Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The population is estimated to number 278 mature individuals on Rangatira Island. This constitutes a tiny proportion (much less than 5%) of the species's range, and so the total population is likely to number 5,560 mature individuals at the very least, but probably considerably more. It is precautionarily placed in the band 2,500-9,999 mature individuals. This equates to 3,750-14,999 individuals in total, rounded here to 3,500-15,000 individuals.
This population is suspected to be in decline owing to ongoing habitat destruction and the effects of introduced species (Higgins et al. 2001).
Text account compilers
Ekstrom, J., Harding, M., Wheatley, H., Butchart, S.
BirdLife International (2018) Species factsheet: Prosthemadera novaeseelandiae. Downloaded from http://www.birdlife.org on 26/09/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/09/2018.