If a chicken is shivering it needs some sort of protection. If you can find the same kind of material used to make horse sheets (ripstop nylon) you can make a coat for chickens and it won't hurt growing feathers. The quilted kind is even better. This stuff ain't cheap but you can buy it on Amazon.com. You can also recycle an old fleece jacket to make a few coats for your chicken. If you can't make a coat for your shivering chicken bring her inside. Plastic animal carriers are great for temporary homes and are perfect for this situation. Not uncommon in my house to find a recovering critter in one of my bathrooms.