Finch lost his tail feather

Question
I have 2 Spice Finches and 2 kittens.  Somehow one of the kittens snuck into my room and pushed the cage onto the floor.  One of the finches lost his entire tail feather and cannot fly.  I make sure he has accessible water and food at the bottom of the cage but will he grow it back? I don't want him to get sick being at the bottom of the cage where the other bird leaves his droppings.

Answer
This sounds a lot like stress. The feathers should grow back in time. Move the little guy to separate, smaller cage. The feathers will grow back in time just make sure he gets heat (a heat lamp from the reptile section of the pet store works) and keep it around 30C. This will help relax him and keep his immune system up until the stress is gone