So the last few years we learned how to keep the eggs coming without any supplemental heat or light in our open air coop.
We noticed a few rules - and one of them is that the hens that molt or take a break due to winter will generally come back into lay very soon after the Winter Solstice.
It was surprising to me that the hens would notice the lengthening of days so soon, but every year they have come back into lay within about 1 week following the Winter Solstice. Not all, of course, but one, then another, then another, etc. No matter how cold, no matter how wet or wintry, eggs start to appear again that soon.
Not this year. The pattern was broken in a surprising way.
About a week BEFORE the Winter Solstice, one hen started to lay. Two days later, another, then a third.
We only have ten hens left after thinning the flock this fall, and we had only two new hens this year, but they were last winter's hens, not spring hens. We did not have a heavy molt in the hens, but we were without eggs for about seven weeks. I actually had to buy eggs. And I really noticed the difference in my ability to digest ours, as compared to commercial eggs (even getting the expensive ones).
We changed exactly three things this winter:
1. Fewer hens in the coop. Just two guineas, and ten hens.
2. No more layer feed. Lots of scrap, a rotation of various grain types, and several protein sources (including butchering scraps from everything but poultry). We also supplement with oyster shell when we don't have enough eggshells to toss in.
3. Mealworms were added to their diet whenever we did not have other sources of meat proteins. Just a handful once a day.
So we are not certain what it is that made the difference, but it is a good difference. Whatever we did, we did it right.