Natural wood for perch.

You can learn more about it here https://alenaxp.com/safe-wood-for-perches-and-toys-budgies-happy-life/
Safe natural wood for budgies are Safe wood for Budgies includes birch, beech, oak, hazelnut, ash, maple, elm, and softwoods which include willow, chestnut, apple, linden, and other fruits such as figs, olives, and magnolias.