VU
Henderson Island Reed-warbler Acrocephalus taiti



Taxonomy

Taxonomic note
See A. vaughani. Monotypic.

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
- - D2

Red List history
Year Category Criteria
2022 Vulnerable D2
2016 Vulnerable D2
2012 Vulnerable D2
2008 Vulnerable D2
2004 Vulnerable
2000 Vulnerable
1994 Not Recognised
1988 Not Recognised
Species attributes

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

Estimate Data quality
Extent of Occurrence (breeding/resident) 80 km2 medium
Area of Occupancy (breeding/resident) 80 km2
Number of locations 1 -
Severely fragmented? no -
Population
Estimate Data quality Derivation Year of estimate
Population size 4000-8600 mature individuals medium estimated 1992
Population trend stable poor estimated -
Generation length 5.46 years - - -
Number of subpopulations 1 - - -
Percentage of mature individuals in largest subpopulation 100% - - -

Population justification: Estimates over the past three decades have been broadly congruent. In 1987, the population was estimated to number c.13,000 individuals (value adjusted to correct island area) and available habitat was apparently saturated (Graves 1992). In 1991-1992 surveys, using a different technique, 11,000 individuals were estimated, a number also thought true in 2003 and 2011 (M. Brooke in litt. 2007-2012). In 2015, the population at 25 point count locations was extrapolated to the area of suitable habitat, equal to 7,194 (5,875-8,593) individuals (Bond et al. 2019a). Because the latter estimate was based on detectability distances that were not empirically determined, these results are treated with some caution, although their proximity to earlier data suggest that the population size of this species is between 6,000 and 13,000 individuals, thought equivalent to c.4,000-8,600 mature individuals.

Trend justification: Although direct comparison is hampered by methodological differences, count data between 1987 and 2015 are comparable (Graves 1992, Brooke and Jones 1995, Bond et al. 2019a) and do not indicate any decline. Since 2015, there is no identified threat that may have caused a reduction.


Country/territory distribution
Country/Territory Presence Origin Resident Breeding visitor Non-breeding visitor Passage migrant
Pitcairn Islands (to UK) extant native yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Pitcairn Islands (to UK) Henderson Island

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Forest Subtropical/Tropical Dry major resident
Altitude 0 - 330 m Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Rattus exulans Timing Scope Severity Impact
Ongoing Whole (>90%) Negligible declines Medium Impact: 6
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Rattus norvegicus Timing Scope Severity Impact
Future Whole (>90%) Very Rapid Declines Medium Impact: 7
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Rattus rattus Timing Scope Severity Impact
Future Whole (>90%) Very Rapid Declines Medium Impact: 7
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Unspecified species Timing Scope Severity Impact
Future Whole (>90%) Very Rapid Declines Medium Impact: 7
Stresses
Species mortality

Recommended citation
BirdLife International (2024) Species factsheet: Henderson Island Reed-warbler Acrocephalus taiti. Downloaded from https://datazone.birdlife.org/species/factsheet/henderson-island-reed-warbler-acrocephalus-taiti on 23/12/2024.
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 23/12/2024.