Justification of Red List Category
This species is listed as Critically Endangered because, subsequent to serious declines since the 1800s, it underwent a population crash following rat invasions in 1990-2000, and it now has a very small population that has continued to decline during the last decade.
Although the population numbered several hundreds prior to 2000, a prolific increase in the population of rats and stoats within its restricted South Island range induced a rapid population decline and the total population has remained well below its previous levels. Successful translocations on four islands have boosted the population of this species, but decreases may have continued on the mainland. Overall, the global population was estimated at 290-690 individuals in early 2013, with the mainland populations estimated to total 130-270 individuals and the island populations totaling 160-420 individuals (J. C. Kearvell in litt. 2013). Obtaining accurate population estimates is extremely challenging for the species, but recent counts indicate that the mainland population may have declined to around 100 birds, and the offshore island populations to around 250 birds in total (J.C. Kearvell in litt. 2016). The population has a skewed sex ratio of males to females, probably due to higher predation on incubating females (Kearvell and Farley 2016).
The population fell from 500-700 birds prior to 2000, to 100-200 by 2004. Increased conservation efforts (especially predator control) in its small South Island range and a successful translocation of birds to four islands suggest its rapid decline has ceased and some recovery has taken place. However, 2013 estimates suggest further declines on the mainland, and during a three generation (14 year) period the species has still experienced a reduction in the number of mature individuals. This reduction is precautionarily estimated to have been extremely rapid, as latest population estimates include an unknown but potentially significant proportion of non-mature individuals. Overall, the population appears to stabilize at low levels, and it is likely that the mainland populations remains at an extremely low level of around 100 birds in total (J. Kearvell in litt. 2016).
Formerly occurring throughout New Zealand, the species is now known from only three beech (Nothofagus spp.) forest valleys in the South Island: the Hawdon and Poulter valleys in Arthur’s Pass National Park and the South Branch of the Hurunui valley in Lake Sumner Forest Park. They are patchily distributed within these valleys; absent in many parts but in some places can be quite common (Kearvell 2013). In 1999-2000, the population crashed from perhaps 500-700 birds to a rough estimate of 100-200 as a result of ship rat irruptions in two successive summers (J. van Hal in litt. 2008, 2009).
Translocations to islands began in 2005, with 68 individuals now released on Maud and 61 individuals on Blumine Islands in the Marlborough Sounds, 46 individuals on Chalky Island in Fiordland, and 95 individuals on Tuhua/Mayor Island in the Bay of Plenty (J.C Kearvell in litt. 2013, A. Grant in litt. 2016). These releases all appeared highly successful at first with positive signs of breeding and population establishment - however, population growth has now slowed on all islands and the persistence of these populations appears to still be tenuous (A. Grant in litt. 2016). Releases of captive-raised birds to the South Branch of the Hurunui to augment the population in 2015 and 2016 appear to have been successful with released birds having successfully paired and 9-10 nests located in 2016 (J. Kearvell in litt. 2016, A. Grant in litt. 2016). Overall, the population appears to stabilize at low levels, and it is likely that the mainland populations remains at an extremely low level of around 100 birds in total (J. Kearvell in litt. 2016).
It is restricted to Nothofagus beech forest, although it may not have been so historically. On Maud Island it uses areas with a high canopy cover and low understory and ground cover (Ortiz-Catedral 2012). It requires mature trees with natural hollows or cavities for nesting. Monitoring has revealed that 80% of nests are in mature living trees, with the remaining 20% in dead trees (J. C. Kearvell in litt. 2012). Of those nests found in mature trees, 68% are in red beech Nothofagus fusca. Breeding is linked with the irregular seeding of Nothofagus when numbers can increase substantially, and it seems that populations may fluctuate significantly in line with breeding/seeding events (T. Greene in litt. 2016). In mast years, many pairs will lay a second clutch, and some may lay a third clutch, with breeding continuing through the austral winter. First clutches may average more than eight eggs, with second clutches averaging over seven in 2011. A study on Maud Island has shown that birds form pairs at around seven years of age, and nest in a variety of natural cavities where beech is unavailable (J. Kearvell in litt. 2011, 2012). It feeds on seeds, fruits, leaves, flowers, buds and invertebrates (Kearvell 1999, Kearvell 2013).
The impact of introduced predators, principally stoats Mustela erminea and rats Rattus spp., is likely to be the primary cause of decline (Higgins 1999), with recent population crashes being due to rat irruptions. The species's hole-nesting behaviour leads to a reduced ratio of females in the population due to predation of birds on the nest (Elliott et al. 1996). Silviculture of beech forests aims to harvest trees at an age when few will be mature enough to develop suitable cavities, so sufficient nest holes are unlikely in managed beech forest (Kearwell 2002). The species forages in low-growing shrubs and such lower forest levels have been subject to heavy browsing by cattle, deer and possums, altering the forest structure (Duncan and van Hal 2004). The population on Chalky Island may suffer competition from Yellow-crowned Parakeet C. auriceps (J. C. Kearvell in litt. 2011) and in time, this problem may affect other island populations. Population growth in island populations, especially on Maud Island, may also be limited through predation by falcons (Falconidae), and displacement of two nesting pairs by introduced Common Starlings Sturnus vulgaris has now been documented; the overall impact of this recently-identified threat is uncertain, but may be minimal (J. C. Kearvell in litt. 2012, 2013).
