When a chicken is about a year old she will start to lose her feathers. Don't panic - this is molting, and it happens every year. Molting is a completely harmless process of plumage rejuvenation, and all birds undergo it.
Molting usually occurs in the summer, although a flock does not always molt in unison. They will stop laying for the duration of the molt, and will look messy and balding while the new feathers grow. They may also be more short-tempered than usual.
Molting is an annual process, a messy but natural way of keeping feathers in great shape
You don't need to do anything during the molt other than making sure the birds are well fed so that the new feathers grow healthily.
If a hen loses feathers and develops bald patches that linger, with no other sign of a molt, there may be parasites or illness at work. Watch out for unusual behaviour – listlessness or a hunched posture, for example – and if in any doubt about the bird’s health, speak with your vet.
Picking
Chickens with bald patches outside the molting season may well be victims of "picking". This is when stressed or angry hens peck at each other, and is nearly always the result of poor environment. Hens need lots of space, and if there’s not enough of it they will take out their frustrations by plucking their neighbors' feathers.
Miné, 5 September 2021
Hi, is the any way of telling the difference between moulting and pecking? One of my bantams has lost almost all of her tail feathers and seems to be moulting but i cant tell which is going on…she isn’t keen to join the rest of the flock and has been keeping a distance, not eating much either. I haven’t seen any pecking behaviour but a worried I may have just missed it. We separated her but i just read that this isn’t advisable if they’re moulting as it can cause stress…? Any tips would be much appreciated. I will up their protein and vitamins now