ladies, but then, I don't spend the night with them in the coop, even when the pophole's open) but found this elsewhere and thought perhaps some of you might have further observations to add, in the interests of scientific research.
http://www.fartingchickens.com/dochicksfart.htm
http://www.fartingchickens.com/dochicksfart.htm