• 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
-	A2b; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(i)	A2b; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(i); D1

Red List history

Year	Category	Criteria
2021	Endangered	A2b; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(i)
2016	Critically Endangered	B2ab(i,ii,iii,iv,v)
2015	Critically Endangered	B2ab(i,ii,iii,iv,v)
2012	Critically Endangered	B2ab(i,ii,iii,iv,v)
2009	Critically Endangered	B2a+b(i,ii,iii,iv,v)
2008	Critically Endangered
2004	Critically Endangered
2000	Critically Endangered
1996	Critically Endangered
1994	Critically Endangered
1988	Threatened

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	130 km2	medium
Area of Occupancy (breeding/resident)	20 km2	good
Number of locations	3	-
Severely fragmented?	yes	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	250-999 mature individuals	good	estimated	2010
Population trend	decreasing	poor	inferred	-
Rate of change over the past 10 years/3 generations (longer of the two periods)	60-70%	-	-	-
Generation length	3.86 years	-	-	-
Number of subpopulations	3	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: Waiyaki and Samba (2000) estimated the population to number 1,400 individuals, which is roughly equivalent to 930 mature individuals. Galbusera et al. (2000) estimated the following subpopulation sizes: Mbololo 1,059, Ngangao 250, and Chawia 38, which totals 1,347 individuals, and c.800 mature individuals. Plot-based Capture-Mark-Recapture models by L. Cousseau (as reported by L. Lens in litt. 2019) on data collected between 2000-2010, and the comparisons of annual survival rates during sub-periods between 2000-2010 with those calculated for 1997-2000, suggest the following rates of decline occurred in each subpopulation between 2000-2010: Mbololo (73%), Ngangao (36%), Chawia (41%). The subpopulation sizes in 2010 may therefore have been more like: Mbololo 289, Ngangao 159, and Chawia 23, which would equate to c.280 mature individuals (L. Lens in litt. 2019).

However, the initial figures by Galbusera et al. (2000) were produced via extrapolation. Hence, these figures assume that densities are constant throughout the whole fragment, which is unlikely due to edge effects and that even in dense homogenous forest, density varies significantly. Additionally, using the CMR models to assess absolute population estimates relies on delicate assumptions. Therefore, there is significant uncertainty around the true population size. To account for this, the population estimate is placed in the band 250-999 mature individuals. 

Trend justification: Based on the figures from Galbusera et al. (2000) data from the Capture-Mark-Recapture models (L. Lens in litt. 2019), the subpopulations may have reduced from 1,059-289 (Mbololo), 250-159 (Ngangao) and 38-23 (Chawia). Overall, this equates to an overall population decline of 63.4% over three generations. Hence, the population decline is inferred to fall in the band 60-70% over three generations.

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

Country/Territory	IBA Name
Kenya	Taita Hills Forests

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	1200 - 2000 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder farming	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Rapid Declines		High Impact: 8
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Wood & pulp plantations - Scale Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Rapid Declines		High Impact: 8
		Stresses Ecosystem degradation, Ecosystem conversion
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Unspecified species	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Natural system modifications	Fire & fire suppression - Increase in fire frequency/intensity	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Causing/Could cause fluctuations		Medium Impact: 6
		Stresses Ecosystem conversion, Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Taita Thrush Turdus helleri. Downloaded from https://datazone.birdlife.org/species/factsheet/taita-thrush-turdus-helleri 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.