There may come a time when your chicken appears to be going bald, but worry not as molting is a natural part of a chicken's life. Hens and roosters alike both molt, which basically translates to shedding out old, dull feathers and replacing them with vibrant, new ones. Molting generally begins at the head/neck and progresses down the back/over the wings and onto the tail.
Chicken molting takes place when the day becomes shorter than the night, usually in late summer/early fall. Daylight hours regulate egg laying, so as the days shorten, signifying the coming of winter, egg laying halts to allow growth of new feathers to help keep them warm in the winter. Molting can also take place after their eggs have hatched in the case of broody hens as they return to a normal feeding routine post time spent on the nest. Stress can also be another factor that leads to molting.
Chicks will molt at least twice in their young lives before their first annual molt. Initially they will molt beginning approximately one week of age, completing that molt at approximately four weeks of age. The chicks' down will at that time begin being replaced by their first feathers. When chicks reach an age of 7-12 weeks old, another molt will take place and a second set of feathers will replace the first. It is around this time that a rooster's cone will become visible. All adult chickens will molt annually, beginning as they reach a year and a half or so in age.
You may notice the difference in types of molt, be it hard or soft. In a hard molt, your chickens will lose the bulk of their feathers all at once before slowly growing new ones. Hard molts result in a lot of exposed skin that can look rather harsh and can be easily pecked through by other chickens, so be vigilant about monitoring this. In a soft molt, new growth comes in and gradually pushes out the old growth, creating a more uniform appearance.
Growing new feathers is quite physically demanding so it is important to up your chickens' protein intake during molting. Supplementing their regular diet with meal worms, tuna fish, or black oil sunflower seeds area few ways to do this. You can also add commercially available chicken feed with 20% protein or higher. Remember that chickens will stop laying eggs during molting regardless of food availability but this should not be a reason for you to neglect their needs. After all, feathers are 85% protein and eggs are around 13% protein so even the most efficient chicken cannot grow feathers and lay eggs simultaneously. In fact, their fertility/virility actually decreases during molting to help them through the process.
When your birds are molting, it is important to do everything in your power to make and keep them happy and healthy. This is necessary for their immune system and will ultimately affect yours as you consume their eggs and/or meat, so be sure to nourish your chickens and they will in turn nourish you.