Cape Sanctuary General Manager Rachel Ward on the latest release of Kiwi back into the wild.
A significant spike in Hawke’s Bay’s kiwi population has been attributed to the changing habits of young birds and conservation efforts, with a recent call count listening survey revealing one of the most considerable indications of growth in nine years.
Leading conservationist Dr John McLennan of the Maungataniwha Kiwi Project said rigorous overnight call observations reported an average of about 3.6 calls an hour for males and females together.
“That might not sound like a lot, but since 2015, more or less over the last nine years, it’s been hovering at about 1.5 an hour, so more than double.”
Several of the sites surveyed in and around the Maungataniwha area saw close to 10 calls heard an hour, sometimes 20 over a two-hour listening period or better.
“In Hawke’s Bay, it’s very rare to get more than one call an hour. [And] it’s not just one kiwi calling 20 times.”
McLennan said call counting is done by distinguishing the sound of male and female kiwi calls for two hours at a time, using a sample from the same areas every time for three consecutive nights.
“This year is special because the counts have changed, and the numbers are starting to go up.”
Forest Lifeforce Restoration Trust manager Pete Shaw releases a chick from the successful Maungataniwha Kiwi Project into the bush at the trust’s nearby Pohokura property. Photo / FLRT
Kiwi eggs are taken from Maungataniwha and incubated, and the resulting chicks are then reared in safety at the Cape Sanctuary south of Napier or other locations until they are large enough to defend themselves against stoats.
One of its main goals is to secure and enhance the kiwi population in the Maungataniwha Native Forest, promoting natural population growth.
Interestingly, it is already known that kiwi numbers at Maungataniwha reached self-sustaining levels several years ago.
“Juvenile kiwi, if they can find an easy place to live where they don’t have to fight to gain space, they will take that. For a long period of time, the juveniles produced in Maungataniwha were moving out and settling in other neighbouring areas. They took the easy option rather than trying to muscle into places that were already occupied.
“The fringes are already starting to fill up; the easy option doesn’t exist anymore, so they are now starting to muscle in on the areas they are being released. The change is a very genuine one, and you can feel it.”
He said physical signs, not just the call rates survey, were signalling a population increase in the area.
“We are also seeing a lot more kiwi on the roads when we travel at night. There are plenty of signs that indicate the numbers are changing for the better; you can feel it.”
There was additional good news, with patterns showing further population growth is also expected.
“If you look at the parts that are filling up now, it’s placed alongside one particular river where the river is acting like a barrier and preventing leakage out that side. I expect that wave will fill up over the next few years.”
McLennan acknowledged there would always be natural bias, and counts were often underrepresenting actual numbers, but they are continuing to look at new ways of getting concrete results.
“There is potentially a technique we can use call rates to get an absolute estimate, simply based on whether a call is made by a transmitted bird or a non-transmitted bird. You can use that ratio to work out how many are there, which we will be trying next time around.”
He said the science behind call counting was evolving, and Maungataniwha was an excellent place to test the idea.
Mitchell Hageman joined Hawke’s Bay Today in January 2023. From his Napier base, he writes regularly on social issues, arts and culture, and the community. He has a particular love for stories about ordinary people doing extraordinary things.
