Kiwi - in dire straits by David Speir and John Ogden
Environmental News Issue 13
Some of the points made this article we first published in our second edition of this magazine. Since that time (January 2005) the plight of kiwi in NZ has steadily worsened. Now, more than ever, the possibility of GBI as a kiwi sanctuary needs to be explored as a major area of survival for this, our most iconic species.
Several species of kiwi evolved in the mammal-free Aotearoa of pre-colonisation into the most mammal-like bird on the planet: flightless and nocturnal, with external nostrils at the end of a long bill and an exceptional sense of smell. Kiwi also have mammal-like bone marrow, large ear openings and loose hair-like feathers. The female lays proportionately one of the largest eggs of any bird, which the male then incubates for 70-85 days. This reversal of roles is associated with monogamy, a combination which is extremely rare among birds.
The arrival of man brought introduced mammalian predators which have decimated the kiwi’s breeding success and continue to dramatically erode the adult populations. It is estimated that today’s total population represents some 0.05% of the population before the arrival of humans (and rats). Now every species is classified (by the Dept. of Conservation) as “threatened”—some more, some less, e.g. the North Island brown kiwi (although seemingly numerous at 20,000 (est.) individuals) is in Category 4—Serious Decline.
Research has shown that the brown kiwi’s average life expectancy in Northland is 13 years, whereas in other parts of NZ kiwi have been calculated to live for 50 years. The impact of straying dogs is halving their adult population every 10 years and decimating recruitment of juveniles. Stoats are preying on the diminishing number of chicks with devastating success.
The Whangarei Kiwi Sanctuary (WKS) has released some tragic statistics from monitored populations in their sanctuary. The data indicates a worsening trend for kiwi populations near human settlement.
• Kiwi deaths in the WKS have increased by 23% from the 2005 to 2006.
• 75% of adult kiwi that died in the WKS during the 2005/06 breeding season were killed by dogs, up from 50% during the previous season.
(These statistics are based on fairly small numbers, but indicate a definite trend.)
Forest and Bird Organisation2 in their website piece “Kiwis facing Extinction” put it bluntly:
“The situation is urgent. All mainland species of kiwi are threatened with extinction unless the causes of the decline are addressed. Based on present trends, kiwi could be extinct on the mainland in about fifteen years —with the exception of five D.o.C kiwi sanctuaries and community ‘kiwi care’ efforts. Kiwi are already extinct in many areas, such as the Manawatu, Wairarapa, Horowhenua, Marlborough and most of Canterbury and Otago. There is a 3-6 year window to choose which remaining kiwi populations we save and which we allow to become extinct. Unless the survival rate improves, the kiwi’s decline will accelerate as existing adult kiwi age and die. Populations without extensive predator control do not produce enough chicks to replace the old kiwis as they die of old age.”
Forest and Bird have identified “a shortage of money” as the single most important barrier to kiwi conservation. These high costs include:
• The cost of establishing and operating sanctuaries
• Research on effective control of ferrets, stoats and cats
The issue of saving kiwi seems largely a political matter, although it must be pointed out that there is no “magic bullet” on the horizon for the control of ferrets, stoats and opossums.
Enter GBI—for the reasons outlined by John Ogden’s in the following submission—the island of Great Barrier already has huge advantages as a sanctuary: no mustelids or possums, suitable habitat, and the potential for effective dog control. The huge costs of creating and maintaining “mainland island” type of sanctuaries do not apply here—we have a moat around us. A kiwi sanctuary on GBI is an economically achievable reality.
Straying and wild dogs have been identified as the biggest single predator of kiwi. Taborski3 an Austrian scientist, documented an episode in Waitangi Forest (1988) where a single dog killed about 500 kiwi in a few months. This is not an isolated incident. Of a reported 194 kiwi deaths in Northland, there is documented evidence of 130 cases of dogs killing kiwi—feral dogs, wandering pets, farm dogs and hunting dogs.
When questioned on the topic, Great Barrier Island dog owners invariably reply that their dogs do not roam, are kept in at night, and are “not even interested in birds” as many have done the bird aversion training. Well and good, so we will point the finger at visitors’ dogs who might take responsibility for the reported deaths this summer of little blue penguins (Tryphena), oystercatcher adults and chicks (Medlands), and possibly cooks petrels (Tryphena). These visiting animals could be banned overnight if the political will existed. The control and management of local dogs could be improved at the same time to contain any ‘ferals’ without undue impact on the lives of responsible dog owners.
Apart from the issue of dogs, the absence of mustelids (stoats, ferrets) on GBI is a huge plus for kiwi breeding outcomes: research identifies a kiwi’s first year as the most vulnerable period, when stoats and cats kill about 95% of juveniles. Population decline would cease if about twenty per cent of young kiwi survived to adulthood. Kiwi can bounce back from this base as they live for about thirty years and can lay up to 100 eggs in a lifetime.
The creation of a Kiwi sanctuary on GBI will not require any mass toxin drop, will not require invasive quarantine measures and will not inconvenience a single responsible dog owner. It could however ensure the preservation of threatened kiwi species, ensuring our national bird and symbol survives the invasion of humankind and our animal followers.
It is time to take action on this — the advantages of GBI as a kiwi refuge far outweigh any possible disadvantages. The benefit to conservation, and to the local economy through eco-tourism should ensure strong community support.
References
1. Northland Kiwi Newsletter, Feb 2007, NZ Landcare Trust
2. Royal Forest and Bird Protection Society, Kiwis facing Extinction website pp www.forestandbird.org.nz
3. Robertson, H.A. 2003: Kiwi (apteryx spp.) Recovery Plan 1996–2006, Department of Conservation, Wellington.
4. Miller P.J. and Pierce R.J. Distribution and decline of the North Island brown kiwi (Apteryx australis mantelli) in Northland, Notornis 42, 203-211 (1995)