For the past couple of weeks, we've been finding a dead chicken almost every time we open the coop each morning and we can't figure out what's going on. The birds that have died were vigorous and healthy the day before and then dead in the morning, and we find no marks or wounds on them, nor any lost feathers or signs of struggle. We have had some bitter temps here (below zero nights) but the coop is full of hay and we keep a light on all the time for warmth. Can anyone help us with this mystery? We sure are getting discouraged! We had around 40 chickens in the Fall and now we're down to just 20...... NOTE: This did NOT happen ONCE last winter when we also had below zero weather and snow.