CR
Dwarf Ibis Bostrychia bocagei



Taxonomy

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
C2a(ii) B1ab(ii,iii,v)+2ab(ii,iii,v); C2a(i,ii); D B1ab(ii,iii,v)+2ab(ii,iii,v); C2a(i,ii); D1

Red List history
Year Category Criteria
2021 Critically Endangered C2a(ii)
2018 Critically Endangered C2a(ii)
2016 Critically Endangered C2a(ii)
2015 Critically Endangered C2a(ii)
2013 Critically Endangered C2a(ii)
2012 Critically Endangered C2a(ii)
2011 Critically Endangered C2a(ii)
2010 Critically Endangered C2a(ii)
2009 Critically Endangered C2a(ii)
2008 Critically Endangered
2007 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 Average mass -
Distribution

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 140 medium
Extent of Occurrence breeding/resident (km2) 192
Number of locations 1 -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 130-1700 poor estimated 2020
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 1 - - -
Percentage in largest subpopulation 100 - - -
Generation length (yrs) 7.1 - - -

Population justification: Based on a range-size assumption of 100 km2, using density surface modelling and plot sampling extrapolations, the population was estimated to be between 347-4,578 individuals (Azevedo 2015). Assuming this species exists in the smallest area estimate of 55 km2 (Soares et al. 2020), the estimated population would therefore be roughly 190-2,500 individuals, which would roughly equate to 130-1,700 mature individuals.
The worst-case scenario of <200 individuals is not consistent with the number of ibises that hunters reported killing (Sampaio et al. 2016), however the best-case scenarios still produce very low population estimates.

Trend justification: The population is inferred to be declining as a result of ongoing hunting pressure (Sampaio et al. 2016). Hunting pressure is suspected to be high, but the resulting rate of decline is unclear. It may also be suffering habitat loss as a result of an oil palm plantation.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
São Tomé e Príncipe N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
São Tomé e Príncipe São Tomé lowland forests
São Tomé e Príncipe Parque Natural Obô de São Tomé e Zona Tampão

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Forest Subtropical/Tropical Moist Lowland major resident
Forest Subtropical/Tropical Moist Montane marginal resident
Wetlands (inland) Permanent Freshwater Lakes (over 8ha) suitable resident
Wetlands (inland) Permanent Rivers/Streams/Creeks (includes waterfalls) suitable resident
Altitude 100 - 1000 m Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Agriculture & aquaculture Annual & perennial non-timber crops - Scale Unknown/Unrecorded Timing Scope Severity Impact
Past, Unlikely to Return Majority (50-90%) Rapid Declines Past Impact
Stresses
Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture Annual & perennial non-timber crops - Small-holder farming Timing Scope Severity Impact
Future Minority (<50%) Very Rapid Declines Low Impact: 5
Stresses
Ecosystem degradation, Ecosystem conversion
Biological resource use Hunting & trapping terrestrial animals - Intentional use (species is the target) Timing Scope Severity Impact
Ongoing Majority (50-90%) Rapid Declines Medium Impact: 7
Stresses
Species mortality
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 conversion
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Cercopithecus mona Timing Scope Severity Impact
Ongoing Majority (50-90%) Unknown Unknown
Stresses
Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Civettictis civetta Timing Scope Severity Impact
Ongoing Majority (50-90%) Unknown Unknown
Stresses
Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Felis catus Timing Scope Severity Impact
Ongoing Majority (50-90%) Unknown Unknown
Stresses
Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Rattus rattus Timing Scope Severity Impact
Ongoing Majority (50-90%) Unknown Unknown
Stresses
Reduced reproductive success
Natural system modifications Dams & water management/use - Large dams Timing Scope Severity Impact
Future Majority (50-90%) Rapid Declines Low Impact: 5
Stresses
Species disturbance, Ecosystem degradation, Ecosystem conversion
Transportation & service corridors Roads & railroads Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Stresses
Ecosystem conversion

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Food - human - - Non-trivial Recent

Recommended citation
BirdLife International (2022) Species factsheet: Bostrychia bocagei. Downloaded from http://www.birdlife.org on 03/10/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 03/10/2022.