Predators can indirectly structure local plant communities by altering the diversity and behaviour of herbivores. These ‘trophic cascades’ can be seriously disrupted by the local extinction of top predators. They can also be restored by the subsequent re-introduction of top predators by conservationists. Here, we investigated trophic cascades involving kākā, puriri moths and their host trees. New Zealand kākā (Nestor meridionalis, Nestoridae) are large parrots that were extirpated from most of its range in the 20th century.