Night Parrot (inappropriate as it is the name of an unrelated Australian species).
DESCRIPTION Length 64 cm. Weight males 1.5–3.0 kg, females 950 g–1.6 kg.
The Strangest Parrot in the World | Modern Dinosaurs
ADULTS Upperparts bright green irregularly barred and streaked dark brown and yellow; underparts greenish-yellow irregularly barred paler lemon-yellow and light brown; variable yellow superciliary band; forehead and facial disc yellowish-brown, feathers with paler centres and darker tips; wings and tail dull green barred brown and dull yellow; bill pale grey becoming horncoloured on lower mandible; iris dark brown; legs bluish-grey in males, pale pinkish-grey in females. 10 males: wing 265–284 (272.6) mm, tail 203–250 (222.6) mm, exp. cul. 34–43 (38.0) mm, tarsus 45–57 (51.8) mm. 10 females: wing 252–285 (269.1) mm, tail 205–238 (220.3) mm, exp. cul. 35–37 (36.4) mm, tarsus 46–56 (49.6) mm. JUVENILES Like adults, but general plumage colouration duller; forehead and less prominent facial disc more brownish, less yellowish; pointed, not rounded tips to outermost primaries; bill pale yellowish-white. DISTRIBUTION New Zealand, were formerly widespread on North, South and Stewart Islands, but now present on only three
offshore islands – Anchor and Codfish Islands in the south, and Little Barrier Island in the north. GENERAL NOTES Oliver (1955) noted that the Kakapo was mentioned by Ernst Dieffenbach in his Travels in New Zealand,
published in 1843, but he had not seen a specimen, and the first
the specimen to reach Europe was collected at Dusky Sound, South Island, and forwarded to England in 1845. Another specimen collected at Milford Sound, South Island, in 1851, was presented to the British Museum and, in 1861–1862, Julius von Haast and James Hector found the parrots to be quite numerous along the west coast of South Island. In the second edition of his A History of the Birds of New Zealand, published in 1888, Walter Buller referred to the Kakapo as being remarkable and made reference to the comment made by Philip Sclater, then-Secretary of the Zoological Society of London: This is one of the very remarkable forms peculiar to New Zealand, and has been appropriately termed an Owl Parrot. Dr Sclater refers to it as ‘one of the most wonderful, perhaps, of all living birds’. As its name Stringops indicates, its face bears a superficial likeness to that of an Owl. In all the essential characteristics of the structure, it is a true Parrot; but in the possession of a facial disk (in which it differs from all other known parrots), in the soft texture of its plumage, and
especially in its decidedly nocturnal habits, it betrays a striking resemblance to the Owl tribe. The more we learn about this amazing parrot, the more appropriate becomes the statement by Sclater. That the Kakapo is unlike any other parrot in appearance and behaviour was brought home to me in September 1976, on Maud Island, where I observed males that had been brought to the island from Fiordland. Their large size, strong legs and feet, and cryptic plumage colouration are features indicative of a terrestrial lifestyle and, while watching a bird moving through the undergrowth in a peculiarly shuffling manner, I was left with the impression that here indeed was a parrot that had survived virtually unchanged
from ancient times in an isolated environment without predators. STATUS Subfossil bones show that prior to Maori settlement in New Zealand, approximately 1300 years ago, Kakapo were widespread on North and South Islands, being most common in high rainfall areas west of the most divide where rimu Dacrydium cupressinum and Nothofagus beech trees dominated the forest canopies Worthy and Holdaway 2002. Subfossil remains have not been found on Stewart Island, so it has been suggested that
the population there may have originated from liberations by Maori in pre-European times or from Fiordland birds liberated there in the 1880s (Powlesland et al. 2006). The range contracted substantially after Maori settlement, especially in North Island.
Tipa (2006) notes that dogs were used by Maori hunters to capture and kill the parrots for meat, skins and feathers. The meat was regarded as a delicacy, feathers were used for head adornments, and skins with the feathers intact were softened to make dress capes and cloaks. Dogs became feral and, together with Pacific Rats or kiore Rattus exulans, probably initiated a long history of predation by introduced mammals. Widespread burning of forest, scrublands and tussock grasslands by Maori may have caused local extinctions, especially in drier eastern and central
regions of South Island (Powlesland et al. 2006).
