Another issue with artificial daylight hours in winter is that hens who are pushed to lay at high rates all winter have been shown to develop reproductive cancer. I provided a little artificial light at both ends of the day during my first winter of having chickens. This winter, I am choosing to have a heatlamp hanging over the large galvanized waterer come on around 5 or 6 a.m. to melt any ice that may have formed in the tray. I will not add extra at night. Heatlamps, as a rule, do not give off bright light anyway, so I am not really adding artificial light, per se.