The Kea (Nestor notabilis) is endemic to New Zealand, and is currently listed as Vulnerable under criterion C2a(ii) on the basis of a small and declining population size. The population is sparsely distributed across a range of approximately 3.5 million hectares in the South Island from Kahurangi to Fiordland, and including the Kaikoura Ranges. They are most common in montane forests and adjacent subalpine and alpine zones. They are absent from the Marlborough Sounds, Catlins, Blue Mountains and both the North Island and Stewart Island. Pockets of high population densities persist in some areas, such as around Arthur’s Pass and South Westland (Orr-Walker et al. 2015).
Kea mainly nest within native forest. Their foraging habitat includes all types of native forest, sub-alpine scrub, tussock and herb-field. Threats to this species include introduced mammalian predators, environmental lead, and conflict and accidents related to humans and their equipment. Episodic, high mortality events are thought to be associated with “plagues” of stoats Mustela erminea which occur after mast seeding of native beech and rimu (Kemp 2013).
Estimating Kea population size is difficult due to their extensive range over rugged terrain, their low population density, the cryptic behaviour of adults and the flocking behaviour of juveniles. A conservative estimate of one adult female per 2,000 hectares of forest gives a total population of 4,000 mature individuals in the population. Productivity estimates predict one juvenile for every breeding pair, giving a total population of about 6,000 birds (Kemp 2013).
Recent survey data indicate that Kea have undergone substantial recent population declines. For example, density in the upland beech forest of Nelson Lakes National Park in 2011 was approximately one adult female Kea per 2,750 hectares, down from about one per 550 ha in 1998 (Adams et al, 2011; Kemp 2013): this represents an 80% decline in density over 13 years or just over one generation. There are also numerous anecdotal reports of decreases from other unmanaged areas (Orr-Walker et al. 2015).
Although densities in other populations are much higher than at Nelson Lakes, it is likely that Kea in areas not subject to predator control are continuing to decline. It is not yet clear that predator control has had its desired impact of increasing populations, although it has been associated with substantial increases in nest survival and therefore in recruitment of young birds (Kemp 2013). Continued predator control is planned as part of New Zealand’s “Battle for our Birds” (DOC 2016).
Kea nests were monitored by the Department of Conservation between 2009-2014. In areas without pest control, only 2% of nests were successful. By comparison, in 2015, in areas treated with aerial 1080, 27% of nests were successful (DOC 2016). It is estimated that around 60% of Kea nests are normally attacked by predators, especially stoats, which may also kill adults; this can rise to as many as 99% of nests being attacked in a stoat “plague” (DOC 2016). Without pest control, a continued decline in Kea numbers is predicted, and the species is now considered Nationally Endangered in New Zealand, having had its status reviewed in 2012 (Robertson et al. 2013, DOC 2016).
Given the evidence of the substantial past, and continuing population declines, it is recommended that this species should be uplisted to Endangered under criteria A2be and A4be. This is on the basis that the total population decline over the last three generations (36 years) is likely to have been more than 50% but less than 80%, and that the causes of decline (predation by introduced mammals) have not ceased.
Additional information and comments on this proposal are welcomed.
Adams N.J.; Kemp, J.; Orr-Walker, T.; Roberts, L.G. 2011. Surveying the Southern Alps: Substantial differences in indices of kea (Nestor notabilis) abundance across its range may reflect response to pest management. Australasian Ornithological Conference, James Cook University, Cairns.
DOC. 2016. Battle for our Birds. Available at http://www.doc.govt.nz/our-work/battle-for-our-birds/ (accessed on 05 October 2016).
Kemp, J. 2013. Kea. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
Orr-Walker, T.; Kemp, J.; Adams, N.J.; Roberts, L.G. 2015. A Strategic Plan for Kea Conservation. Kea Conservation Trust and the Department of Conservation, New Zealand.
Robertson, H. A.; Dowding, J. E.; Elliott, G. P.; Hitchmough, R. A.; Miskelly, C. M.; O’Donnell, C. F. J.; Powlesland, R. G.; Sagar, P. M.; Scofield, R. P.; Taylor, G. A. 2013. Conservation status of New Zealand birds, 2012. NZ Threat Classification Series 4. Department of Conservation. Wellington.