Well, Thing One gave up. Her eggs were due to hatch on the 11th; she deserted the nest on the 13th, and went back to her regular roost. We candled the eggs (she had about 12) and they were not all hers. There were no embryos in any of them. She was not in a traditional nest box but an old bicycle cart that they all adore for setting. It is surrounded on most sides, has straw, and is in the barn so it is sheltered. We have had two other hens use this for setting; one was successful, the other would've been, but a raccoon got her and her eggs and mostly developed chicks inside a few days before they were to hatch. (We have corrected that problem)...Both of the other hens were also setting during the colder weather. So what happened? Thing One was very faithful on the nest. Is this a fertility glitch in our roosters? Or was it just too cold? We were very dissapointed because we had Christmas chicks last year and we were very much looking forward to these, after Uno's death, especially.