At the time of European colonisation during the late 18th century, Kakapo still occurred in parts of central North Island, and were reported from the Hunua Range, south of Auckland, as late as 1912 (McKenzie 1979). They were extinct in eastern regions of South Island, but remained common in some higher-rainfall areas in northern, western and southern regions (Lloyd and Powlesland 1994). Landclearance by European settlers after the early 1800s probably did not impact significantly on the population because by then the parrots already were confined to scattered remote areas, and predation by feral cats, together with habitat destruction by feral herbivores, probably were responsible for only local declines. After 1880, the situation changed dramatically when the introduction and establishment of three species of
mustelids, Black Rats Rattus rattus, several species of deer, and Australian Brush-tailed Possums Trichosurus vulpecula brought about a rapid decline. Predation by mustelids undoubtedly was the main cause of this decline, with the spread of Black Rats, which would have taken eggs and chicks as well as competed with adults for food, being a contributing factor. Competition for food and habitat degradation by deer and possums would have inhibited successful breeding. By the early 1900s, Kakapo had become extinct in North Island and had disappeared from northern parts of South Island, with the last remaining stronghold confined to remote subalpine valleys in Fiordland in southwestern South Island. Decline in the Fiordland population had been noted in the late 1800s, and it also succumbed to the same pressures of predation and habitat degradation, so that by the 1970s it was reduced to a few aged males scattered in less accessible parts of a few remote valleys (Merton 1985; Butler 1989). Of 18 males found in Fiordland during the 1970s, five were transferred to
offshore islands, and none of the remaining 13 are known to have survived beyond 1987 (Clout and Craig 1995).
Earlier reports of sightings of Kakapo on Stewart Island were investigated in 1977, and a population estimated to comprise between 100 and 200 birds of both sexes was found in an area of some 8000 ha of modified scrubland and forest (Powlesland et al. 1995). There are no mustelids on Stewart Island, but feral cats are present, and evidence of predation by feral cats was recorded, with the remains of 15 Kakapo killed by cats being found during 1980–1982 (Best and Powlesland 1985). The predation rate on radio-tagged adult Kakapo reached 56 per cent during 1981–1982, so an intensive cat control program was commenced in 1982, and no further remains of cat-killed Kakapo were found. However, to ensure survival of remaining birds, 38 males and 24 females, the total number that could be found, were translocated to islands free of mustelids and cats, but not Pacific Rats. The last accepted record for North Island was from the Huiarau Range in 1927, the last South Island record was of three males in
Fiordland in 1987 and the last record for Stewart Island was of a female found and transferred to Codfish Island in 1997. Kakapo now are extinct in their natural range, and all surviving birds are in intensively managed populations on three offshore islands. In 1995, the population reached its lowest level, with just 30 males and 21 females surviving, but in that year the introduction of new management procedures, including the eradication of Pacific Rats from Codfish Island, the provision of food supplements to nesting females, and intensive monitoring with intervention when necessary, brought about a significant increase in nesting success (Elliott et al. 2006). Furthermore, the survival of adults on these islands has been remarkably high, averaging only about 1.3 per cent mortality per annum. In November 2005, the population
comprised 45 males and 41 females. with 40 or 45 per cent being reared on the islands. At the time of writing the population of 125 birds comprises many younger birds and an equal ratio of males and females. All females are from Stewart Island, and the resulting lack of genetic diversity has given rise to high levels of infertility, which is a major problem inhibiting the recovery effort. On average only 60 per cent of eggs are fertile, and in the 2014 breeding season the fertility level dropped to 40 per cent. Artificial insemination is being used in an effort to improve the fertility rate and, if the behaviour of sitting females causes concern, their eggs are taken for artificial incubation. Wherever possible chicks
are reared by their mother or by a foster mother, but they will be handreared if necessary. The Kakapo is listed on Appendix I of the Convention on International trade species of untamed Fauna and Flora (CITES).
