RE: henned up toms
Also I think the weather and temp will push things somewhat, one way or the other but the theory that it is photoperidism (exact word?) makes the most sense. That is the length of daylight will trigger it. It's the only consistent thing from year to year. I guess if it's really cold a hen may not wish to breed because of temp effects on nesting factors but utlimately it is the length of day that starts things in motion.