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

Taxonomic note

Zosterornis nigrorum (del Hoyo and Collar 2016) was previously listed as Stachyris nigrorum.

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
-	B1ab(iii,v)+2ab(iii,v); C2a(ii)	B1ab(iii,v)+2ab(iii,v); C2a(i,ii); D1

Red List history

Year	Category	Criteria
2024	Endangered	B1ab(iii,v)+2ab(iii,v); C2a(ii)
2016	Endangered	B1ab(i,ii,iii,iv,v)
2012	Endangered	B1ab(i,ii,iii,iv,v)
2008	Endangered	B1a+b(i,ii,iii,iv,v)
2004	Endangered
2000	Endangered
1996	Endangered
1994	Endangered
1988	Threatened

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

	Estimate	Data quality
Area of Occupancy (breeding/resident)	240 km2	poor
Number of locations	3-10	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	750-2300 mature individuals	poor	estimated	2024
Population trend	decreasing	poor	inferred	-
Generation length	3 years	-	-	-
Number of subpopulations	1-2,1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification:

The population is estimated as 1,100-2,500 individuals, and 750-2,200 mature individuals. This estimate is calculated from 2017-2021 surveys for Z. nigrorum on Mt Talinis (Oracion et al. 2022). The surveys yielded an encounter rate of 0.034 birds per hour. This rate was transformed into a density per km² using the stated survey design of 8 km total transect length per survey across a total of 175.8 hours (Oracion et al. 2022). The density calculation assumed a detection width of 25 m either side of the transect. The density was extrapolated to a minimum area of suitable habitat of 73 km² and maximum area of 164 km² (calculated by sRedList [2023] using data from Jung et al. [2020]). This method gave a population estimate of 1,091-2,451, rounded to 1,100-2,500. Not all of these are likely to be mature individuals although the proportion of mature individuals is likely high given this species' short generation length. The estimate is revised to 750-2,300 mature individuals.

Large areas of the species range have not been surveyed, or have not been surveyed consistently or thoroughly. This is reflected in the rates reported by Oracion et al. (2022) which range from 0/hour to 2.7/hour. Additionally, the exact habitat requirements and tolerance of the species for degraded habitats are unknown. Therefore, this range captures the uncertainty in the population, whilst accurately reflecting the consistent low reporting rates of the species (Oracion et al. 2022, eBird 2024).

Trend justification: In 1992, one survey on Mt. Talinis recorded 76 Negros Striped-babbler in a single day, a detection rate of 9.5 birds per hour (Brooks et al. 1992). The species was described as one of the most frequently recorded birds in the area (Brooks et al. 1992). Subsequent surveys have shown continuing decline in the detection rates of the species, from 9.5/hour to 1.8/hour in 2007, to 0.2/hour from surveys between 2017-2021 (Oracion et al. 2022). From the surveys collated by Oracion et al. (2022), the highest number of birds recorded in a single day was 12. If the Brooks et al. (1992) estimate was an anomaly, the detection rates from 2007-2021 still show a clear decline in detection rates (Oracion et al. 2022).Given the continuing degradation of habitat across the species' range, these reporting rates are very likely representative of a continuing decline in the number of mature individuals.

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

Country/Territory	IBA Name
Philippines	Cuernos de Negros
Philippines	Mount Kanla-on Natural Park

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Plantations	marginal	resident
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	900 - 1600 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%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Annual & perennial non-timber crops - Shifting agriculture	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Unknown		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation

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Recommended citation
BirdLife International (2024) Species factsheet: Negros Striped Babbler Zosterornis nigrorum. Downloaded from https://datazone.birdlife.org/species/factsheet/negros-striped-babbler-zosterornis-nigrorum on 22/11/2024.
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 22/11/2024.