Justification of Red List Category
This species was last seen in 2007, and is considered by some to be extinct. If it is still extant, it is thought to have an extremely small population, which may be declining as a result of invasive predators. Therefore, it is listed as Critically Endangered (Possibly Extinct).
The last confirmed sightings of this species were in 1967 and again 2007, with several unconfirmed sightings between 1990 and 2016 (Milne and Stocker 2014, Evans 2016, Redmond 2016). The New Zealand Department of Conservation formally declared the species to be extinct in 2007 (Brooks 2011), but reclassified it to Data Deficient in 2012 (Milne and Stocker 2014). If it persists, it is likely to have a very small population size (<50 mature individuals).
Given the ongoing threat from introduced predators a continuing decline is inferred.
This species is endemic to South Island, New Zealand. The last confirmed sightings of the species were in 2007 (Miskelly et al. 2013), and before that in 1967 (Clout and Hay 1981); it is now considered possibly extinct, with recent reports not deemed to be credible (Bain 2009, Evans 2016).
The species is assumed to have a similar ecology to the formerly conspecific North Island Kokako Callaeas wilsoni which prefers lowland, tall podocarp/hardwood forests with a high diversity of plant species, and is rarely found in modified forests, including selectively logged forests (Heather and Robertson 1997).
The historical decline was due to large-scale habitat destruction, fragmentation and the introduction of predators and competitors. Predation of eggs and chicks by black rats Rattus rattus and brush-tailed possums Trichosurus vulpecula is the main cause of nest failure, whereas deaths to nesting adult females were caused by stoats Mustela erminea (Flux et al. 2006). These introduced predators are currently the primary threat to the species. Trichosurus vulpecula also competes for many preferred food items, and introduced goats and deer destroy favoured understorey food-plants (Innes et al. 1999). Historical forest destruction for logging has also been important, especially as the species is thought to require fairly large tracts of forest. These two threats were largely contemporaneous and so their relative importance is not completely clear (Rasch 1991).
Conservation Actions Underway
Most of the remaining habitat is protected and almost all key subpopulations are managed for the control of R. rattus and T. vulpecula. Recent research shows that pulsing poison bait delivery (at least three managed years every 10) may be the most effective way of dealing with the predator threat (Bassé et al. 2003). Efforts are continuing to be made to locate individuals of this species (see, e.g. Evans 2016), and sightings continue to be claimed (e.g. Redmond 2016).
Text account compilers
Temple, H., Westrip, J., Calvert, R., Benstead, P., Hermes, C., Bird, J., Khwaja, N., McClellan, R., Stringer, C., Taylor, J.
Innes, J., Flux, I.
BirdLife International (2019) Species factsheet: Callaeas cinereus. Downloaded from http://www.birdlife.org on 19/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/08/2019.