Went out to check the nestboxes this morning and one of our year-old RIR's was dead in the box. We gave her a thorough checking over and found a larger than normal egg just breaching the vent with some swelling and hemorrhaging around it. It appeared she was eggbound. We found no evidence of mites, lice or other vermin. This same chicken appeared alert and playful earlier that morning, begging for a scratching and petting session, and has been one of our most consistent layers. We are not adding lighting or doing anything to promote laying in the winter to give those chickens that need to rest the chance to do so. Even so, this girl still was laying 3-4 eggs per week. This is our first winter with chickens, and it has been very mild here in southern Ohio, so maybe the hens are laying more than they would in a normal winter. Any thoughts? We want to learn from this as much as possible. Maybe we have been lucky but this is our first loss a year into raising chickens.