The cockatoo feeds primarily on seeds of proteaceous plants such as "Banksia", "Hakea" and "Grevillea", and secondarily on seeds from myrtaceous plants such as "Eucalyptus" and "Corymbia". Over fifty native plant species are commonly used for food, either as seed or flowers, and this includes western sheoak "(Allocasuarina fraseriana"), orange wattle ("Acacia saligna"), and balga ("Xanthorrhoea preissii"). Typically, Carnaby's black cockatoos sit in the crowns of trees cracking the seed pods or cones. First, a bird chews through the stem holding the item before holding it with its foot and tearing bits off and extracting the seed. Birds may move along the branches breaking stems at random as well. Occasionally they forage for fallen seed and fruit on the ground. This cockatoo acts as an agent in biological control, eating the larvae of invertebrates such as wood-boring insects and moths from rare plants.