HABITATS Williams (1956) noted that Kakapo occurred in higherrainfall areas up to 1250 m, and primarily were birds of the mossy Nothofagus forest, especially where these forests adjoined open country along river flats or the subalpine scrub belt bordering meadows of Danthonia tussocks above the tree-line. Williams also cautioned that records of higher abundance at altitudes of 1000 m and above may be a reflection of signs of their presence, namely tracks, bowls and chewed vegetation, being more easily detected in less densely vegetated places. There were occasional sightings in predominantly podocarp forest, but such occurrences were few. Other authors make mention of a prevalence of Rimu
Dacrydium cupressinum, a favoured food tree, in preferred habitats. Atkinson and Merton (2006) report that in February–March 1974, ground traverses, line transects and aerial photographs were used to describe and map the home ranges, or more appropriately the ‘core home ranges’, of two Kakapo living in the Esperance River valley, Fiordland, South Island. The first home range of only 1.8 ha was at an altitude of approximately 700 m on a gently sloping river terrace on the right bank of the river, well above normal flood levels and on the more sunny side of the valley. Averaging a metre in height, scrub featuring snow totara Podocarpus nivalis and of varying composition covered most of this home range, with 90 per cent of the canopy comprising shrubs and the groundcover consisting of grasses, herbs, mosses and ferns. Some 51 per cent of the shrubs were species with succulent berries, including Coprosma, Gaultheria and Coriaria shrubs and weeping matipo Myrsine divaricata, with tall Chionochloa tussocks scattered throughout and herbaceous plants abundant in the groundcover. The more intensively used central part of the range was characterised by a significantly lower canopy, together with an increased prevalence of turpentine bush Dracophyllum uniflorum and a lower abundance of muttonbird scrub Brachyglottis rotundifolia and weeping matipo. The distribution of feeding signs, feathers and droppings, as well as nocturnal observations, indicated that this Kakapo was not penetrating the forest beyond a distance of 500 m, and large tracts of the forest margin showed no evidence of the bird’s presence. Some 4 ha in area, the second home range was at a distance of 0.5 km from the first home range, and at approximately 850 m altitude was sited on a very steep, northwest facing valley wall with shrubland dominated by kiokio fern Blechnum novae-zelandiae and low forest of silver beech Nothofagus menziesii being alternating parallel stands of vegetation up and down the slope. The fern shrubland averaged 0.7 m in height, with 40 per cent of the canopy comprising shrubs, 30 per cent consisting mostly of kiokio fern and mountain flax Phormium cookianum, and the remainder comprising herbs,
grasses and sedges. The forest of silver beech varied in height from 21 m in the lower half of the range down to 6 m at the
treeline and, of the many species in the understorey, Pseudopanax simplex, hupiro Coprosma foetidissima and weeping matipo were particularly common. Where the canopy was more open, muttonbird scrub and juvenile silver beech were present. More than 50 per cent of the groundcover consisted of the mountain kiokio Blechnum procerum, and there were numerous fallen tree trunks, stumps and loose rocks. Foliose lichens were abundant on trunks of the beech trees, and mosses were prevalent on the northern side of these trunks. No part of this home range appeared to be used more intensively than other sections.
On Maud Island, in Pelorus Sound, South Island, seasonal habitat selection by translocated Kakapo was investigated
between December 2000 and October 2001 (Walsh et al. 2006).
Significant selection occurred in summer for lowland indigenous forest dominated by pepper tree Macropiper excelsum, kohekohe Dysoxylum spectabile and nikau Rhapolostylus sapida, and in autumn for treeland scrub dominated by five-finger Pseudopanax arboreus, Rangiora Brachyglottis repanda, and bracken Pteridium esculentum. A 15 ha plantation of Monterey pine Pinus radiata also was preferred in summer, but when foraging in this plantation during the night, the birds moved to daytime roosts in a narrow band of dense lowland scrub within the plantation. Other habitats, which mostly were more open and included managed and unmanaged pasture were seasonally or totally avoided. Translocated Kakapo now are present on Codfish Island, some 3 km off the northwestern coast of Stewart Island, and here the dominant habitat is mixed podocarp-rata Metrosideros umbellata forest (Farrimond et al. 2006b). Moorhouse and Powlesland (1991) report that on Little Barrier Island, in Hauraki Gulf, North Island, translocated Kakapo prefer wetter, highaltitude areas, and again there was some seasonal change in habitat preferences, with birds occupying lowland kanuka Kunzea ericoides-manuka Leptospermum scoparium forest in winter and moving to higher-altitude northern rata Metrosideros robustatawa Beilschmiedia Tawa forest during summer. HABITS Kakapo is solitary and throughout much of the year, single birds remain in overlapping home ranges of varying sizes.
