http://www.alloutdoor.com/2017/03/01...chicken-flock/McMurray Hatchery has an excellent write-up on ways to reduce stress in your chicken flock. Some of these I have experienced first hand and have seen how stress can contribute to bad behavior.
The list from McMurray:
Water problems.
Inadequate nutrition.
Excessive or Rough Handling.
Fear of dogs or predators.
Overcrowding.
Parasites and disease.
Extremes of Temperature.