Data Zone
Justification of Red List category
This species has a very small population size of less than 1,000 mature individuals, is restricted to a very small area and only two locations, with the plausible threat of introduced predators that could drive the taxon to CR in a very short period of time. For these reasons it is classified as Vulnerable.
Population justification
The population of forbesi-like phenotypes has increased dramatically on Mangere Island in the past as a result of habitat management and exotic predator control. 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) following culling of Cyanoramphus novaezelandiae. Since then it has likely decreased to 600-700 mature individuals with rapid regeneration and planting of vegetation (T. Greene in litt. 2020). A survey in 2011 assessed the phenotypes of concern to be at 10%, the trigger level for management action (D. Houston in litt. 2012) but number of hybrids appear to have stabilised or declined since (T. Greene in litt. 2020). The population has exceeded 250 mature individuals for well over 5 years and is currently thought to be stable (Robertson et al. 2021), so it is placed in the range of 250-999 mature individuals.
Trend justification
Habitat management and predator control has caused the species to dramatically increase in the past, and it is now considered to be stable. The population has shown minor fluctuations due to both habitat restoration and hybridisation as the species recolonised Mangere Island by the 1970s. Overall, the population is estimated to have been stable over the last three generations (Robertson et al. 2013, 2017, 2021).
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). 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-fronted 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).
The species disappeared from Mangere Island at the beginning of the 20th century owing to a combination of deforestation for pastoralism, decades of burning, the effects of introduced grazing mammals and predation by feral cats (Higgins 1999) however since the early 1970s has recovered as a result of habitat management and exotic predator control, as well as culling of Chatham Island red-fronted parakeets Cyanoramphus novaezelandiae. The threat of introduced predators remains a plausible threat. Hybridisation with Chatham Island red-fronted parakeets is an ongoing threat to the species which, despite culling, continues to establish itself in low numbers on Mangere Island (J. Kearvell in litt. 1999; T. Greene in litt. 2020). In 2006 it was estimated that over 50% of the birds with Forbes' parakeet morphology may be hybrids (Chan et al. 2006). The previously high rate of hybridisation is believed to be the result of the previously low population sizes of the two species (D. Houston and C. Miskelly in litt. 2008), but this has greatly decreased owing to positive assortative mating (T. Greene in litt. 2012). A survey in 2011 assessed the phenotypes of concern to be at 10%, the trigger level for management action (D. Houston in litt. 2012). However, number of hybrids appear to have stabilised or declined since (T. Greene in litt. 2020). It is therefore thought that 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. Currently the population of hybrid birds is monitored, and culls will resume if the number of hybrid birds on Mangere Island reaches 10% of the total number of parakeets on the island.
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). Culling will resume if the number of hybrid birds on Mangere Island reaches 10% of the total number of parakeets on the island. Translocation into a predator-proof fenced area on Chatham Island was planned for 2017 (D. Houston in litt. 2012) but is yet to be carried out because of ongoing concerns over suitability of translocation habitats (T. Greene in litt. 2020).
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-fronted Parakeet C. novaezelandiae chathamensis has crimson forecrown (Taylor 1998).
Text account compilers
McClellan, R., Benstead, P., Taylor, J., Bird, J., Khwaja, N., Stringer, C., Vine, J.
Contributors
Aikman, H., Greene, T., Houston, D., Kearvell, J. & Miskelly, C.
Recommended citation
BirdLife International (2024) Species factsheet: Chatham Islands Parakeet Cyanoramphus forbesi. Downloaded from
https://datazone.birdlife.org/species/factsheet/chatham-islands-parakeet-cyanoramphus-forbesi on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.