Mt Bruce is also an insurance policy in case the small populations in the wild are wiped out. Some birds are easily disturbed. For example the Campbell Island teal, the world's rarest duck, is nocturnal so it is essential it remain undisturbed during the day so it can sleep. These birds are unique to New Zealand. Many species date from the time New Zealand was joined to Gondwanaland and have been preserved by geographical isolation.
Birds also contribute to the balance of our ecosystem.
Without birds like the kereru, seeds would not be dispersed throughout the forest. All the effects of biodiversity and the ecosystem are not known so plants and birds we think are unimportant today could be extremely important in the future.