I think the complication for many of us (but not for you given the circumstances of your tribes) is guilt.
We see ways in which we believe we failed the chicken from our ignorance or thoughtlessness, or from keeping the chicken in a certain way.
When Posh was taken by a fox I felt terrible because I felt I had failed in my duty of care to her. I had tried to protect her but I missed a tiny spot she managed to get through and it took me a while to get over that.
When Elizabeth died more recently I felt sad for myself because I liked Elizabeth and she was good company. I felt anger at the whole chicken breeding industry to breed an ISA Brown that was so subject to reproductive issues. But I did not feel guilt. She had a good (albeit short) life with me and a rapid and natural death in amongst the members of her tribe.
Although much more recent, her death weighs less on me than does the death of Posh much longer ago.