• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

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.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	A2c+3c+4c

Red List history

Year	Category	Criteria
2023	Vulnerable	A2c+3c+4c
2016	Vulnerable	A2c+3c+4c
2012	Vulnerable	A2c+3c+4c
2008	Vulnerable	A2c; A3c; A4c
2004	Vulnerable
2000	Vulnerable
1994	Lower Risk/Near Threatened
1988	Lower Risk/Least Concern

Migratory status	not a migrant	Forest dependency	medium
Land-mass type	shelf island	Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	1,600,000 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	unknown	poor	-	-
Population trend	decreasing	poor	suspected	2016-2027
Rate of change over the past 10 years/3 generations (longer of the two periods)	19-42,30-40%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	19-42,30-40%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	19-42,30-40%	-	-	-
Generation length	3.5 years	-	-	-
Number of subpopulations	2-70	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: The population size of this species has not been quantified, however this species is considered a specialist of stunted forest types (Sheldon 1987), the area of which is difficult to map. Within suitable habitat, it may be regularly observed and can be quite common (Posa and Marques 2012, RER 2017, Eaton et al. 2021, eBird 2022) but the area of available habitat has greatly diminished over the past 20 years, such that the population size, although unquantified here, is likely to be much smaller than three generations ago. On Sumatra, the area of suitable habitat is small and greatly fragmented, with recent records from only a handful of sites on the island's east; here, however, it is always thought to have been rare (see review by van Marle and Voous 1988). On Borneo, the area of habitat is much larger and records (Mann 2008, eBird 2022) suggest it remains widespread.

Trend justification: Setornis criniger is thought to be declining rapidly in response to extensive forest cover loss across its range. In the absence of population data, forest cover loss is used as a proxy to estimate the rate of reduction over the past three generations (10.5 years; Bird et al. 2020), however doing this accurately relies on robust knowledge of the species' distribution when forest cover was more extensive. There is, however, much uncertainty on how widespread it was on Sumatra historically, and its elevational limits on Borneo (where it has on occasion been recorded in kerangas forest up to 1,000 m [Mann 2008]). Under a range of mapped scenarios, forest cover loss in the species' mapped range is thought to have reduced by 19-42% over the last three generations (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein). Precautionarily, towards the upper limit of these losses (30-40%) is accepted here given the species confinement to specialised habitat. This rate of loss is also suspected to occur into the future, with comparatively little of the species' range circumscribed by protected areas (UNEP-WCMC 2022), and most of it accessible for exploitation.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Brunei	extant	native	yes
Indonesia	extant	native	yes
Malaysia	extant	native	yes

Country/Territory	IBA Name
Brunei	Belait Swamp Forest
Brunei	Southern Ladan Hills
Indonesia	Bukit Baling
Indonesia	Gunung Palung
Indonesia	Hutan Rawa Gambut Siak-Kampar
Indonesia	Kayan Mentarang
Indonesia	Tanjung Puting
Indonesia	Tesso Nilo
Indonesia	Ulu Barito
Malaysia	Bako-Buntal Bay
Malaysia	Danum Valley Conservation Area
Malaysia	Dulit Range
Malaysia	Klias peninsula
Malaysia	Lambir Hills National Park
Malaysia	Lanjak Entimau Wildlife Sanctuary
Malaysia	Mulu - Buda Protected Area
Malaysia	Niah National Park
Malaysia	Sadong-Saribas coast
Malaysia	Similajau National Park
Malaysia	Tabin Wildlife Reserve
Malaysia	Tanjung Datu-Samunsam Protected Area

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Plantations	suitable	resident
Forest	Subtropical/Tropical Moist Lowland	suitable	resident
Forest	Subtropical/Tropical Swamp	major	resident
Altitude	0 - 1000 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Agro-industry farming	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Annual & perennial non-timber crops - Shifting agriculture	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Wood & pulp plantations - Agro-industry plantations	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (large scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Natural system modifications	Fire & fire suppression - Trend Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation
Residential & commercial development	Commercial & industrial areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Hook-billed Bulbul Setornis criniger. Downloaded from https://datazone.birdlife.org/species/factsheet/hook-billed-bulbul-setornis-criniger 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.