[4] The island was chosen as a unique and protected place to provide a public window for rare New Zealand native birds on the edge of a large city and it also lacked introduced predators such as mustelids which were present on the mainland.

At that time, although the island was devoid of suitable habitat and food sources, the hope was that native forest would regenerate naturally.

It became apparent that natural afforestation was happening very slowly because a forest can only grow at its margins, and the island was covered mostly with dense grass and bracken fern.

A plan was formulated to establish a nursery to collect cuttings and seed in order to expand the small pockets of forest habitat that were left in some of the valleys.

The kiore were killed by an aerial drop of poisoned bait, which was controversial due to its lack of planning and the effect on other wildlife.

[9] These are red-crowned parakeet (kākāriki, Cyanoramphus novaezelandiae), North Island saddleback (tīeke, Philesturnus rufusater), brown teal (pāteke, Anas chlorotis), whitehead (pōpokotea, Mohoua albicilla), takahē (Porphyrio hochstetteri), little spotted kiwi (Apteryx owenii), stitchbird (hihi, Notiomystis cincta), North Island kōkako (Callaeas wilsoni), fernbird (mātātā, Poodytes punctatus), North Island tomtit (miromiro, Petroica macrocephala toitoi), and rifleman (titipounamu, Acanthisitta chloris).

The closest land on the tip of the Whangaparāoa Peninsula, Shakespear Regional Park has recently (2011) also become a mammalian pest-free fenced sanctuary, increasing immigration of the birds on Tiritiri to the nearby mainland.

It is a popular destination for daytrippers, with trips often fully booked,[2] attracting some 30,000 visitors annually, who enjoy an intensity of birdsong rarely heard on the mainland.