The chicken chick just has a blog post about this, with consultation from a actual avian vet.
http://www.the-chicken-chick.com/2011/09/supplemental-light-in-coop-why-how.html
That led to another link with very interesting info- fluorescent lights are not good for chickens.
http://mikethechickenvet.wordpress.com/2012/03/30/chicken-vision/
There I read:
"Fluorescent lights flicker on and off at a rate above what we can see….you notice it on old fluorescent tubes that are dying….the flicker rate slows down and we can see it. It is exceptionally annoying. Birds can see the flicker in many fluorescent lights, especially dimmable ones that are at lower intensity. It would be like being in a dance club with strobe lights on…..all the time….it drives them nuts…literally"