Current view: Data table and detailed info
Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
IUCN Red List criteria met and history
Red List criteria met
Red List history
| Migratory status |
not a migrant |
Forest dependency |
high |
| Land-mass type |
shelf island
|
Average mass |
- |
Population justification: The population size of Cyornis caerulatus is unknown. The species is considered uncommon to locally common on Borneo but appears very rare on Sumatra (BirdLife International 2001, Hua et al. 2011, Clement 2020). Most recent records of the species are clustered in the north-eastern corner of Sabah (Hua et al. 2011, eBird 2024). The species is patchily recorded throughout the rest of Borneo, which may in part reflect survey effort across the island (Hua et al. 2011), with recent records outside of Sabah from Gunung Mulu National Park and Kubah National Park in north and south-eastern Sarawak, respectively (eBird 2024). Regardless of survey effort, the species appears to occur at low densities even in undisturbed suitable habitat (Slik and van Balen 2005, Ansell et al. 2010, Hua et al. 2011), but has been recorded as locally common in central Kalimantan (Fischer et al. 2016), suggesting small pockets of high density populations may occur. On Sumatra, the species appears to have always been rare (van Marle and Voous 1988, BirdLife International 2001, Hua et al. 2011). The only Sumatran records this century are one observation from Kerinci Seblat National Park, Bengkulu (Hutchinson 2006), four individuals from Solok Selatan in west Sumatra (Kemp 2008 in Hua et al. 2011), and six individuals from Harapan Rainforest Restoration Site (Hua et al. 2011). Overall, this reflects a likely very small, localised, and patchily distributed population. However, it is not possible to estimate the total population size from current information.
Trend justification: C. caerulatus occupies lowland primary forest (Clement 2020), a habitat type that has been cleared at alarming rates both historically and contemporarily (BirdLife International 2001, FWI/GFW 2002, Sodhi et al. 2004). Forest loss within the range of the species over the past ten years has been c.19-21% (Global Forest Watch 2024, based on data from Hansen et al. [2013] and methods therein). However, forest loss data alone likely underestimate declines as they do not account for habitat degradation, which is likely to cause declines in this forest-dependent species and has been substantial in scale and intensity across the species' range (Global Forest Watch 2024, based on data from Grantham et al. [2020]), particularly as the species has been shown to occur in reduced numbers and abundance in selectively logged areas (Lambert 1992, Ansell et al. 2010).
On Sumatra, the species has only been recorded on three occasions from three separate areas this century (Hutchinson 2006, Kemp 2008 in Hua et al. 2011, Hua et al. 2011). There is a need for much improved survey coverage (Hua et al. 2011) and the species seems to always occur at low densities (e.g., see historical records in BirdLife International [2001] and Hua et al. [2011]), including in intact suitable habitat (Slik and van Balen 2005, Ansell et al. 2010). However, this rarity is reasonably partly caused by the high levels of deforestation and habitat degradation on Sumatra (Grantham et al. 2020). Without improved survey effort, it is difficult to infer local extinctions, but it seems likely that the species has disappeared from Way Kambas National Park, with one pair recorded in 1989 (Lewis et al. 1989 in BirdLife International 2001) and no records since this time despite reasonable survey coverage (eBird 2024). Regardless, these disjunct records of a small number of individuals highlight the very high risk of local extinctions in these areas, and on Sumatra in general.
There is little information specific to this species, but it is very likely that it is also impacted by the cage bird trade. Cyornis flycatchers are highly popular in the cage bird trade (BirdLife International 2001, Eaton et al. 2021), and the lack of reports of C. caerulatus in trade is likely due to misidentification rather than low demand. The species is clearly traded at higher numbers than available reports suggest, with one seizure from east Java in 2018 reporting 154 individuals shipped from southern Kalimantan (TRAFFIC 2024). The increasing rarity of the highly in demand C. banyumas (Chng et al. 2015, Kirwan et al. 2021, BirdLife International 2024) may also suggest that C. caerulatus will be increasingly targeted to cover this gap in the market. Symes et al. (2018) also predicted a reduction of c. 34% over the past ten years from trapping by assigning probability curves according to expert opinion on trade desirability in conjunction with accessibility (based on a distance to forest edge from remote sensed forest data). This analysis had no term to account for reproduction, and was largely speculative, but provides evidence that the species is certainly targeted for trade locally and occurs in areas accessible to poachers.
The impacts of trade and habitat loss/degradation on the population of C. caerulatus are suspected to be much higher than current available data suggests. Furthermore, Maxent habitat modelling using Special Report on Emissions Scenarios A1B and B1 predict a further c. 6-26% decline in suitable habitat on Borneo by 2050 caused by climate change (Singh et al. 2021). The cumulative impacts of these pervasive threats suggest ongoing declines in the population are likely in the range of 20-40% over ten years.
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
Recommended citation
BirdLife International (2024) Species factsheet: Large-billed Blue Flycatcher Cyornis caerulatus. Downloaded from
https://datazone.birdlife.org/species/factsheet/large-billed-blue-flycatcher-cyornis-caerulatus on 23/12/2024.
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 23/12/2024.
