Justification of Red List Category
This species may still have a small pure-bred adult population. Its possible extirpation through hybridisation has been averted owing to three decades of conservation efforts, which have seen the population size increase. It is restricted to one location (given the proximity of the tiny islands it inhabits, and its mobility), and its small population size mean that it still warrants listing under a threatened category, but its population size has likely been >250 mature individuals for over 5 years and so it has been downlisted to Vulnerable.
The population of forbesi-like phenotypes has increased dramatically on Mangere Island with best estimates placing the population at 800-1,000 individuals. A survey in 2011 assessed the phenotypes of concern to be at 10%, the trigger level for management action (D. Houston in litt. 2012). The populations has now likely exceeded 250 mature individuals for over 5 years and so it is now placed in the range of 250-999 mature individuals.
The population has shown minor fluctuations in recent years, as the species recolonised Mangere Island by the 1970s and has benefited from habitat restoration, while it has also suffered from hybridisation. Overall, the population is estimated to have been stable over the last ten years, and is probably increasing (T. Greene in litt. 2012).
Cyanoramphus forbesi is restricted to Little Mangere and Mangere Islands in the Chatham Island group, New Zealand. By 1930, it was extinct on Mangere Island, but by 1973 it had recolonised and numbered 40 birds and a small number of hybrids with C. n. chathamensis (of which there were 12 on the island) (Higgins 1999). In 1996, two estimates indicated that the population on Mangere Island numbered 50-120 pure-bred birds. The Little Mangere Island population is poorly known due to few visits taking place (H. Aikman in litt. 1999). In 1999, the total population was estimated to be about 120 birds (Aikman et al. 2001), but surveys in 2003 estimated 900 individuals on Mangere Island (Aikman and Miskelly 2004, D. Houston and C. Miskelly in litt. 2008). A recent study estimated that over 50% of the parakeet population on Mangere Island consisted of hybrid individuals (Chan et al. 2006), but this is expected to decrease owing to positive assortative mating (T. Greene in litt. 2012); the number of non-forbesi phenotypes is approaching the 10% management threshold (D. Houston in litt. 2012) (i.e. the number above which culling may be resumed as a management tool). Birds have been recorded visiting the south of Chatham Island, Pitt Island and Rangatira Island (Taylor 1998, D. Houston and C. Miskelly in litt. 2008, T. Greene in litt. 2012).
It appears to prefer dense, unbroken forest and scrub, whereas Red-crowned Parakeets Cyanoramphus novaezelandiae are more common in open habitats. It feeds on invertebrates, flowers, seeds, leaves, fruit, shoots and bark (Nixon 1994, Higgins 1999). It nests in natural crevices or hollows in dead or living trees (Higgins 1999), as well as abandoned petrel burrows and other holes in ground or under trees (T. Greene in litt. 2012).
It disappeared from Mangere Island owing to a combination of deforestation for pastoralism, decades of burning, the effects of introduced grazing mammals and predation by feral cats (Higgins 1999). The greatest present threat is hybridisation with C. n. chathamensis which, despite culling, continues to establish itself on Mangere Island (J. Kearvell in litt. 1999). The previously high rate of hybridisation is believed to be the result of the then low population sizes of the two species (D. Houston and C. Miskelly in litt. 2008). Levels of hybridisation have remained below 10% of the total Mangere Island parakeet population for the past decade, and so no management intervention has been necessary.
Conservation Actions Underway
CITES Appendix I and II. Mangere Island has been substantially re-vegetated (Aikman et al. 2001, D. Houston and C. Miskelly in litt. 2008). An ecological and genetic research programme has investigated population dynamics, hybridisation and mate selection (H. Aikman in litt. 1999, Chan et al. 2006). During 1976-1999, hybrid birds and C. n. chathamensis individuals were culled from the population (Nixon 1994). In 1998, 40 hybrids and six C. n. chathamensis were killed, leaving c.10 hybrids and C. n. chathamensis after the operation (H. Aikman in litt. 1999). Surveys of the relative proportion of hybrids to Forbes-type phenotypes are carried out biennially (D. Houston in litt. 2012). Translocation into a predator-proof fenced area on Chatham Island is planned for 2017 (D. Houston in litt. 2012).
23 cm. Bright green long-tailed parrot with crimson frontal band and bright, golden-yellow forecrown. Red patch on sides of rump. Female slightly smaller with proportionally smaller bill. Similar spp. Chatham Island Red-crowned Parakeet C. novaezelandiae chathamensis has crimson forecrown (Taylor 1998).
Text account compilers
Benstead, P., Bird, J., Khwaja, N., McClellan, R., Taylor, J. & Stringer, C.
Aikman, H., Greene, T., Houston, D., Kearvell, J. & Miskelly, C.
BirdLife International (2021) Species factsheet: Cyanoramphus forbesi. Downloaded from http://www.birdlife.org on 19/09/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/09/2021.