Annual Kiwi Call Survey

Author: Janet PetricevichDate: 03/05/23

Kiwi pukupuku/ little spotted kiwi were first introduced to Tiritiri Matangi in 1993 (10 birds) with a further 6 released in 1995. Two birds were lost early on but 14 went on to contribute to the genetic pool.

As part of the population monitoring of this translocated species, Supporters of Tiritiri Matangi first conducted a kiwi call survey in 2009 and have subsequently done so in March of every year, apart from 2012, 2015 & 2020.

During the survey, Supporters of Tiritiri Matangi volunteers are stationed at ten listening spots around the island. The survey starts twenty minutes after sunset and lasts for two hours. Listeners record the time a call is heard, the sex of the bird calling and the compass bearing and approximately distance of the call, from the listening site. The listening sites are the same from year to year and the survey takes place when there is no moon during the survey hours.

Left: Photo taken during the 5-year survey.Right: Janet holding a kiwi during the 5 year surveyPhoto credit: Janet Petricevich

The survey is conducted to collect trend data on approximate kiwi numbers and by surveying every year, we can pick up short-term variations. There is also value in the survey enabling Supporters of Tiritiri Matangi volunteer participation.

Listeners also record ruru/ morepork call during the survey. John Stewart surveys ruru numbers during their breeding season and recording call locations during the kiwi call survey helps him identify areas of bush where ruru are holding territory.

There are some challenges for the survey volunteers. Fearing the dark is an instinctual survival mechanism for humans, so standing alone, outside on the island at night can sometimes bring on a mild case of the heebie-jeebies. Some nights can be bitterly cold, especially if there is wind, and boredom can creep in if the listening site is less active for calls. Conversely, if the site is very active, it can be challenging to record calls coming in quick succession. Differentiating male & female calls can also be tricky when the wind is stronger or if the calls are heard a long distance away.

Offsetting the challenges, there are also some pleasures of being out at night on the survey. There is often quiet time to appreciate the night sky and the calls or sightings of other island nightlife such as insects, reptiles and sea birds. The occasional close encounter with kiwi is always a highlight.

In addition to the annual kiwi survey, a 5-yearly survey is conducted in conjunction with the Department of Conservation Dogs NZ. During this survey, kiwi are caught & banded. The 5-yearly survey gives a more accurate indication of numbers but is more expensive and logistically challenging to organise.

The last 5-yearly survey took place in 2022 and estimated the kiwi population on Tiritiri Matangi to be around 80 birds.

and one from the 2017 translocationPhoto credit: Janet Petricevich

Kiwi pukupuku calls

Male & female kiwi calls are different. The male gives a high-pitched ascending whistle, whilst the female gives a slower and lower-pitched ascending trill. Both sexes repeat their calls up to 35 times per sequence.