Early reports of groups of up to six birds found roosting together are likely to have been of family groups or groups of juveniles (in Higgins 1999). On Maud Island, between December 2000 and October 2001, when translocated birds were radio-tracked at night in each of four seasons, home ranges were estimated for four adult males, three juvenile males, and two juvenile females in each season, and for nine females in summer, and it was determined that home ranges varied from 1.8 ha to 145.0 ha, with seasonal variation being in response to patterning of vegetation, and smallest ranges were occupied in winter (Walsh et al. 2006).
On Little Barrier Island, home ranges were estimated at 21 ha to 38 ha in area, and on Codfish Island, where the population was denser, mean home ranges of adult females and recently-fledged juveniles were estimated to be approximately 15 ha, with only one home range of an adult female exceeding 30 ha (in Powlesland et al. 2006). On Stewart Island, home ranges were estimated at 15 ha to 50 ha in area, or 50 ha for males and 100 ha for females
(in Powlesland et al. 2006). It is pointed out that these estimates of home range areas were determined for remnant populations of Kakapo, probably at a lower density than would have occurred in similar habitats when the birds were more numerous prior to the introduction of mammalian predators. In addition to being solitary, kakapo are highly unsociable, and birds of either sex maintain a distance of several hundred metres from their neighbours. Agonistic behaviour includes vigorous chasing, harsh vocalisation and fighting, the last being more prevalent among displaying males. Although vocal rather than visual signals seem to be utilised more commonly to repel approaching neighbours, there are a range of visual displays which have been observed to be given by a few displaying males (in Higgins 1999). When performing a threat display, a bird faces its opponent, raises and holds its wings over its back until almost touching, raises its head and neck feathers with the neck outstretched and the bill partly opened, while making a low, prolonged growl. In response, the defensive bird stands upright while facing its opponent, and has one foot raised in preparation
for striking downwards.
Kakapo are nocturnal and, when not breeding, they normally retreat to daytime roosts about an hour before sunrise, becoming active about an hour after sunset. Routinely sited on steep, damp, shaded, densely vegetated slopes, often with a southerly aspect, favoured roost sites are dark, dry, sheltered from strong winds, sufficiently spacious to allow the bird to turn, and typically are on the ground under dense cover or in natural cavities, such as caves or hollow tree stumps and logs. Birds occasionally will roost on a horizontal branch in the forest understorey or canopy with dense overhead cover, and individual birds often show a preference for roosting either on or above the ground. Some sites may be used repeatedly or irregularly for lengthy periods, and in Fiordland desiccated droppings still remain on the floors of some former roost sites even though the birds died out there about 40 years ago (in Powlesland et al. 2006). There are occasional reports of birds seen feeding during daylight hours in the early morning and late afternoon, and it is probable that these birds were breeding females with month-old chicks in the nest or without access to good supplies of food. On Maud Island, well after sunrise, I watched a bird come to take supplementary food from a feeding tray.
Although flightless and predominantly terrestrial, Kakapo are excellent climbers, using their outspread wings for balance as they grasp branches with the bill and feet to advance up into the higher foliage of trees and shrubs in search of food, and they are quite capable of moving through the canopy from one tree to the next, again with much wing-flapping for balance. The outspread wings are used also to cushion their descent back to the ground. They walk along the ground with a rather rapid jogging gait, and when travelling downhill they can move with surprising speed. When walking, they adopt a near-horizontal posture with the lower rictal bristles in contact with the ground,and it is suspected that sensory perception may be important when traversing unfamiliar terrain in darkness and when feeding at night on certain foods, such as plants with spiny foliage. When travelling longer distances they follow regularly used, well-defined paths, and these paths are characteristic signs of the presence or former presence of the birds, often persisting in districts long after the local population has died out. Individuals of either sex occasionally walk up to several kilometres from their core home ranges to sites where they may remain for several days, weeks or even months, and such long-distance movements may be made to take advantage of a localised abundance of food or because snow cover forces a descent to a lower altitude.
