Rarotonga Monarch Pomarea dimidiata Scientific name definitions

14–15 cm; 22 g. Plumage is dark slate-grey  above, with whitish lores, white below  ; tail blackish, with greyish underside; iris dark; bill plumbeous blue, legs dark plumbeous. Juvenile plumage very different: rufous all over  , paler below  , with broad dark tail tip, and dark centres to all wing feathers. Previously thought that rufous plumage corresponded to females (1 Robertson, H.A., Hay, J.R. and Saul, E.K. (1993). Age and sex determination of Kakerori Pomarea dimidiata. Notornis. 40: 179–187. Close ). Immature plumages develop over four years: first-year plumage orange, with paler belly, darker wings, yellow base of lower mandible; second-year similar but with bill all steel-blue (appears black in the field); third-year variable, mixed grey and orange, or grey plumage, with black bill; fourth-year all grey with black bill. Female has shorter bill than male, usually <13·5 mm (2 Zhao, Y., Kong, X., Robertson, H.A., Saul, E.K., Nia, L.V., Chan, C.-H. and Chambers, G.K. (2009). Combining morphometric and molecular approaches improves accuracy of sexing in the kakerori (Pomarea dimidiata) on Rarotonga, Cook Islands. Notornis. 56(1): 49–53. Close ).

Introduced on Atiu I (200 km NE of Rarotonga).

Rarotonga, in Cook Is.

Undergrowth of native forest. Prefers small, steep-sided, wet, forested valleys sheltered from the SE winds in the Takitumu Conservation Area, usually at 100–250 m.

Sedentary; immatures may gather in small loose flocks on ridgetops away from occupied territories.

Feeds mainly on small caterpillars, flies (Diptera), beetles (Coleoptera) and bugs (Hemiptera). Gleans from leaves and twigs; can be bold and noisy.

Raucous  , chattering  , rapid, rasping and discordant rather metallic 4-syllable “ter whik whik whik” or “rick-rick-ree-dee’, a squeaky “ter-wickee-der”, and a quick “chep-ur-weo” or “chee-chee-dur”. Male’s loud territorial call given repeatedly during pre-breeding period, onomatopoeically rendered as “kakerori” (the species’ Maori name).

Breeds Oct–Feb, but most eggs laid Oct and early Nov. Some immatures join adults as helpers to defend territory and help to raise young. At least two adults, presumably males, seen to fly from canopy to 10 m high and perform flight with slow wingbeats, lasting c. 1–2 minutes, this regularly repeated. Bulky nest  , often placed on forked branch overhanging creek. Clutch 1 or 2 eggs, replacement laid if first clutch fails; incubation starts with first egg, and in 2-egg clutches second hatchling is smaller, weaker and less likely to survive; no information on incubation and nestling periods. Life expectancy (following conservation efforts) recorded as 15·1–18·1 years for males and 12·7 years for females.

VULNERABLE. Restricted-range species: present in Southern Cook Islands EBA. Once among the rarest birds of the world, this species has been brought back from the brink of extinction. Thought to be extinct in early 1900s, but in a 1983 survey 21 individuals and two nests recorded. Recovery plan implemented in 1987, with support of local landowners in Takitumu Conservation Area (155 ha), which has led to better breeding success and decreased adult mortality; minimum of 63 fledglings recorded in 2002/03, with some small valleys recolonized, and 2003 population numbered 290 individuals. Fears of cyclone devastation led to translocation of ten birds to island of Atiu in 2001 as a back-up population; additional releases made in 2002 and again in 2003, and the first three Atiu fledglings were recorded in Jan 2003 (4 Robertson, H.A., Karika, I. and Saul, E.K. (2006). Translocation of Rarotonga Monarchs Pomarea dimidiata within the southern Cook Islands. Bird Conservation International. 16(3): 197-215. Close ). In Feb 2005, series of five severe cyclones passed through Cook Is, and both Rarotonga and Atiu were badly affected; many monarchs survived, however, with estimate of 280 in early 2006. By 2007, population had increased to 314 birds (271 on Rarotonga and 43 on Atiu), and by Aug 2011, population estimated at c. 380 birds, suggesting a population of c. 310 mature individuals BirdLife International (2015) Species factsheet: Pomarea dimidiata. Downloaded from http://www.birdlife.org on 20/05/2015. . Since 2000, it has been successively downlisted from Critically Endangered to Vulnerable because population has increased in recent years owing to intensive conservation efforts, with no evidence of a continuing decline for the last five years BirdLife International (2015) Species factsheet: Pomarea dimidiata. Downloaded from http://www.birdlife.org on 20/05/2015. . Nevertheless, it remains conservation dependent. The species’ very small total population and tiny global range make it very vulnerable to cyclones, invasive non-native plants, and forest degradation and clearance. Introduced black rats (Rattus rattus) a major threat, and these are heavily controlled during the species’ breeding season, leading to population rises and some hope for the recovery of the other threatened members of genus. There are fears that other predators, such as snakes and mongooses (Herpestinae), or avian diseases may be introduced. Possibly suffers some predation by Long-tailed Koel (Urodynamis taitensis), a non-breeding visitor from New Zealand. Despite passing through a bottleneck of 29 birds, effects of inbreeding and loss of genetic diversity are not thought to be a threat (5 Chan, C.H., Robertson, H.A., Saul, E.K., Nia, L.V., Luong, V.P., Kong, X., Zhao, Y. and Chambers, G.K. (2011). Genetic variation in the kakerori (Pomarea dimidiata), an endangered endemic bird successfully recovering in the Cook Islands. Conservation Genetics.  12(2): 441-447. Close ). Local landowners are committed to the conservation programme  and are developing an ecologically and commercially sustainable ecotourism venture.