Preening our rooster Sven, and fun feather facts. 🪶🐓 When birds grow new feathers (called pin feathers), they come out covered in a protective, thick, waxy casing. This is because new feathers actually have a blood supply running through the main shaft! The casing protects them while the blood supply is there. As the feather matures, the blood supply recedes and then the sheath dries out and begins to break down. If a blood feather breaks before the supply recedes, it bleeds profusely. Birds w