NT
Dapple-throat Arcanator orostruthus



Taxonomy

Taxonomic note

Arcanator orostruthus (del Hoyo and Collar 2016) was previously placed in the genus Modulatrix following Dowsett & Forbes-Watson (1993); Sibley & Monroe (1990, 1993).

 

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
- - C2a(i)

Red List history
Year Category Criteria
2021 Near Threatened C2a(i)
2016 Vulnerable B1ab(i,ii,iii,v)
2013 Vulnerable B1ab(i,ii,iii,v)
2012 Vulnerable B1ab(i,ii,iii,v)
2008 Vulnerable B1a+b(i,ii,iii,v)
2004 Vulnerable
2000 Vulnerable
1996 Vulnerable
1994 Vulnerable
1988 Threatened
Species attributes

Migratory status not a migrant Forest dependency High
Land mass type Land-mass type - continent
Average mass 33 g
Distribution

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 280,200 medium
Extent of Occurrence breeding/resident (km2) 10,532
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 1000-2499 poor suspected 2021
Population trend Decreasing medium 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) 10-20 - - -
Decline (10 years/3 generation past and future) 10-20 - - -
Number of subpopulations 3-5 - - -
Percentage in largest subpopulation 1-89 - - -
Generation length (yrs) 3.48 - - -

Population justification: The population in Mozambique was estimated by Dowsett-Lemaire (2010) to be 600-1,000 mature individuals on Mt Namuli, and up to 200 mature individuals on Mt Mabu. Since those surveys, large swathes of forest has been lost (J. Timberlake in litt. 2020), and the population in Mozambique is now likely to be <1,000 total individuals (B. Phalan in litt. 2020). This species was recently discovered on the Njesi Plateau in Mozambique (Jones et al. 2017), with the population there likely to be smaller than that on Namuli (B. Phalan in litt. 2020). The total population in the East Usambaras was considered to possibly only number a few pairs (Borghesio et al. 2008), and is still considered to be very rare (Neate-Clegg et al. 2021). The species in the Udzungwa Mountains may have undergone substantial declines owing to the effect of forest loss and degradation on its localised population (B. Phalan in litt. 2020), and the population may therefore be very small. In the absence of more conclusive data, the population size is tentatively suspected to fall into the band of 1,000-2,499 mature individuals. It is also tentatively assumed, based on available data, that the largest subpopulation contains <1,000 mature individuals.

Trend justification: The species's population is inferred to be declining in line with the fragmentation and degradation of mid-elevation forests within its range. Due to habitat loss (Dowsett-Lemaire, 2010; Timberlake, 2017), it is suspected to be declining at a rate of 10-20% over three generations (10.5 years [Bird et al. 2020]).


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

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Mozambique Mount Namuli
Tanzania Udzungwa National Park
Tanzania Udzungwa Mountains
Tanzania East Usambara Mountains
Tanzania Udzungwa Mountain Range
Mozambique Mount Mabu

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Forest Subtropical/Tropical Moist Montane major resident
Altitude 900 - 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 Majority (50-90%) Slow, Significant Declines Medium Impact: 6
Stresses
Ecosystem degradation, Ecosystem conversion
Biological resource use Logging & wood harvesting - Unintentional effects: (large scale) [harvest] Timing Scope Severity Impact
Future Minority (<50%) Slow, Significant Declines Low Impact: 3
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
Future Whole (>90%) Unknown Unknown
Stresses
Indirect ecosystem effects, Ecosystem degradation
Natural system modifications Fire & fire suppression - Increase in fire frequency/intensity Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Stresses
Ecosystem degradation
Transportation & service corridors Roads & railroads Timing Scope Severity Impact
Ongoing Minority (<50%) Slow, Significant Declines Low Impact: 5
Stresses
Ecosystem degradation, Ecosystem conversion

Recommended citation
BirdLife International (2022) Species factsheet: Arcanator orostruthus. Downloaded from http://www.birdlife.org on 29/01/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/01/2022.