CALLS Except during times of courtship, when displaying males are highly vocal, Kakapo seldom call, though they do have a varied repertoire of notes. In addition to a mechanical bill-clicking, they emit pig-like grunts and squeals, duck-like warks and a donkey-like braying, as well as a characteristic skraark, frequently heard from competing males during courtship, hissing and humming sounds, and harsh screeches (in Powlesland et al. 2006). Females are known to make a ‘hoarse cough’, and when handled females and juveniles produce a series of drawn-out vibrant, croak-like distress calls, whereas males usually are silent. Most frequently heard is the loud, low-frequency, resonant ‘booming’ from displaying males during courtship. From a standing position, the male progressively lowers his head and inflates grossly the thoracic region, simultaneously producing three or four quiet measured grunts on a descending scale at intervals of approximately two seconds. At maximum thoracic inflation, the grunts give way to soft booms, which increase in volume so that maximum intensity is reached after six to eight booms. The loud booms are repeated 15 to 20 times, at intervals of about two seconds, after which there is a gradual decrease in volume during a further 10 to 20 booms. During booming the head
is held low, and often is almost totally engulfed by the inflated airsac. After each booming sequence, the male assumes an erect, alert and motionless stance for some 20 to 30 seconds before repeating the sequence. A local dialect has been detected in ‘booming’, with males in Fiordland consistently producing a disyllabic boom in contrast to the monosyllabic boom from males on Stewart Island (in Higgins 1999). Fiordland males also boomed more slowly and with greater resonance than males on Stewart Island.
DIET AND FEEDING Kakapo are exclusively herbivorous, and an early record of remains of a lizard being found in a crop sample has been discounted. Best (1984) points out that they are versatile feeders with highly variable feeding patterns, and lots of foods are taken opportunistically. This flexible feeding pattern also allows utilisation of a wide spectrum of seasonal foods, some of which may be available only for short periods or in intermittent years. Also, they are selective feeders, not only in their seasonal exploitation of food plants and parts of those plants but also in selecting individual plants. One particular shrub or grass tussock often is selected, but the same adjoining shrubs or tussocks are ignored. The diet comprises leaves or leaf buds, twigs or stems, bark, nectar, fruits, seeds, fern pinnae, roots and rhizomes or tubers, and moss or fungi and, apart from seeds of some fruiting plants and grass tussocks, only finely ground material is ingested (in Powlesland et al. 2006). The blunt, strong bill, with transverse ridges on the underside of the upper mandible, and the short, thick tongue are adapted for cutting, crushing and grinding to extract juices from fibrous plant material (Kirk et al. 1993). A less musculature gizzard suggests that vigorous chewing is needed to break down coarse plant material into small fragments suitable for ingestion. Much fibrous material is ejected in the form of characteristic kidney-shaped, tightly compressed pellets known as ‘chews’, and these may stay attached to the plant or more usually
litter the ground underneath, where they may remain intact for long periods, in due course becoming bleached by the sun to become telltale signs of the presence or former presence of the birds. Similarly, recent grubbings in the soil for roots and rhizomes can be identified by bill impressions and the remnant fragments of material that have been crushed, presumably to squeeze out the starchy contents. The bill is used also to strip away bark of trees and shrubs to gain access to the cambium layer and sap. The feet are used to hold food items but rarely to lift items to the bill. Blades of grass are eaten from the tip downwards, but tillers of snow tussock Chionochloa rigida and coarse leafy sedges are bitten from the plants and the bases eaten. Seeds of grasses are obtained by passing the stem through the partly opened bill. Berries, fruits and most seeds are pulped in the bill, but some hard seeds are swallowed intact (Powlesland et al. 2006).
