Data Zone
Justification of Red List category
This species has a very restricted range where habitat degradation is ongoing. It is therefore assessed as Near Threatened.
Population justification
The population was estimated at 2,350 mature individuals in 2010 (based on distance sampling in nine inland valleys, density averaging at 0.5 per hectare), and it is reported to be relatively localised and not evenly distributed (Easby 2011, Easby and Compton 2013, Thibault and Cibois 2017).
Trend justification
The population trend has not been assessed directly. The species seems to have declined in the lowlands in the 1970s possibly owing to aggressive competition from the introduced Common Myna Acridotheres tristis, however this is not currently considered to be a serious threat (Thibault and Cibois 2017). The species remains abundant in suitable habitat and there is no evidence for substantial declines (Easby and Compton 2013, Thibault and Cibois 2017, G. McCormack in litt. 2023). As such, the species is tentatively suspected to be stable overall, but up-to-date surveys are urgently required.
This species occurs in the rugged interior of Rarotonga, Cook Islands.
This is a shy and inconspicuous inhabitant of undisturbed, native montane forest and fringing disturbed forest (Pratt et al. 1987) from 150-200 m up to the highest areas of the island at 600 m (Holyoak and Thibault 1984). Although a recent survey indicated that they also frequent areas as low as 30 m (A. Tiraa in litt. 2003) they no longer seem to frequent coastal areas as much as they did in the past (A. Tiraa in litt. 2003). It is found either alone or in pairs, foraging in the canopy (Pratt et al. 1987) and appears to have a varied diet, feeding on nectar, fruit and insects (Holyoak and Thibault 1984). A nest has been observed in the cavity of an old tree (Holyoak and Thibault 1984), and birds seem to prefer to nest in native trees such as koka Bischofia javanica, mato Homalium acuminatum and turina Hernandia moerenhoutiana (A. Tiraa in litt. 2007). Surveys have reported that valleys of low starling abundance have high proportions of hibiscus Hibiscus tiliaceus and lack suitable vegetation for food and nesting, such as the Rarotonga fitchia Fitchia speciosa and Polynesian chestnut Inocarpus fagifer (Easby 2011, Easby and Compton 2013). This species lays more than one egg per clutch, uses the same nest in subsequent years, breeds between August and December and holds territories (A. Tiraa in litt. 2003).
Previously found throughout Rarotonga, but lower altitude areas have largely been converted to agriculture, human habitation or scrub (Easby and Compton 2013). The introduced Common Myna Acridotheres tristis is aggressive and widespread and is often blamed for the demise of the native landbirds (McCormack 1997). It may be implicated in the loss of this species from the lowlands, but it is not thought to have penetrated the forested uplands (A. Tiraa in litt. 2003, G. McCormack in litt 2007) and is not currently considered a serious threat (Thibault and Cibois 2017). Black Rats Rattus rattus may reduce nesting success or take incubating birds in the uplands, although overall their effect is likely to be negligible (G. McCormack in litt 2023). However, densities are highest where rats are controlled (Easby and Compton 2013, Thibault and Cibois 2017). Introduced plant species are increasingly widespread and threaten the remaining areas of native forest favoured by this species, with abundance higher where native forest is less disturbed (Easby and Compton 2013, Thibault and Cibois 2017). The introduction of exotic avian diseases, to which local birds have no immunity, is a possible threat (McCormack 1997). Other Aplonis spp. have become extinct or exceedingly rare for unknown reasons (G. Dutson in litt. 2007) and so monitoring of the species is required. Cyclones are a plausible future threat that could detrimentally affect the species (H. Robertson in litt. 2023), though the species is relatively secure in upland habitat and has persisted in spite of cyclones historically.
Conservation Actions Underway
The species presumably benefits from conservation measures carried out for the Rarotonga Flycatcher Pomarea dimidiata in the south-east of the island, including intensive rat control.
20 cm. Medium-sized, grey-brown starling. Brownish-grey head with slight purplish gloss. Pale undertail-coverts and vent. Dark brown wings and tail. Black bill and legs. Dark iris. Voice Whistles, squeaks, and bell-like notes.
Text account compilers
Vine, J.
Contributors
Dutson, G., McCormack, G., Tiraa, A. & Robertson, H.A.
Recommended citation
BirdLife International (2024) Species factsheet: Rarotonga Starling Aplonis cinerascens. Downloaded from
https://datazone.birdlife.org/species/factsheet/rarotonga-starling-aplonis-cinerascens on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.