Most of New Zealand’s land birds have become extinct within the last few decades or centuries, or are classified as threatened or endangered. Because most are long-lived and reproduce at a low rate, slowly declining populations may eventually become extinct.
Forty land bird species have become extinct, and the Department of Conservation classifies 37 of the 51 living species as threatened.
Many land birds, including the saddleback or tīeke (Philesturnus rufusater and P. carunculatus) and the stitchbird or hihi (Notiomystis cincta), became extinct on the mainland. They survived only on a few small islands free from mammalian predators.
Some, such as the kākāpō, little spotted kiwi and black robin, are true refugees. They have been deliberately moved to island sanctuaries as part of conservation efforts, and would otherwise be extinct. Many of these islands are off-limits to the general public. Their ecosystems are fragile and the risk of introducing rats and other pests is too great to allow visitors.
Flight in the moonlight
New Zealand snipe or tutukiwi are flightless from day to day. But occasionally, males fly high then plunge downwards so fast that the air vibrates their tail feathers, producing a mysterious roaring noise. They do this mainly on moonlit nights, and the purpose of these aerial displays is unknown. By avoiding flight at other times they are safer from harrier or skua attack, but staying on the ground puts them at risk from rats.
The main threats to native land birds are the mammals that were introduced when people settled the land. The land birds’ strategies for avoiding predatory birds made them all the more vulnerable to predatory mammals. For example, when threatened, the New Zealand snipe flies just a few metres, seeks cover, and then remains stock still, relying on its plumage for camouflage. This keeps it hidden from birds of prey that hunt by sight, but not from mammals following a scent.
The Pacific rat
Losses began with the introduction of the Pacific rat or kiore (Rattus exulans) that arrived with Polynesian settlers about 750 years ago. The fast-breeding rats swarmed across the countryside, devouring small ground-dwelling birds and the eggs of ground-nesting birds.
Humans drove the large land birds, including all moa species, adzebills (Aptornis otidiformis and A. defosser), land geese and Finsch’s duck (Chenonetta finschi) to extinction. Relatively easy to hunt, these flightless birds were a staple food for early Māori until none remained.
A second wave of extinctions began in 1769 when European voyagers and then settlers introduced two larger species of rats (Rattus norvegicus, R. rattus), cats (Felis catus), stoats (Mustela nivalis), ferrets (M. furo), possums (Trichosurus vulpecula) and other predators. Birds that had evolved in the absence of mammalian predators simply stood no chance.
Competition for food and land
Competition from mammals such as possums and deer reduces the food available for kōkako, takahē and other endemic birds. Competition from humans, who have taken land to produce food, has led to widespread and rapid loss of wetlands and forests. Over 90% of New Zealand’s wetlands and two-thirds of its forests have been lost since the first human settlement, much of it in the last 180 years. While a lot of forest remains, most of it is at high altitudes or in the wetter western parts of the country. Meanwhile the dry lowland forests of eastern New Zealand, once biologically diverse, have essentially disappeared.
Loss of endemic birds
Endemic species are more vulnerable than other native species. Particularly at risk are those that belong to families or orders found only in New Zealand (the most distinctive and unusual species). Nearly all of these are threatened, endangered or extinct. New Zealand has lost many of its unique taonga, and is in danger of losing more.