Justification of Red List Category
This species only survives as a very small population on three offshore islands. With the instigation of intensive management in 1995, numbers are now increasing, but this species has a long generation length and the species underwent a severe population reduction over the last three generations; it therefore qualifies as Critically Endangered.
In 2017 there were 154 individuals, including 116 adults (Department of Conservation 2017). In 2018, following several deaths, there were 149 individuals remaining (Department of Conservation 2018).
The species was described as still abundant in Fiordland and some other parts of South Island in the early twentieth century. The current population comprises 149 individuals (Department of Conservation 2018), but although the population is now increasing, it has declined by >80% in the last 100 years (P. Jansen in litt. 2004, D. Merton in litt. 2005, Merton 2009) and is likely to have declined by >80% in the last three generation lengths (81 years).
This species formerly occurred throughout most of the North, South and Stewart Islands, New Zealand. Although it disappeared from most of its original range in the wake of human colonisation, the species remained abundant in Fiordland and some other higher-rainfall and more sparsely inhabited parts of South Island until the early twentieth century (Clout and Merton 1998). By 1976, however, the known population had been reduced to 18 birds, all males, all in Fiordland. In 1977, a rapidly declining population of c. 150 birds was discovered on Stewart Island. Between 1980 and 1992, 61 remaining Stewart Island birds were transferred to offshore islands (Merton 1998, Merton and Clout 1998, Higgins 1999, Merton et al. 1999), and are presently located on Codfish Island/Whenua Hou, Anchor Island, and Little Barrier Island/Hauturu-o-Toi (A. Digby in litt. 2016). The last accepted North Island record was in 1927, the last South Island record of three males in Fiordland in 1987, and the last Stewart Island record of a female found and transferred to Codfish Island in 1997 (Powlesland et al. 2006). The species is now likely to be extinct in its natural range. In 1999, only 26 females and 36 males survived (Merton and Clout 1999), comprising 50 individuals of breeding age, six subadults and six juveniles. The population stabilised, and has begun to slowly increase (Higgins 1999, Merton et al. 1999, P. Jansen in litt. 1999) following the implementation of intensive management (Higgins 1999, Merton and Clout 1999, Merton et al. 1999, Elliott et al. 2001, Clout 2006). By 2005, the kakapo population stood at 86; a productive breeding year in 2009 saw the total population increase to 124 birds (Merton 2009), and there were known to be 126 birds in early 2012. A large breeding season in 2016 increased the population to 157 (50 adult females, 58 adult males, 15 juveniles, 34 chicks; A Digby, in litt. 2016), in 2017 the population stood at 154, including 116 adults (Department of Conservation 2017), and following several deaths, the population in April 2018 stood at 149 (Department of Conservation 2018).
This large, flightless, nocturnal parrot feeds on leaves, stems, roots, fruit, nectar and seeds, and, prior to human colonisation, it formerly inhabited a range of vegetation types throughout most of the North, South and Stewart Islands. A model of kakapo fossil records and habitat types has indicated that the species previously occurred in mountain beech and Hall's totara or broadleaf forests with moderate to high precipitation and milder winters (Lentini et al. 2018). It breeds once every two to five years, coinciding with periodic superabundant seeding or fruiting periods of key podocarp plant species: on Codfish, Stewart and Pearl Islands nesting has only occurred when rimu Dacrydium cupressinum or pink pine Halocarpus biformis fruit has been abundant (Harper et al. 2006). Males cluster in traditional lekking sites and advertise their presence by calling each night for about three months, with mating occurring mainly between January and early March (Powlesland et al. 2006). One to four eggs are laid and all parental care is performed by the female, with eggs and chicks being left unattended for several hours at night. Female kakapo take 5-11 years to reach breeding age, have a mean lifespan of at least 60 years (A. Digby in litt. 2016). One productive male and female are at least 30 years old, and probably much older. Adult survivorship is now more than 98% per year (Lloyd and Powlesland 1994, Cresswell 1996, Clout and Merton 1998, Merton and Clout 1998, 1999, Higgins 1999, Merton et al. 1999, A. Digby in litt. 2016).
