Justification of Red List Category
This species qualifies as Vulnerable because it is suspected to be undergoing a rapid population decline as it is restricted to low-lying forest in a region where this habitat-type is being cleared and degraded at a rapid rate.
The population size is preliminarily estimated to fall into the band 10,000-19,999 individuals. This equates to 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals.
A rapid and on-going population decline is suspected to be occurring, given that this species is restricted to lowland primary rainforest - a habitat that is being cleared at an alarming rate across the entire range.
Cyornis caerulata occurs on Borneo (including Brunei, Sabah and Sarawak, Malaysia, and Kalimantan, Indonesia) and Sumatra, Indonesia, where it is resident in humid lowland evergreen forest, ascending foothills locally to mid-altitudes. It appears to be rather patchily distributed, occurring at relatively low densities and generally uncommon.
It frequents the middle and understoreys of primary, selectively logged and mature secondary dryland rainforest, tending to occur in more dense or tangled areas or at edges of clearings. Although the species has been found to tolerate selectively logged and secondary rainforest, it occurs at much lower densities in these habitats (Ansell et al. 2010, Derhé 2010, Hua et al. 2011). It is often replaced in riverine forest by Malaysian Blue-flycatcher C. turcosa.
The species has been reported to occur at lower population densities in secondary and selectively forests than in primary forests (Ansell et al. 2010, Derhé 2010, Hua et al. 2011). Given its preference for primary lowland forest and restriction to Sumatra and Borneo, it is likely to be in steep decline from habitat loss, primarily through agricultural conversion following industrial-scale logging (even in some protected areas). Kalimantan lost just under 25% of its 1985 lowland forest cover in the subsequent 12 years, resulting in the prediction that this habitat-type could be eradicated from the entire province by 2010 if changes in policy and management were not forthcoming. Rates of loss on Sumatra were even higher, with 30% of lowland forest loss in the same 12-year period. Fire is also a threat to the species's habitat, with the major fires of 1997-1998 affecting 50,000 km2 of forest on Sumatra and Borneo and damaging at least 17 of Indonesia's parks and reserves. Following previous major conflagrations in 1972 and 1982-1983, the 1997-1998 fires accelerated the desiccation of the forest environment, halting regrowth and rendering unburnt adjacent areas ever more vulnerable to fire and ever poorer in biodiversity.
Conservation Actions Underway
It occurs in various protected areas throughout its range, including Sepilok Forest Reserve (Sabah), Gunung Mulu National Park (Sarawak), Kutai National Park (Kalimantan), Kerinci-Seblat and Way Kambas National Parks (Sumatra).
14 cm. Small, brightly-coloured, forest-dwelling flycatcher. Male has dark blue upperparts, wings and tail, paler and brighter on the forehead and supercilium. Black chin, rest of underparts rusty-rufous. Female is brown above with pale eye-ring and blue rump and tail. Similar spp. Male Mangrove Blue-flycatcher C. rufigastra is similar, but lacks the contrasting pale forehead and supercilium and is duller on the lower back and rump. Female is blue above with whitish loral spot. Voice Thin three-note whistled song with last note descending, si-si-tiuuuw.
Text account compilers
Benstead, P., Derhé, M., Gilroy, J.
Brickle, N., Poulsen, M.
BirdLife International (2019) Species factsheet: Cyornis caerulatus. Downloaded from http://www.birdlife.org on 13/11/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 13/11/2019.