Here's some information I found on another site about molting:
Molting is the shedding and renewal of feathers and occurs about once a year. The order in which the different sections of the bird lose their feathers is fairly defined: head, neck, body, wings and tail. Molting is a difficult time for birds, since it involves hormonal fluctuations and increased energy requirements. Eliminate stress during this time: keep temperature in a narrow range (70-80o F), provide a high quality diet, and each day mist the birds with a fine spray or provide a pan for bathing. It takes about seven weeks for new feathers to complete their growth cycle. Domesticated chickens bred for high egg production have a definite molting pattern. A natural molt does not normally occur until the end of an extended, intensive laying period. Chickens that have been laying heavily for one year or longer molt easily in the fall since this is the natural molting season. If they finish their intensive year in the spring, they do not molt easily and may wait until the fall. A chicken loses feathers from various sections of its body in a definite pattern. The order is: head; neck; feather tracks of the breast, thighs and back; wing and tail feathers. Some birds molt more slowly than others; some molt earlier. A good high producing flock tends to molt late and rapidly. Decreasing day-length is the normal trigger for molting. Therefore, lighting programs for egg production flocks should provide either constant or increasing day-length. Stresses caused by temporary feed or water shortage, disease, cold temperatures, or sudden changes in the lighting program can cause a partial or premature molt.
*Did you know that when you have questions about your chickens you can go to this great forum and people will start posting replies almost immediately? I have used it for many reasons asking things like, "What breed do you think this pullet is?" to "Can chickens get fleas?" It's been a great resource. You should check it out!