Between June 1977 and April 1980, Best examined signs left by the parrots on Stewart Island and determined that favoured food plants were the club mosses Lycopodiella ramulosa and Lycopodium fastigiatum, narrow club fern Schizaea fistulosa, soft water fern Blechnum minus and mountain kiokio B. procerum, mingimingi Cyathodes juniperiana, inaka Dracophyllum longifolium, leatherwood Olearia colensoi, veined sun orchid Thelymitra venosa, the sedge Oreobolus strictus, saw sedge Gahnia procera and tall sedge Carex appressa. Although feeding occurred frequently throughout the year at all identified food plants, except Oreobolus strictus and Gahnia procera, variation in the utilisation of different parts of the plants occurred both seasonally and annually. Analyses of plant remains present in 648 faecal droppings collected on Stewart and Codfish Islands, between 1977 and 1998, revealed that females were more likely
to have eaten podocarp fruits or leaves of trees and shrubs, while males favoured fern and Lycopodium rhizomes, monocots in breeding years, and fruits of manuka Leptospermum scoparium in non-breeding years (Wilson et al. 2006). Podocarp fruits were much more prevalent in the diet in breeding years than in non-breeding years, and when podocarp fruits were available in breeding years the birds were less likely to eat several other foods. Fronds of Blechnum ferns appeared more frequently in the droppings of females in breeding years than in non-breeding years. As amounts of podocarp fruits increased in the diets of both sexes during the summers of breeding years, the incidence
of many other foods declined. Quantities of leaves of Hall’s totara Podocarpus hallii in the diet of females increased during summer in non breeding years, but is decreased breeding years It is suspected that these findings probably reflect differences in foraging behaviour between the sexes, particularly in breeding years, when females gather food for their nestlings mainly in forest habitats, while males feed mainly in tussock and subalpine scrub in the vicinity of their track-and-bowl systems (in Powlesland et al. 2006).
There is strong evidence that irregular breeding by Kakapo is in synchrony with the heavy fruiting of favoured food plants,
including rimu Dacrydium cupressinum and pink pine Halocarpus biformis. On Codfish Island, nesting has occurred only when more than 10 per cent of rimu branch tips bore green fruits in October (Harper et al. 2006). On the island, in the breeding season of 2002, chicks were fed almost exclusively on entire rimu fruits,each of which weighs approximately 0.1 grams, and in early April one female fed 90 grams of food to each of her two six-weeksold nestlings, so she must have eaten about 16 fruits per minute during the 113 minutes spent feeding before coming to the nest (Cottam et al. 2006). On Stewart Island, in 1981, a female rearing two nestlings fed heavily on ripe rimu fruits (Powlesland et al. 1992). On Maud Island, in 1998, the diet of three chicks in a nest in a plantation of Monterey pine Pinus radiata comprised a high proportion of pine needles in addition to food supplements, and supplementary foods were present with Blechnum fern fronds and seeds of kauri Agathis australis in the diet of nestlings on Little Barrier Island in 1990–1991 (in Powlesland et al. 2006). In 1989, a program of supplementary feeding was introduced in the hope that it would increase the low rate of reproduction, and high-protein foods were chosen because it was found that podocarp fruits contain twice the level of protein present in other foods (Rubenheimer and Simpson 2006). Although supplementary feeding arguably has had a positive impact on reproduction, the desired increases have not been achieved, and it has been suggested that calcium may be a limiting factor and foods with low macronutrient-calcium ratios may be more effective.
BREEDING Courtship behaviour of the male is a lek display involving social displaying and ‘booming’ from excavated bowllike depressions or ‘courts’ on an arena or traditional display ground (Merton et al. 1984). This highly specialised form of courtship behaviour has not been reported in any other parrot, in any other New Zealand bird, or in any other flightless bird. Each male typically has four to 12 bowls or ‘courts’, which invariably are against some form of reflecting surface, which must aid in projection of the booming call, enabling it to be heard up to 4 km away. Bowls are excavated and meticulously maintained by the male exclusively for courtship purposes. All bowls used by one male are linked by well formed tracks that are pruned of vegetation and may be spaced for 60 m or more along the crest of a ridge, or they may occupy an area only 10–15 m in diameter on a hilltop. A track-and-bowl system may be within the core
home range of a male, but more often is located up to several kilometres away. At least one bowl in each system usually is at a commanding position, such as on a ridge crest overlooking a valley. Distances between systems of neighbouring males may vary from 15 m to several hundred metres, with groups of up to 50 systems extending over several km². Each male occupies and defends his system from one breeding season to the next. ‘Booming’ always is carried out in, or very near to a bowl, and is a long-distance communication to attract females. The intensity and duration of ‘booming’ is influenced by social stimulation and light intensity, with an apparently sole survivor at one locality heard calling for an average 5 hours 35 minutes on clear nights, whereas calling by a group of males at another locality averaged
9 hours on clear nights, up to 12 hours 40 minutes on overcast nights, and under extreme conditions continued for up to 17 successive hours. ‘Booming’ usually commences about an hour after nightfall and ceases about an hour before sunrise. Neighbouring males frequently duet, but it is not known whether this is by chance or is deliberate. ‘Booming’ undoubtedly serves to advertise the location of the calling male, and possibly stimulates and synchronises sexual activity in both sexes. In years when nesting occurs, males typical ‘boom’ nightly between late November and early April, but in years when there is no nesting ‘booming’ seldom lasts more than two or three months, mostly in January–February.
