NT
Rarotonga Fruit-dove Ptilinopus rarotongensis



Justification

Justification of Red List Category
This species now occurs only on two tiny islands, with the majority of the very small population occurring on Atiu. Its population size is suspected to be very small, and a stochastic event such as a severe cyclone could rapidly affect all individuals on either range island and drive the species to Endangered status. For these reason, the species qualifies as Near Threatened.

Population justification
The species is common throughout the makatea (limestone forest) and inland of Atiu (McCormack 2007). On Rarotonga, it is restricted to the inland mountains (M. O'Brien pers. comm. 2021).

The population on Rarotonga is considered likely to exceed 500 individuals, with perhaps twice that number present on Atiu (McCormack 1997, J. Pilgrim in litt. 2002, G. McCormack in litt. 2007), which implies a total population size of at least c. 1,000 mature individuals. Based on a range area of 75 km2, the first and third quartile recorded population densities of congeners (10 and 47 individuals per km2, respectively), and assuming the range to be 75-95% occupied, the population size may be suspected to fall in the range 560-3,400 individuals, roughly equating to 370-2,300 mature individuals. The population size is therefore here placed in the band 250-2,499 mature individuals, with a best estimate in the band 1,000 - 2,499 mature individuals.

There is no evidence of inter-island movements (Baptista et al. 1997), so there are assumed to be two isolated subpopulations. The largest subpopulation is found on Atiu (McCormack 1997, J. Pilgrim in litt. 2002, G. McCormack in litt. 2007).

Trend justification
In 1973, the species was common on both range islands, with an estimated Rarotonga population of 2,000 - 3,000 individuals (Holyoak and Thibault 1984). In 1987, the population on Rarotonga was estimated at fewer than 100 individuals, and the total population was estimated at 350-1,500 individuals (Pratt et al. 1987). The species is now common in the inland mountains of Rarotonga and throughout the makatea (limestone forest) and inland of Atiu (McCormack 2007), and the population on Rarotonga probably exceeds 500 individuals, and with perhaps twice that number present on Atiu (McCormack 1997, J. Pilgrim in litt. 2002, G. McCormack in litt. 2007).

There is no evidence for any population decline (G. McCormack in litt. 2007), so the species's population size is assumed to be stable.

Distribution and population

Ptilinopus rarotongensis survives only on Rarotonga and Atiu, Cook Islands, but was once more widespread given early historic records from Aitutaki and Mauke, and fossils from Mangaia (Steadman 1989).

Ecology

On Rarotonga, it is most common in hillside and upland forest, often visiting the horticultural lowland areas. On Atiu, it is found in a wide variety of wooded habitats, including the fringes of plantations as well as forest growing on the makatea (raised coral limestone), but it avoids the villages (Pratt et al. 1987, Baptista et al. 1997). It is found at all altitudes. It is an arboreal forager (Lapiedra et al. 2013), primarily frugivorous, but has also been reported to peck small insects from foliage (Baptista et al. 1997). There is no evidence of inter-island movements (Baptista et al. 1997).

Threats

There is no evidence that the black rat Rattus rattus, which is present on Rarotonga, poses any threat to this species. The introduction of exotic avian diseases to which local birds have no immunity, although unlikely, is another possible threat (McCormack 1997). Although the introduced Common Myna Acridotheres tristis is likely to reduce the nesting success of this species in horticultural and village areas it does not penetrate into heavily forested areas. Habitat destruction is likely to be a fairly minor threat at present since most native forest required for horticulture and housing was cleared a long time ago. Cyclones could threaten both supopulations and are likely to increase in frequency and/or intensity due to climate change. 

Conservation actions

Conservation Actions Underway
No conservation actions are known.

Conservation Actions Proposed
Survey and monitor the species on both islands to establish numbers and trends. Research its ecology, including foraging and dietary studies (Steadman and Freifeld 1999). Take measures to ensure that alien species are not accidentally introduced, especially R. rattus on Atiu. Consider translocation to Mangaia (Steadman and Freifeld 1999).

Identification

20 cm. Small, mostly green pigeon. Pale greenish-grey foreparts (head, chest, upper back) contrasting with remainder of plumage but with indistinct borders. Brilliant rose-lavender crown and forehead, yellow underparts, upper belly variably tinged copper-red. Bill red at base, apple-green at tip. Red-orange iris and feet. Voice Evenly spaced series of low notes HOO-HOO-hoo-hoo-hoo-hoo-hoo.

Acknowledgements

Text account compilers
Wheatley, H.

Contributors
Dutson, G., McCormack, G., Pilgrim, J., Shutes, S., Stattersfield, A., O'Brien, A., Benstead, P., Derhé, M., Mahood, S., North, A., O'Brien, M., Brusland, S. & Cibois, A.


Recommended citation
BirdLife International (2022) Species factsheet: Ptilinopus rarotongensis. Downloaded from http://www.birdlife.org on 19/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/08/2022.