On Stewart Island, over 50% of monitored adults were killed each year by cats (Clout and Merton 1998). Introduced stoats Mustela erminea and black rats Rattus rattus contributed to the decline and Polynesian rats Rattus exulans can pose a threat to eggs and chicks (Collar and Sharpe 2014). Abnormally low egg fertility and exceedingly low natural reproductive and recruitment rates are major concerns. In 2004, three juveniles died of septicaemia caused by the bacteria Erysipelothrix rhusiopathiae (erysipelas), a disease which had not previously been reported in the species (P. Jansen in litt. 2004). Since 2002 at least 15 kakapo have been diagnosed with cloacitis on Whenua Hou/Codfish Island; a condition which is causing increasing concern (Jakob-Hoff 2009, White et al. 2015).
Conservation and Research Actions Underway
Kakapo are legally protected in New Zealand and listed on CITES Appendix I. Extensive research is on-going. All individuals are radio-tagged, and tracked throughout the year. Supplementary feeding has increased the success of breeding attempts, and it is hoped may be able to be used to trigger breeding in future (Higgins 1999, Raubenheimer and Simpson 2006). Reducing supplementary feeding levels has been shown to increase the percentage of female chicks produced and may assist in redressing the skewed gender balance (Clout et al. 2002, Robertson et al. 2006). A research programme is under way to assess whether low levels of vitamin D found in kakapo are natural, or as a result of management (von Hurst et al. 2016) and an analysis of vitamin D levels in kakapo in Whenua Hou found higher levels in birds that had received supplementary food (Chatterton et al. 2017). Research is also underway into the link between mast fruiting events and kakapo fertility (Stone et al. 2017, Davis ei al. 2018).
During breeding seasons, each nest is monitored using infra-red video cameras and remote proximity sensors. Methods of hand-rearing chicks are being refined. Genetic diversity of the remaining population is managed to improve hatching rates (Merton 2006). In 2015 a project was started to sequence the genomes of every living kakapo; by 2017, genomes for 82 individuals had been sequenced (A. Digby in litt. 2016, Department of Conservation 2017).
Invasive species (stoats, possums, rats, cats) have been eradicated from all islands where kakapo are now present. Translocations have been carried out to take advantage of locally abundant food supplies and increase the frequency of breeding attempts (Merton 2006). Trials of artificial insemination methods have taken place (A. Digby in litt. 2016), and in 2009 three chicks were produced using this technique (R. J. Moorhouse in litt. 2012). In 2016, successful breeding took place on Anchor Island for the first time, with a total of 34 chicks (12 hand-raised) produced from Whenua Hou/Codfish Island and Anchor (A. Digby in litt. 2016). A search for any remaining birds in Fiordland was completed in 2006, with no birds found and no evidence of their continued existence. Modelling of suitable habitat has identified sites for potential future reintroductions on the mainland (Lentini et al. 2018). A Kakapo Recovery Plan (the third since 1989), produced in partnership between the Department of Conservation, Forest & Bird and Rio Tinto Alcan (formerly Comalco), covered the period 2006-2016.
58-64 cm. Flightless, nocturnal, lek-breeding, green parrot. Moss-green upperparts. Greenish-yellow underparts. Brown-and-yellow mottling of feathers. Owl-like facial disk. Male has broader head, larger bill. Weighs up to 4 kg. Female c.65% male weight. Voice Males 'boom' repetitively at night to attract females, often audible for up to 5 km, for three to five months in some years.
Text account compilers
Ashpole, J, Stringer, C., Wheatley, H., Bird, J., Butchart, S., Calvert, R., Benstead, P., McClellan, R., Symes, A., Taylor, J., Temple, H.
Digby, A., Moorhouse, R., Merton, D., Jansen, P.
BirdLife International (2021) Species factsheet: Strigops habroptila. Downloaded from http://www.birdlife.org on 22/09/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/09/2021.