This could be one of several things. Firstly, chickens will molt at about 18 months of age, and this is when they lose their feathers. If your chickens are this age, then this is normal and you don't need to worry.
They cold also be losing feathers because of mites. Check around the bald spots for brown or white bugs, and possibly eggs, which will be on the feathers around the area, making the feathers look really dirty.
They could also be picking each other. This is a bad habit chickens pick up when bored. They will usually pick in the same area, and you will need to stop it or soon they will all have no feathers at all. Observe them, and if you think this is it, you will need to buy an OTC No Pick which leaves a bad taste and discourages this behavior.
If you have a rooster, this could also be caused by him when he mounts a chicken to impregnate her. This is also nothing to worry about, although I would trim the rooster's claws to prevent damaging the hen's skin.
They cold also be losing feathers because of mites. Check around the bald spots for brown or white bugs, and possibly eggs, which will be on the feathers around the area, making the feathers look really dirty.
They could also be picking each other. This is a bad habit chickens pick up when bored. They will usually pick in the same area, and you will need to stop it or soon they will all have no feathers at all. Observe them, and if you think this is it, you will need to buy an OTC No Pick which leaves a bad taste and discourages this behavior.
If you have a rooster, this could also be caused by him when he mounts a chicken to impregnate her. This is also nothing to worry about, although I would trim the rooster's claws to prevent damaging the hen's skin.
