A comprehensive new survey has provided the clearest picture yet of the North Island brown kiwi living on Kawau Island (Te Kawau Tūmaro-o-Toi), confirming both the uniqueness of this population and the challenges it faces.
Undertaken between January and March 2025 on behalf of Auckland Council, the survey, utilising a detection dog, is the first to directly assess the health, structure and genetics of kiwi on the island. It builds on more than three decades of earlier listening surveys, acoustic recorders and even a thermal camera study, all of which confirmed kiwi were present on Kawau, but left many questions unanswered.
Those questions are now starting to be filled in. Across three survey trips, trained kiwi dogs detected 56 birds, with 51 kiwi safely handled by the team. All were adults, many in moderate to poor body condition, and no chicks or juveniles were found.
Auckland Council’s Project Manager Lisa Tolich says the survey gives essential baseline information that simply wasn’t available before.
“Following our recent forest ecosystem monitoring work, the North Island brown kiwi health and demographic survey on Kawau Island has provided valuable insights. It helps us understand how habitat condition and pests are affecting kiwi and it will guide future habitat restoration and management priorities.”
The absence of young birds during the survey suggests low breeding success and limited recruitment into the adult population in recent years. Dry environmental conditions, habitat degradation and heavy browsing of the forest undergrowth by wallabies are all likely contributing factors, reducing food availability and putting pressure on adult birds.
Genetic sampling has also revealed Kawau kiwi have very low genetic diversity, with many individuals closely related. This reflects the population’s origins, believed to trace back to a small number of birds introduced from the Hokianga in the 1860s, with possible additional introductions decades later. While some unique genetic traits remain, long-term isolation raises concerns about in-breeding and resilience.
Save the Kiwi who carried out the survey on behalf of Auckland Council says the findings highlight both urgency and opportunity.
Tineke Joustra, Operations Manager of Save the Kiwi says Kawau Island’s kiwi are a particularly special population with their unique genetic history.
“Our recent survey shows the population is healthy, but that its long-term resilience would benefit from a carefully managed genetic exchange. That means creating space by moving some birds to other suitable sites, while bringing new genetics onto the island at the same time.
“With the wallaby eradication currently underway, we’re also looking forward to the undergrowth regenerating and hope this improved habitat will support higher chick survival and, over time, more young birds on the island.
“This research allows us to plan smarter, look at habitat improvement, wallaby control and carefully managed translocations to strengthen the population while also protecting its unique genetics.
The survey was carried out under Save the Kiwi’s Wildlife Authority and funded by Auckland Council’s Natural Environment Targeted Rate. Regular monitoring and integrated genetic planning are now recommended, positioning Kawau Island to play a meaningful role in the wider recovery of kiwi across New Zealand.