Behaviour disorders

Possible causes for feather pecking:

nutrition deficiency (especially calcium, sodium, vitamins and essential amino acids)
Mistakes in the feeding-management (pelletised feed reduces feeding time by a fast feed intake. This can lead to boredom).
poor husbandry management (crowded barns, deficient exercise and winter garden space or even the missing of cocks)
genetic endowments (feather pecking is in part congenital)