I lost a chicken for the first time today. Scooter was a 4-month old black Cochin, very sweet and tame. Most evenings I brought her in from the coop to cuddle with me when I watched TV. She had sour crop but I think I realized it too late to save her, even though I did massage her crop and give her yogurt and oil. I have no idea how it happened; our rooster and the other 10 hens appear to be fine.