EN
Taita Thrush Turdus helleri



Taxonomy

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
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
Species attributes

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

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 130 medium
Extent of Occurrence breeding/resident (km2) 20 good
Number of locations 3 -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 250-999 good estimated 2010
Population trend Decreasing poor inferred -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) - - -
Decline (10 years/3 generation past and future) - - -
Number of subpopulations 3 - - -
Percentage in largest subpopulation 1-89 - - -
Generation length (yrs) 3.86 - - -

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 distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Kenya N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Kenya Taita Hills Forests

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

Threats & impact
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

Recommended citation
BirdLife International (2022) Species factsheet: Turdus helleri. Downloaded from http://www.birdlife.org on 23/05/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/05/2022.