The Forest Bridge Trust – Local kiwi expansion

The North Island brown kiwi on a rare daytime foray. Photo, Save the Kiwi.

The Forest Bridge Trust’s ecologist Dr Virginia Moreno has announced some encouraging results from her team’s winter kiwi monitoring efforts. She says there is clear evidence that kiwi populations are expanding at Mataia and Tāwharanui. Both translocated populations have steadily grown in recent years, reaching high densities.

Although Tāwharanui’s predator-proof fence extends to the low-tide zone, there are always times when coastal access is possible. It’s a vulnerability which can be exploited by pests, such as rats and mustelids (stoats, weasels and ferrets) entering the sanctuary, but also kiwi which are exploring the perimeter of the sanctuary.

In anticipation of kiwi dispersal beyond the park, The Forest Bridge Trust has intensified mustelid control in the buffer zone surrounding Tāwharanui and has encouraged local dog owners to participate in dog training for kiwi aversion. There have been several records of kiwi in the buffer zone and we wanted to investigate how many kiwi are living outside the park and how well they are doing. The results exceeded our expectations.

During the official monitoring season, 487 kiwi calls were detected at eight of the 12 acoustic recorders deployed up to six kilometres beyond the predator-proof fence. Several male-female duet calls were recorded, indicating active breeding of at least four pairs. One site had a relatively high call rate of 4.2 calls per hour, very close to the five calls per hour typical of high-density kiwi populations. Additionally, the average call rate at three sites monitored since 2021 has tripled in just two years.

These results provide clear evidence that several kiwi pairs are living and breeding in the buffer zone, and we can expect this population to continue growing and expanding. With these promising results, residents in the Takatu Peninsula can anticipate seeing and hearing more kiwi in the coming years.

On the west coast, the news is just as encouraging. Monitoring of the buffer zone at Mataia has provided exciting indications of kiwi expansion. Acoustic recorders have picked up numerous calls at a site located east of SH16, revealing the growing presence of kiwi. Most astonishingly, a kiwi was detected by one of our monitoring trail cameras at a site in Makarau, nearly seven kilometres from Mataia.

With kiwi now extending their territories on both coasts and the mustelid-controlled bridge well underway, the dream of connecting the eastern and western kiwi populations is drawing closer to reality. However, it is crucial to stress the need for ongoing trapping and dog control, even in areas where kiwi sightings have not been recorded. Juvenile kiwi are known to be intrepid wanderers, often covering several kilometres before settling down, and it is anticipated that several of them will be looking for new homes in the coming year.