Preening is a very important grooming activity for birds, they do it every day. They arrange feathers by drawing each one through their bill, they lubricate them with a fatty substance secreted by the preening gland (just above the base of the tail), and they remove any soft sheaths from pin feathers. Any feathers they can't reach with their beak they will scratch with their toes. Finsters will also preen each other, especially in spots they can't reach themselves by beak. This is called allo-preening, and is usually done by mated pairs. This is an important bonding behaviour. These photos were taken awhile ago by Fizzy. I think that this is the late Chocolate preening her offspring Bosco, but I don't know who the tea bird is.