Nesting occurs in synchrony with abundant fruiting or seeding of preferred food plants, mostly podocarps, at intervals of two to seven years, and it was recorded in 12 of the 29 years between 1977, when female Kakapo were rediscovered on Stewart Island, and 2006 (Powlesland et al. 2006). Mating has occurred only in years when more than 90 per cent of males attended trackand- bowl systems, or males commenced ‘booming’ before 5 December (Eason et al. 2006). On Codfish Island, it is a profuse fruiting of rimu Dacrydium cupressinum that triggers nesting, and it is likely that females become sexually active when they commence feeding on green fruits in late October and early November, with mating and egg-laying taking place in January and February (Harper et al. 2006). Because it has not been practical to collect and store sufficient green rimu fruit, an attempt to induce nesting was made in a year of poor fruiting by feeding freeze-dried fruits of rimu and kahikatea Dacrycarpus dacrydioides to females, but nesting did not take place, and in another year nesting did take place when females were fed a supplementary diet of pine cones and green walnut, but this was not a conclusive result as there was also a moderate crop of rimu fruit at the same time. No nesting was recorded on Little Barrier Island in the seven years before supplementary feeding commenced in 1989, but subsequently was recorded in five of the next eight years and, although no information on the size of fruit crops on the island in those years is available, several potential food plants, including kauri Agathis australis and Nothofagus trees, are known to have produced above-average fruit or seed crops elsewhere in New Zealand during these same five years (in Harper et al. 2006). Mating occurs mainly between early January and early March, and on Codfish Island the peak period of mating was between 15 January and 4 February. Lengthy periods of nocturnal observations at track-and-bowl systems on Stewart Island revealed that visits by females are brief, infrequent and asynchronous between individuals (Merton et al. 1984). In response to the presence of females, males at their track-and-bowl systems in Fiordland indulged in elaborate, ritualised displays and posturing, which included side-to-side rocking movements, and highlighting the exquisitely marked upperparts by walking backwards with the head slightly bowed and with vigorous flapping of the opened wings. Females may spend just a few hours in an arena and mate with only one male, or stay for up to five nights and mate with two or more males. There is no pair formation, and females leave to undertake all nesting activities without any participation by males.
All of the 67 nests found between 1980 and 2005 have been within or near to the home range of the nesting female,
with 57 being in forest and 10 in open scrubland or tussock grasslands (Powlesland et al. 2006). On Stewart Island, where
open scrubland and tussock grasslands are more common, three of the five nests were in this habitat, but on offshore islands this habitat is poorly represented, and all but seven of the 62 nests were in forest. Nests are in natural cavities at or below ground level and, of the 67 nests, 40 were in caves or burrows, 18 in standing tree-stumps, five under tussocks or other dense groundcover vegetation, and four in fallen tree-trunks. Nesting cavities averaged 500 mm in diameter, with a range of about 400 mm to more than 2 m, and heights averaged about 450 mm,with a range of 350 mm to more than 1 m. Each nest comprised a shallow bowl-shaped depression some 250–300 mm in diameter and 20-50 mm deep. Distances from the cavity entrance to the nest averaged about 500 mm, with a range of about 200 mm to more than 4 m. The nest is lined to a depth of about 50 mm with material gathered by the female on site, often from walls and ceiling of the cavity, and usually consists of dry rotted wood chips, bark, peat and soil. There are three instances of nests being
reused by the same female. Egg-laying takes place in January–February, or occasionally in March. Up to 2005, the median date of egg-laying on Little Barrier Island was 24 January, and on Codfish and Pearl Islands combined was 7 February (Eason et al. 2006). Clutches normally comprise two to four, or rarely only one or up to five eggs, with
the first egg usually being laid about 10 days after mating, and then eggs are laid at intervals of about three days. Of 67 clutches found between 1981 and 2005, nine were single-egg clutches, 19 comprised two eggs, 36 comprised three eggs, and three comprised four eggs. Females that lay early in the breeding season are capable of laying a replacement clutch if the first clutch is lost or is removed for artificial incubation. Incubation averages 30 days in duration and commences with laying of the first egg, though initially the female sits intermittently. On Stewart Island, the behaviour of an incubating female was monitored by radio-tracking, and each night she left to feed, on 11 occasions leaving 1–2 hours after sunset and on three occasions at about midnight, with her time away from the nest averaging 108 minutes (Powlesland et al. 1992). On Codfish Island, the behaviour of incubating females was monitored by remote infrared video systems, and prior to completion of the clutch females usually left the nest nightly, often for up to three hours at a time. Subsequently, they usually were away from the nest for less than 90 minutes on any night until hatching. During the first 10 to 14 nights they normally left the nest every second or third night to feed, but during the next two weeks feeding absences usually occurred nightly. When food was not readily available during the first two weeks, females left their nests every night, occasionally leaving before nightfall and not returning until after sunrise. In 1997, on Codfish Island, the behaviour of females with access to supplementary food was compared with the behaviour of females without access, and it was found that females with access to supplementary food were absent from their nests about onethird of the duration of females that relied on natural foods (in Powlesland et al. 2006).
