The term 'bird bills' refers to the BEAKS and nebs of birds. Nebs are the fleshy, often brightly colored appendages that protrude from the upper mandible of a bird's beak. BEAKS are the hard, pointed structures at the end of a bird's bill that are used for feeding, grooming, and other activities. Both nebs and BEAKS are important for a bird's survival, as they help them to find food, defend themselves, and communicate with other birds.