Justification of Red List Category
This species is listed as Critically Endangered because it is believed to have a very small population, almost confined to one area in the south-east of New Caledonia. Its population is assumed to be declining because of forest degradation largely through an increase in anthropogenic fires.
Based on this home-range of 1 km2 per pair and habitat modelling suggesting 700 km2 of suitable habitat, the total population was estimated to be around 315–700 breeding pairs (Okahisa et al. 2016). However, a separate estimate for the southern subpopulation was 92 pairs within the Massif du Sud KBA (Angin 2011). There are likely additional pairs scattered to the north, especially around Mt Panié, but the total population is precautionarily assessed here as <250 mature individuals.
This species is likely to be suffering an ongoing habitat loss largely because of fires: the north-eastern ranges experienced a 30% decline in forest cover between 1989 and 2009 (Tron et al. 2013), although an analysis of satellite images measured only 0.6% loss of forest habitat across the species' range over the last three generations or 17 years (Tracewski et al. 2016).
The species is endemic to New Caledonia (to France) where it is now mainly restricted to small populations scattered throughout the south of the island plus the Mt Panié massif in the north (Baudat-Franceschi 2013, Okahisa et al. 2016). Extensive surveys in 2001-2012 found the species at 81 locations (Chartendrault and Barré 2005, 2006, Okahisa et al. 2016). The total area where the bird has been recorded was estimated at <400 km2 (Létocart 2006) but a habitat suitability model suggests that 700 km2 is suitable habitat (Okahisa et al. 2016). It appears to be localised and uncommon even in favoured areas, although c.18 pairs were known in the study area of Rivière Bleue, each occupying c. 1 km2 of forest, potentially extrapolated to 160 pairs across this protected area (Y. Létocart in litt. 1999). This estimate has been considered over-optimistic (N. Barré in litt. 1999), particularly if pairs require c. 1 km2, and may not be representative of the density elsewhere (Chartendrault and Barré 2005, 2006). Based on this home-range of 1 km2 per pair and habitat modelling suggesting 700 km2 of suitable habitat, the total population is likely to be around 315–700 breeding pairs (Okahisa et al. 2016). This is lower than Ekstrom et al. (2002)'s suggestion of approximately 1,000–3,000 individuals which was based upon the assumption that all forests on ultramafic substrates provided suitable habitat for the species. A more precautionary but empirically-based estimate is 92 pairs within the Massif du Sud KBA (Angin 2011) plus a very few additional pairs scattered to the north.
It inhabits a humid forest/maquis matrix, including small isolated forest patches, usually on ultrabasic soils, 100-850 m, historically in the hills to 1,000 m (Ekstrom et al. 2000), and has also been recorded in dry forests at Pouembout (S. Sirgouant verbally 1998, N. Barré in litt. 2003). Habitat modelling of an extensive series of recent surveys suggests that the species prefers altitudes of 600–900 m on ultramafic soil in high rainfall (>3000 mm rain per year) areas and in forest patches larger than 100 km2 and with high forest cover (Okahisa et al. 2016). It is an unobtrusive species seen singly or in pairs in the canopy or midstorey, feeding on invertebrates and nectar (Warner 1947, Ekstrom et al. 2000). Nests are built by the female alone in open forests and are very poorly camouflaged, leaving them open to predation (Létocart 2006, Cassan et al. 2017). Radio telemetry revealed that a pair occupied a territory of 100 ha (Létocart 2006). Birds appear to maintain the same territory and from year to year nests appear to be situated close together in the core of the territory. In the Parc de la Rivière Bleue the species breeds between July and December (Baudat-Franceschi 2013). The female lays only one egg per breeding season (Cassan et al. 2017).
Forest loss and degradation caused by logging, nickel mining and fires is likely to be a threat (Ekstrom et al. 2000, 2002), potentially having had a considerable impact in the côté oubliée from where the species now appears to be absent (V. Chartenrauldt in litt. 2009). The apparent decline at Rivière Bleue must be caused by other factors; with the species apparently subjected to severe predation pressure by introduced rats Rattus spp.(Ekstrom et al. 2002, N. Barré in litt. 2003, Létocart 2006) and possibly cats Felis catus (R. Stirnemann in litt. 2012). No successful nests or juvenile birds were seen until 2004 at Rivière Bleue, suggesting that the limiting factor affects its breeding success (Y. Létocart in litt. 1999). However, in 2004 and 2005, two chicks fledged successfully and were tracked visually for a few days. Nesting areas were heavily poisoned for rat population control which may explain the nesting success but another nest, found in 2005, and also in an area where rats were controlled failed with the chick disappearing during the first week (Létocart 2006). Other possible nest predators include native endemic predators such as New Caledonian Crow (Corvus moneduloides), White-bellied Goshawk (Accipiter haplochrous), New Caledonian Giant Gecko (Rhacodactylus leachianus), Swamp Harrier (Circus approximans) and Peregrine Falcon (Falco peregrinus) (Baudat-Franceschi 2013); nests are poorly camouflaged and presumably easy to locate (Létocart 2006). One of the two chicks visually monitored after fledging was usually moving between trees on the forest floor, this could mean that the species is also vulnerable to dogs and pigs (Létocart 2006). Grazing of understory vegetation by Rusa Deer (Cervus timorensis) may reduce habitat quality for the species (Baudat-Franceschi 2013). Forestry operations pose a threat as access roads allow the spread of invasive species, fire and hunters (Baudat-Franceschi 2013). Given the very small population size, hunting is also a potential threat. The species may be susceptible to avian malaria.
Conservation Actions Underway
Hunting and capture is prohibited. The main known populations are found within protected areas: Parc Provincial Rivière Bleue, Réserve naturelle du Mont Kouakoué, Réserve naturelle de la Haute Pourina and Réserve botanique du Mont Panié (Baudat-Franceschi 2013). A breeding monitoring project conducted basic ecological research in the protected Parc Provincial Rivière Bleue from 2001 to 2005, including the radio-tracking of adults and video monitoring of nests (Y. Létocart in litt. 1999, Létocart 2006). Surveys were conducted in 2003-2006 by the IAC to establish the status of forest birds across New Caledonia (Chartendrault and Barré 2005, 2006). In 2010, the SCO conducted surveys in the Massif du Sud IBA (Angin 2011). There is ongoing conservation work around Mt Panié in the north (Tron et al. 2013).
41cm. Very large, crow-like honeyeater with orange facial wattles. Plumage all glossy black, bill grey above and yellow below, legs yellow and facial skin varies from yellow to red. Long rounded wings and fairly long neck and tail. Similar spp. New Caledonian Crow Corvus moneduloides and Melanesian Cuckoo-shrike Coracina caledonica have short dark bills and no bare facial skin - crow has short tail and cuckoo-shrike has long pointed wings. Voice Loud, repeated series of slightly varied phrases, typically a loud nasal note e.g. chong, followed by a descending series, e.g. tchku-tchku-... Harsh scolding tcharr or wa-wa similar to parrot or crow. Hints Listen at dawn.
Text account compilers
Mahood, S., Stattersfield, A., Ashpole, J, Derhé, M., Benstead, P., Dutson, G., Bird, J., Ekstrom, J., Harding, M., Hermes, C.
Barré, N., Theuerkauf, J., Ekstrom, J., O'Brien, M., Chartendrault, V., Meriot, J., Dutson, G., Spaggiari, J., Létocart, Y., Stirnemann, R., Meresse, C., Sirgouant, S.
BirdLife International (2022) Species factsheet: Gymnomyza aubryana. Downloaded from http://www.birdlife.org on 23/01/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/01/2022.