Hatching occurs during late February to early April, and generally is at intervals corresponding to intervals of egg-laying,
though occasionally eggs laid at intervals of three days will hatch at intervals of one or two days. At hatching, chicks are blind, helpless and weigh about 28 to 35 grams (Farrimond et al. 2006a). Growth and weight gain is rapid during the first three to eight weeks, after which weight continues to increase at a more modest rate until reaching a maximum just prior to fledging when their weights mostly declined (Eason et al. 2006). From the night they hatch, nestlings are left unattended for several hours each night while the female feeds. On Stewart Island, three to five weeks old nestlings in two nests received little brooding each night, and were fed nightly at about 2300 hours and again at 0200 hours, each feeding visit by the female lasting 10 to 40 minutes. Females returned to these nests at dawn, again fed the chicks, and then brooded throughout the day (Powlesland et al. 1992). At eight to 10 weeks after hatching, daytime brooding ceased, with the females roosting away from the nests and feeding visits of 10 to 20 minutes duration by the females took place once or twice during the night and again at dawn. Fledging occurs in late May to early June, and is at an average of 76 days after
hatching, though it is a gradual process and from about nine weeks of age chicks may spend progressively longer periods a few metres away from the nest until finally not returning. On Codfish Island, the average weight of chicks at fledging was 1813 grams, with males averaging 1984 grams and females averaging 1715 grams (Farrimond et al. 2006a). When 11 or 12 weeks old, most fledglings roost on the ground more than 10 m away from the nest, and a month later they usually are roosting up to 100 m away from the nest. Young birds continue to receive some food from their mother for at least three months after leaving the nest, and they remain within or near to her home range until six to eight months of age, often roosting in close association with her. Efforts to boost numbers of Kakapo are hindered by the low rate of nesting success. Of 166 eggs monitored during 1981 to 2005, 66 were infertile, 68 hatched, and 48 nestlings fledged, with all but one of these fledglings reaching independence (in Powlesland et al. 2006). It is suggested that the high level of infertility is likely to be a result of very low genetic diversity in the surviving population. Most of the 47 chicks that reached independence would not have survived without human intervention, with 17 being partially or entirely handraised, and at least 16 of the remainder receiving supplementary food from their mothers. Survival following independence is high, with the annual survival of juveniles in the managed population at 2005 estimated to be 0.91 (Elliott 2006). The age at which Kakapo
reach sexual maturity is not known, but on Little Barrier Island fiveyears old males had established track-and-bowl systems, and their ‘booming’ was similar to that of older males. Three known-age females bred for the first time at 10 and 11 years but, as abundant fruit crops did not occur in preceding years, it is possible that they may have been sexually mature at an earlier age. It is suspected that males may reach sexual maturity at about five years of age, and females at about nine years of age. Kakapo are thought to be exceedingly long-lived. The oldest known bird, an adult male captured in Fiordland in 1975, died in December 2010, and Clout (2006) speculated that he may have been almost 100 years old.
EGGS Merton (1985) describes the eggs as being ovate and with a fine granular surface. Measurements of 122 eggs laid on offshore islands between 1990 and 2002 are 50.7 (46.3–55.8) × 38.3 (35.0–41.1) mm (Eason et al. 2006).