I started out my backyard mini-flock with three hens. Last spring my RIR (not quite three years old) died of abdominal cancer. Yesterday, my 31/2 year old barred rock died of an impacted oviduct (surgery attempted). I'm surprised, I thought my pampered, suburban hens would have much greater longevity. My question for members: in your experience, what is the average age expectation of a backyard chicken?