My birds have been acting unusually the past few days. Normally they have been laying around 4 eggs a day the past few weeks. But for the last 4 days there hasn't been a single egg in the coop. Last night when we went to lock them up, almost all the girls and boys were atop the pen and refused to go inside. We had to make quite an effort to get them to go back into their pen and their coop. We've never seen the flock do this before, certainly not the night after a snowstorm. In the warmer months, a few would make a half-hearted effort to spend the night out now and then. But last night the whole flock seemed uneasy about going inside. They seem fine today, but I still don't see any eggs. I also haven't seen any rodent tracks in the snow. I'm puzzled. If something was eating the eggs, I expect I'd see debris, but so far I haven't seen any. Any ideas what's going on?