The kiwi, a unique flightless bird, is an enduring symbol of New Zealand’s natural heritage. Revered as a national icon and a treasure (taonga) by Māori, the kiwi’s survival is a significant conservation concern.
The Current Kiwi Population
New Zealand’s overall kiwi population is estimated at 68,000 birds. Unmanaged populations decline by about two percent annually, or 20 birds per week. Five recognized species exist: the North Island brown kiwi, Great Spotted Kiwi (roroa), Little Spotted Kiwi (kiwi pukupuku), Rowi, and various forms of Tokoeka. Their conservation status ranges from ‘Recovering’ to ‘Nationally Critical’.
The North Island brown kiwi is the most common species, and recent efforts have shown positive results, with an estimated increase of at least 7,000 birds in managed areas over the last four years. This species is now classified as ‘conservation dependent’, indicating its reliance on ongoing protection. The Little Spotted Kiwi, while classified as ‘Near Threatened’, has a significant portion of its population, approximately 1,350 individuals, thriving on Kapiti Island. In contrast, the Rowi is ‘Critically Endangered’, with only around 450 individuals remaining.
Tokoeka kiwi, including forms like the Haast, Fiordland, and Rakiura (Stewart Island) tokoeka, collectively numbered about 30,000 in 2012. The Haast tokoeka is Nationally Vulnerable, while the Southern Fiordland tokoeka is Nationally Endangered. Some Fiordland tokoeka populations have shown a two percent annual growth rate in areas with active management.
Challenges to Kiwi Survival
The decline in kiwi populations is primarily due to introduced predators, habitat degradation, and human impacts. New Zealand’s native wildlife evolved without mammalian predators, making kiwi vulnerable to species brought by humans. This lack of natural defenses has significantly impacted their numbers.
Stoats are a major threat to young kiwi, responsible for roughly half of all chick deaths on the mainland. Chicks remain vulnerable to stoat predation until they reach a weight of about 1 to 1.2 kilograms. For adult kiwi, dogs pose the greatest danger, and even playful encounters can result in fatal crushing injuries due to the kiwi’s unique anatomy. Feral cats also prey on kiwi chicks, and ferrets can kill adult birds. In areas without predator control, only about 5 to 10 percent of kiwi chicks survive to adulthood.
Habitat loss and fragmentation further compound these challenges. Historically, vast areas of New Zealand’s forests were cleared for agriculture and human settlement, reducing forest cover from 85 percent to about 23 percent. This resulted in isolated habitat patches, forcing kiwi and predators into smaller areas with more frequent encounters and scarcer resources. Human activities like road accidents also account for kiwi fatalities. Small, isolated populations face reduced genetic diversity and increased susceptibility to diseases and environmental changes.
Protecting Kiwi Populations
Conservation efforts are underway to protect kiwi populations across New Zealand. These strategies involve predator control, captive breeding, safe havens, and translocation programs. These multifaceted approaches are reversing the decline in many areas.
Predator control is central to kiwi protection, utilizing methods like trapping and the controlled use of toxins such as 1080. These programs significantly increase chick survival rates, with some managed areas seeing 50 to 60 percent of chicks reaching maturity. Sustained predator control in the Coromandel region, for example, led to a 10 percent increase in brown kiwi populations between 2015 and 2020. The national Predator Free 2050 initiative aims to eliminate introduced pests, providing a long-term solution for native wildlife.
Captive breeding programs, like Operation Nest Egg (ONE), are crucial. Under this program, kiwi eggs are collected from the wild, incubated, and hatched in captivity. Chicks are raised until they reach a “stoat-safe” weight of 1 to 1.2 kilograms before release into protected wild areas. This process greatly improves a chick’s chance of surviving to adulthood from 5 percent to about 65 percent. The Kōhanga Kiwi strategy establishes predator-free “nursery” sites, often fenced sanctuaries or islands, where young kiwi can mature without threat.
Kiwi sanctuaries and predator-free islands serve as secure environments for population growth. The Department of Conservation established five such sanctuaries in 2000, and offshore islands act as natural refuges where introduced predators have been removed. Kiwi are often translocated to these safe areas to establish new populations or bolster existing ones. Translocation efforts have reintroduced kiwi to areas where they had been absent for decades, such as parts of Wellington. Community involvement, including over 90 iwi-led and community groups, is integral, with public awareness campaigns and dog avoidance training contributing to conservation successes.