The feathering of the head of a bird can be an indication for behavioral issues. Poor feathering can be caused by mechanical damage for instance by the feeder system, but it can also be a sign of competition for dominancy. Birds have a very strict dominacy ranking in nature, and until a group size of 100 to even 150 birds the individiuals in a group know eachother and have a stable pecking order, after initial fighting to establish that ranking.
In bigger groups as we use in our commercial production systems, the ranking is much less stable and especially with higher densities there will be more competition for that dominancy. The fighting for dominancy is typically done by two birds (especially males) that are standing high up opposite of eachother with the neck feathers set up and trying to intimidate eachother.
However, birds confirm their dominancy over less dominant birds by pecking the other on the head. Especially when the density is high and the birds have a continous struggle to maintain their pecking order, a lot of head pecking takes place and as a result more birds that are less dominant will have feather damage on the heads, even sometimes resulting in pecking wounds.
This problem is typically seen in male populations during rearing, especially at increased density. In floor feeding systems we usually see it more than in chain or pan feeding systems, as the birds are not lined up during eating and will "meet" eachother more.
An increased level of damaged feathers on the head in rearing can indicate later problems with dominancy and mating behavior, as a male that will not be dominant during rearing will have less chance to become a dominant male during production. Reducing the density and light intensity and giving the birds scratch feed in the afternoon might help to reduce the problem.