What is a bird nesting ball and what makes alpaca fiber so special as a nesting material? Each  ball is hand-filled with alpaca fiber. Hang the nesting ball in a tree which blends into the environment. Alpaca is a hollow fiber which wicks water and when wet, quickly dries to its natural fluffy state. The delicate fiber, unlike some nesting materials, is easily used by birds and does not attract predators to the nest. The birds will love you for it!