VU
Henderson Reed-warbler Acrocephalus taiti



Taxonomy

Taxonomic note

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.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - D2

Red List history
Year Category Criteria
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 -
Extent of occurrence (EOO)

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 46 medium
Extent of Occurrence breeding/resident (km2) 37
Number of locations 1 -
Fragmentation -
Population and trend
Estimate Data quality Derivation Year of estimate
No. of mature individuals 7200 medium estimated 1987
Population trend Stable poor suspected -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 0 - - -
Decline (10 years/3 generation past and future) 0 - - -
Number of subpopulations 1 - - -
Largest subpopulations 100 - - -
Generation length (yrs) 6.9 - - -

Population justification: In 1987, it was found to be abundant throughout the island, with an estimated total population of c.10,800 (adjusted to 13,000 when using the correct island area), and available habitat apparently saturated (Graves 1992). In 1991-1992 surveys estimated the population at 9,500 (11,000 using corrected island area) individuals and in both 2003 and 2011, there was no striking change evident (M. Brooke in litt. 2007, 2012), and the population was assumed to be stable. In 2015, the population at 25 point count locations was estimated to be 180 (95% CI 147 - 224) individuals, and the trend from 2011 to 2015 was estimated to be increasing substantially (mean 0.191, 95% CI 0.153 - 0.231) after the temporary relief from rat predation following the (failed) eradication attempt in 2011. If we assume that warblers counted at point count locations ranged up to 100 m from the location, and that 73% of the island is suitable habitat, the global estimate for the species in 2015 would be 7194 (95%CI 5875 - 8593) individuals. Graves (1992) estimated the population at 10,800 individuals, equating to c.7,200 mature individuals, and thus similar to Graves' (1992) extrapolations which were based on an entirely different census method.

Trend justification: There are no new data on population trends; however, the species's entire range is within a World Heritage Site and despite limited predation by Pacific rats Rattus exulans it is thought to be stable.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Pitcairn Islands (to UK) N Extant 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   Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Biological resource use Gathering terrestrial plants Timing Scope Severity Impact
Ongoing Minority (<50%) No decline Low Impact: 4
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
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases Timing Scope Severity Impact
Future Whole (>90%) Very Rapid Declines Medium Impact: 7
Stresses
Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases 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 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 Timing Scope Severity Impact
Future Whole (>90%) Very Rapid Declines Medium Impact: 7
Stresses
Species mortality

Recommended citation
BirdLife International (2019) Species factsheet: Acrocephalus taiti. Downloaded from http://www.birdlife.org on 26/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/08/2019.