In 2008, it was confirmed that native Red-crowned Parakeets C. novaezelandiae on Little Barrier Island were suffering from psittacine beak and feather disease (PBFD). The virus has been sequenced and appears very similar to the strain found in Crimson Rosella Platycercus elegans, in which the disease is known to be endemic within the captive population. In 2009, some individuals of C. malherbi on Maud Island were showing some symptoms consistent with PBFD. In reaction, testing of the entire captive population has been undertaken, as well as more limited sampling of individuals in all three island populations, as well as other parrot species. Results indicate that antibodies for PBFD were detected in C. malherbi from both Maud Island and the captive-rearing unit; notably in the latter case antibodies were found in the C. novaezelandiae foster parents (J. C. Kearvell in litt. 2011), and the disease has now been found in C. auriceps in the Eglington Valley, Fiordland (J. C. Kearvell in litt. 2012, 2013). Monitoring for the disease in the captive population continues and the main captive breeding unit has now been declared disease-free (T. Greene in litt. 2016). Individuals at all three mainland sites and on Tuhua were seen to be in very poor feather condition in 2012/2013, with a major infestation of Dermanyssus mites having occurred on Tuhua. On the mainland, mites were suspected but immunosuppression may also be involved, either because of small population size and/or because of post PBFD issues (J. C. Kearvell in litt. 2013).
Conservation and Research Actions Underway
CITES Appendix II (1981). Hawdon and Poulter valleys are located within Arthur's Pass National Park and the Hurunui South Branch is in Lake Sumner Conservation Park (J. van Hal in litt. 2008, 2009). Monitoring and conservation of this species is problematic given the difficulty in separating it from C. auriceps. The Hurunui population is contained within a mainland island which aims to protect and restore two river valleys through integrated pest management, including minimising numbers of Mustela erminea and Rattus rattus. Monitoring of nests will verify whether this is allowing numbers to stabilise and expand. The Hawdon population received M. erminea control only during plague years, which occur, on average, every four years (J. C. Kearvell in litt. 1999). However, following the dramatic decline in the parakeet population after failure to effectively control predators, rat poisoning and stoat trapping are more extensive within the Hurunui mainland island (Keey 2004). All three valleys are now part of the Battle for our Birds initiative targeting rats and stoats in South Island beech forest sites. The control of M. erminea is now continuous, whereas control measures against rats are implemented when populations reach trigger points (J. C. Kearvell in litt. 2011, 2013). Every nest found is also individually protected with tin tree wraps (to prevent access by predators), ground predator traps and possum traps (J. van Hal in litt. 2008, 2009), and since 2003 only one nest out of 153 has been lost to invasive predators (J. C. Kearvell in litt. 2013).
Since 2003, the captive facility at Isaacs Construction Wildlife Centre, Peacock Springs (Christchurch), has released, in conjunction with Department of Conservation, a total of over 250 individuals (J. C. Kearvell in litt. 2012). Since 2005, individuals have been translocated to Chalky Island in Fiordland, which is free from predators (Duncan and van Hal 2004). The reintroduction of birds to Maud Island has been underway since 2007, and wild-bred birds are now nesting on the island. Translocations to Tuhua Island have been taking place since December 2009, and in early 2011 it was expected that all birds produced in the next captive breeding season would be released there to provide a sufficient founder population (J. C. Kearvell in litt. 2011). Translocations have also been carried out on Blumine Island (J. C. Kearvell in litt. 2012). A second captive-breeding group was being set up at Mount Bruce but has been discontinued due to a lack of capacity (J. C. Kearvell in litt. 2013). Another attempt to set up a second captive breeding population has been initiated with the Auckland Zoo with the hope that a 5th island population will be started on Rotoroa Island (T. Greene in litt. 2016). A study to assess the genetic diversity of the remnant mainland population, with the aim of ensuring that any new founder populations on islands are as genetically diverse as possible, has been completed (J. C. Kearvell in litt. 2013). An analysis of breeding data is also due to be started. A comprehensive testing programme for Psittacine Beak and Feather Disease (PBFD) in parrots throughout New Zealand was initiated (T. Greene in litt. 2012) and continued in 2013 (J. C. Kearvell in litt. 2013).
Conservation and Research Actions Proposed
Develop a technique to accurately monitor numbers. Continue to study the species's breeding biology and ecology. Stabilise and increase numbers in the mainland valley populations through predator control, and monitor effectiveness. Train people in the identification of the species (J. C. Kearvell in litt. 1999). Establish further populations on predator-free offshore islands and develop captive breeding programmes to assist with this. Closely monitor the threat from PBFD (J. C. Kearvell in litt. 2011). Continue research into methods of controlling introduced predators (J. C. Kearvell in litt. 2012).
23 cm. Bright blue-green parrot with diagnostic orange frontal band and orange patch on sides of rump. Also has pale lemon-yellow forecrown. Female slightly smaller with proportionally smaller bill. Similar spp. Red-crowned Parakeet C. novaezelandiae has a crimson forecrown. A clear view of the frons or rump patch is necessary in order to separate Malherbe's Parakeet and Yellow-crowned Parakeet C. auriceps; the frons and rump patch on Malherbe's Parakeet are orange whilst those of Yellow-crowned Parakeet are crimson (Higgins 1999, Kearvell et al. 2014).
Text account compilers
Symes, A., Taylor, J., Ashpole, J, Butchart, S., Benstead, P., Harding, M., Hermes, C., Khwaja, N., Bird, J., McClellan, R.
Kearvell, J., van Hal, J., Hitchmough, R., Greene, T.
BirdLife International (2021) Species factsheet: Cyanoramphus malherbi. Downloaded from http://www.birdlife.org on 02/12/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/12/2021.