Brown kiwi (Apteryx mantelli) have a big nose, short temper and brown, spiky plumage.
All brown kiwi live in the North Island. Four geographically and genetically distinct forms have been identified: Northland, Coromandel, western (mainly Taranaki/Wanganui) and eastern (mainly Hawkes Bay, Bay of Plenty and East Cape).
All population numbers quoted are based on 2015 estimates unless otherwise stated.
Brown kiwi are New Zealand’s second most numerous kiwi species (after tokoeka). Their total population is estimated to be 24,550. However, because unmanaged populations are declining rapidly, it is classified by the Department of Conservation as ‘threatened: nationally vulnerable’, and its future depends on active management to deal with predators.
Brown kiwi are the focus of most community-led kiwi conservation groups in the North Island. These efforts are making an enormous positive difference to the species’ future.
Within brown kiwi, the Coromandel taxa is the most rare, with about 1700 birds. This population is growing thanks to both the Moehau kiwi sanctuary and the community-led kiwi initiatives in the Coromandel. In 2015, most Coromandel brown kiwi were being actively managed – nearly 75% of them – and the population is predicted to grow by nearly 5% by 2030.
Numbers for the other three taxa are similar to each other (between 7150 and 8200 birds). Where they are actively managed, populations are flourishing.
However, in places with little or no management of predators populations are declining. Of all brown kiwi, the eastern taxa has the lowest proportion under active management – 21% of the population – and its numbers are predicted to grow by just 1% over the coming 15 years. Ferrets and stoats are the biggest problem for eastern brown kiwi.
Generally the news for brown kiwi is positive, with predictions that, over the next 15 years, total numbers for all four taxa will increase.
The table below shows the estimated brown kiwi populations in 2008 and 2015, and what they could be in 15 years time. The numbers assume that unmanaged mainland populations will decline by 3% each year, and that managed populations will increase each year – at more than 2% for the Northland and Coromandel taxa (2.8% and 4.8% respectively), but at less than 2% for eastern and western brown kiwi (1.0% and 1.3% respectively).
|Region||Estimated 2008 population||Estimated 2015
|Eastern – Bay of Plenty, East Coast, Hawke’s Bay||8,000||7,150||7,281|
|Western – King Country, Taranaki, Whanganui||8,000||7,500||9,064|
As with other kiwi species, brown kiwi pairs are generally monogamous – that is, they have only one mate at a time. Monitoring shows that fewer than 5% of eggs don’t belong to both parents.
Brown kiwi also generally mate for life. Divorces do sometimes happen, usually after failed breeding attempts or if the birds are early in their breeding career. One couple, known as Liz Taylor and Richard Burton, divorced and then came back together. Research suggests that birds that divorce once are more likely to divorce again.
Eggs and Clutches
Brown kiwi usually have two eggs in each clutch. While just one egg is not unusual, three is very rare.
Pairs usually have two clutches a season, which means that in a good year they can raise four chicks. Some pairs have just one clutch. Some pairs will lay more than two clutches, especially if their eggs are removed as part of Operation Nest Egg or if lost to predation early on.
Only the male brown kiwi incubates the eggs. He loses about 20% of his body weight during this time.
Brown kiwi chicks are never fed by their parents. They first leave the burrow to feed when 5–7 days old – up until then they are nourished by the large yolk sac, leftover from when they were in the egg. Brown kiwi chicks leave the nest fend for themselves from about 10 days of age, though some return to the nest for up to 70 days. Most finally leave their parents’ nest when about 20 days old.
While the mother stays near the nest while hatching is in progress, only the male parent stays around the young chick when it returns to the burrow each day, to share warmth and maybe protection.
Operation Nest Egg
Brown kiwi have been part of Operation Nest Egg since the tool’s earliest days, beginning in 1993. The tool is now used on all four taxa, with the Coromandel brown kiwi the latest addition.
Research has shown that when eggs are taken, adult brown kiwi lay 30% more eggs over a season. However, if a newly-hatched chick is taken the parents are less likely to lay another clutch. That means taking eggs rather than newly-hatched chicks boosts kiwi populations more quickly because the adult birds are more likely to lay again.
Monitoring has revealed no evidence that Operation Nest Egg increases the likelihood of divorce—there had been a concern that pairs may have treated the eggs’ disappearance as breeding failure, which can cause divorce.
Several kohanga kiwi populations exist or are planned for brown kiwi. You can read about them here.
Brown kiwi seem to prefer lowland and coastal native forest – their population density is highest in these areas. However, they are also found in sub-alpine areas – at the Chateau in Tongariro National Park, and near the bushline at Mt Taranaki. Huge changes to New Zealand’s original forest cover mean they have had to be adaptable.
Today brown kiwi live in many different types of vegetation, including exotic forest plantations and rough farmland. While this may seem surprising, plants growing under Pinus radiata trees often support native species, which means the soils provide an ample supply of insects for kiwi to eat.