Little spotted kiwi: Paradise Regained or Paradise Lost?

Forest and Bird, Volume 16, Issue 1, 1 February 1985, Page 15

Little spotted kiwi: Paradise Regained or Paradise Lost?

Ts its Kapiti Island sanctuary a Garden of Eden or not for this endangered species? Jim Jolly, Wildlife Service Screntist, reports.

Atte the kiwi is the best known and most unusual of New Zealand’s array of intriguing flightless birds, the decline of the smallest species, the little spotted kiwi, went almost unnoticed until the late 1970’s. This was partly due to the difficulties of finding and identifying a nocturnal, forest bird like the kiwi. The similarities, both in calls and appearance, between great and little spotted kiwis result in many doubtful field and museum records. It now seems the last specimen of little spotted kiwi was collected in Southland in 1938. Since then a pair of leg bones from a recently dead little spotted kiwi were recovered in Fiordland in the early 1970’s. Apart from a single feather, also from Fiordland, there are no other recent confirmed reports of little spotted kiwis from the mainland of New Zealand. The only substantial population is that on Kapiti Island. Although there is still the possibility of finding odd individuals in the South Island, the only other little spotted kiwis known were, until recently, on D’Urville Island. That population dwindled and three birds, all that could be found, were removed from the island ‘and away from the predators found there vs stoats, pigs, pig-dogs and cats. It has. always been assumed that Kapiti’s little spotted kiwi population originated from a release of kiwis in 1912. If this was the origin of the population then the bird is a remarkably adaptable animal. Early this century about two-thirds of the

island was cleared for grazing. Feral stock, including hundreds of goats, roamed over the island depleting the forest understory. Possums, Norway rats, kiore (the Polynesian rat) wekas and even some cats had all been introduced and threatened the kiwis’ survival either by predation, particularly on eggs or chicks, or by competition for food and shelter. An alternative possibility is that the bird persisted on the island from the last ice age, marooned from the influences that brought about this kiwi’s demise on both sides of Cook Strait late last century. Whatever the origin of the kiwis on Kapiti, the species clearly has the resilience to adapt to new conditions. On the other hand, given this adaptability, its disappearance on the mainland was presumably caused by factors not present on Kapiti, such as predation by stoats. My Wildlife Service colleagues began research on little spotted kiwis in the mid-1970’s. Initially, South Island reports were checked, the Kapiti and D’Urville Island population were assessed, and birds were sent to the Otorohanga Kiwi Centre where there had been success with breeding brown kiwis. The two males of the three D’ Urville Island little spotted kiwis were sent to Otorohanga but failed to settle into captivity, as birds from Kapiti had done, and one died. The second male was then sent to Maud Island to join the female but, although apparently established, it eventually disappeared. In July 1982, follow-

ing the devastating news of the arrival of stoats on Maud Island, the female was moved to another island in_ the Marlborough Sounds, along with two males from Kapiti, in an attempt to preserve as much of the genetic diversity of the species as possible. Again the kiwis appear to have established but we have been unable to detect any signs of breeding success in the dense forest of the island. The selection of suitable islands for transfers of the kiwis is a part of an intensified research programme on the little spotted kiwi begun in 1980. Apart from assessments of suitable islands and investigation of this kiwi’s foods and other habitat requirements, the aims of this research are to determine the size and health of the Kapiti population. Using the knowledge that kiwis call loudly and often, we developed a technique for estimating the number of kiwis on the island from the position and number of calls. By counting calls from the same listening points for two years we found how kiwi calling varied with time of night, time of year and weather. Then the Service’s eight-man Fauna Survey Unit spent a month working from one end of the island to the other recording calls. There was clearly a dense population widely distributed throughout the mosaic of forest types on the island. By relating the number of calls heard from a known number of birds in the study area, we were able to calculate the number of birds on the rest of the island from the number of calls

heard. The results suggest over 1000 birds were present and, since it is primarily the territory holders that call, this is an estimate of the size of the breeding population. The little spotted kiwi’s endangered species status, then, comes more from its vulnerability in being confined to one island, rather than from just its population size. This kiwi certainly has its stronghold on Kapiti Island, but over the last five years a disquietening trend has emerged: very few chicks hatch. In one of our study areas that embraces regenerating forest, typical of two-thirds of the island, there appears to have been no breeding success at all. We think this has much to do with the island’s wekas. In the first two years of study, nest burrows were found by laborious searching through the study areas. We found five nests with broken eggs and only two incubating kiwis. These two soon lost their eggs. We came across a weka carrying offa kiwi egg, having stabbed through the shell and downed most of the contents. On another occasion I arrived at a kiwi nest to find a weka eating the egg from beneath the incubating kiwi! Over the last three seasons we have been able to assess how many eggs are lost by monitoring the breeding of up to ten pairs of kiwis with the aid of radio-telemetry, a video nest monitor, and the efforts of an extremely hard-working field team led by Rogan Colbourne. We found that probably all of the ten pairs had nests with

eggs each year, some pairs had replacement second nests, but only two chicks have hatched. Wekas have preyed on at least one third of the nests but, judging by the type of damage to eggs, another third of the nests have probably suffered the same fate. The male kiwi, who alone incubates, leaves the nest unattended each night and occasionally for whole days, with only sticks or leaves pulled over the entrance. The bird seems peculiarly vulnerable to the weka, our native ground predator, who is well capable of making the most of these opportunities, even to the extent of seizing the eggs at night when the kiwis are active. Little spotted kiwis had to contend with wekas in their natural range but the density of wekas on Kapiti is very high, perhaps much higher than it ever has been on the mainland. In addition, the younger regenerating forest on Kapiti does not have the ground cover of old logs and stumps that would conceal a nest burrow in older forest on the mainland. Predators most probably also attack chicks, since chicks do not follow their parents in the evening at foot and even leave the nest independently of the adult. We have found seventeen chicks in four seasons of all-night ‘‘chick patrols’’ but have little idea of how many survive to breed themselves. The indications are that, with this rate of egg loss, the population can only avoid going into decline if not only adults live for an average of 20 years but also as many as 50 percent of the chicks survive to become breeders.

Neither is likely, even though the kiwi is a long-lived bird. Future research is designed to test these ideas and a decision will then have to be made as to whether or not wekas should be eradicated from the island. Whatever the outcome, the importance of the island transfer programme is clear. Red Mercury (206ha) and Hen Islands (476ha) have been checked and look to be excellent for little spotted kiwis. The first step in this programme was taken in July 1983 when six males and six female kiwis were flown from Kapiti to Red Mercury. Subsequent visits to Red Mercury indicate the prospects for the birds are good as at least three pairs have established. This transfer, along with a proposed release on Hen Island, will be important stepping stones in the programme, but the Wildlife Service can only feel the future of the little spotted kiwi is safe once they are on larger islands where a population similar to that on Kapiti could establish. Only Little Barrier and Codfish Islands of the larger islands are free from mammalian predators. The present size of the Kapiti population allows for ample birds for these transfers. It is also the right time to be finding out about the poorly understood biology of this bird, rather than as so often happens with endangered species, at a time when numbers are critically low and most of the effort must be concentrated on management that is, of necessity, all but desperate in its approach. oe