I got up this morning thinking that I'd have to have a serious discussion with my White Dorking. She hasn't laid an egg for a couple of months. She went through her first molt in November. She took it rather hard, even lost her dominant place in the pecking order.
Chickens are said to require 14-16 hours of daylight in order to lay eggs, but my observation is that lengthening days, even if shorter than that, brings on laying.
Sure enough, just as I was losing patience with her, she laid a beautiful large tinted egg!
Her Buttercup companion hasn't laid for a while, either. She molted a couple weeks later than the Dorking, also taking it hard. The two brown egg layers, a Partridge Rock and a Speckled Sussex, have laid through the declining days thus far. The Buff Orpington, new to the flock a couple of weeks ago, lays regularly, three or four eggs a week. I expect that will pick up as the days get longer, but I'm impressed that she's hanging in there.