Archived 2011-2012 topics: Rarotonga Monarch (Pomarea dimidiata): downlist to Vulnerable?

Initial deadline for comments: 31 January 2012.

BirdLife species factsheet for Rarotonga Monarch

Rarotonga Monarch Pomarea dimidiata is endemic to Rarotonga in the Cook Islands and has been translocated to Atiu. Its preferred habitat is humid forest on valley slopes. The species is currently listed as Endangered under criterion D1 on the basis that its population was thought to number fewer than 250 mature individuals.

However, survey data indicate that the number of mature individuals (yearlings and older in this species) has exceeded 250 since 2001 (H. Robertson in litt. 2011). The observed population growth since the early 1990s, faltering only due to bad cyclones in 2005 and the poor breeding season that followed, has been achieved thanks to intensive conservation work. The latest census, in August 2011 (supplemented by data from July 2011), has estimated the current population at c.380 birds, including 69 yearlings (Robertson et al. 2011, H. Robertson in litt. 2011), suggesting a population of c.310 mature individuals.

This suggests that the species should be downlisted now that the population has included more than 250 mature individuals with no evidence of a continuing decline for at least five years. It is proposed that the species now be listed as Vulnerable under criteria D1; D2, on the basis that the increasing number of mature individuals remains below 1,000 and it is still present at only two locations and thus still susceptible to extreme weather events and other stochastic factors that could drive it to qualify as Critically Endangered or even Extinct in a short time period. Comments are invited on the proposal to downlist the species to Vulnerable and additional information would be welcomed.


Robertson, H., Adams, L. and Cockburn, S. (2011) Status of Kakerori (Pomarea dimidiata) on Rarotonga, Cook Islands, in August 2011. Report to the Takitumu Conservation Area Project, and the Te Ipukarea Society as part of the project “Sustainable management of Rarotonga Flycatcher and Its Habitat”. Wellington, New Zealand: Department of Conservation.

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3 Responses to Archived 2011-2012 topics: Rarotonga Monarch (Pomarea dimidiata): downlist to Vulnerable?

  1. Mark O'Brien says:

    This makes sense based on the fantastic effort that has been achieved to date. The only concern I have is that the, currently substantial, population on Rarotonga is only maintained as a result of annual, intensive conservation action. If this action should cease then the species is likely to move back to EN/CR very rapidly.

  2. I’m agree with Mark O’Brien, the conservation programme is very successful and the statut deserves to be downlisted. But the control area is not extensible and can not include every territory of Pomarea… I don’t know if the managers of the species are looking for a sustainable alternative for the long term. So maybe it is too early to downlist to VU because the population in maintened by human action (Pomarea genus is really sensitive to rat predation ;). Maybe wait for a more solid population on Atiu, where no actions are needed.
    And Congratulations to the team !!!

  3. I agree that the Rarotonga Monarch (Kakerori) no longer fits the criteria to be listed as Endangered because there have been over 250 mature individuals for over a decade, and a total population of around 500 birds at present, c. 380 on Rarotonga and c.120 on Atiu. Kakerori are capable of breeding at 1 year old (when they got down to 29 birds in 1989 all 5 yearlings bred), but nowadays it is rare for yearlings to breed (<5%), and most do not start breeding until 3-4 years old.

    The species is still very much conservation dependent, and the Rarotonga population remains confined to about 200 ha – birds forego breeding opportunities to remain in close contact with their conspecifics. The conservation effort is shared by a couple of very dedicated individuals, Ed Saul and Lynda Nia, and so a priority must be to broaden the base of people interested in carrying out the necessary rat poisoning programme for 3 months each year. Both Rarotonga and Atiu populations are vulnerable to a direct hit by cyclones, or to new pests or diseases introduced to the Cook Islands. Despite passing through a bottleneck of 29 birds, the genetic diversity in the species is moderately good and in line with the population being near that bottleneck size for only a short period of time. A bonus for the species was that when the population was very small an extremely high percentage of individuals bred successfully and so contributed to the extant population.

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