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Henderson Reed-warbler Acrocephalus taiti

Justification
This species qualifies as Vulnerable as it is only found on one small island, where it remains at risk from the accidental introduction of alien species, especially mammalian predators.

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

Taxonomic note
Acrocephalus vaughani (Sibley and Monroe 1990) has been split into A. vaughani, A. rimatarae and A. taiti following Sibley and Monroe (1993). Note that Collar et al. (1994) followed Sibley and Monroe (1990) in treating these three taxa as a single species, A. vaughani.

Identification
17 cm. Large warbler with relatively short bill. Adult olive-brown above, white below with slight yellowish tinge. Mottled olive-brown and white crown, rest of head white with dark streak through eye. White feathers variably and often asymmetrically scattered among darker feathers. Some individuals are nearly all white. Voice No song. Call a harsh, short note.

Distribution and population
Acrocephalus taiti is endemic to Henderson, an uninhabited island in the Pitcairn Islands (to UK). In 1987, it was found to be abundant throughout the island, with an estimated total population of c.10,800 and available habitat apparently saturated (Graves 1992). In 1991-1992 surveys estimated the population at 9,500 individuals and in both 2003 and 2011, there was no striking change evident (M. Brooke in litt. 2007, 2012). The population is assumed to be stable.

Population justification
Graves (1992) estimated the population at 10,800 individuals, equating to c.7,200 mature individuals.

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.

Ecology
This is a forest species, typically found in family groups, foraging at all levels, and has a varied diet, which is known to include several species of land snails, ants, flies, beetles, cockroaches, large wasps, seeds and fruit pulp (Graves 1992). It has a well-defined breeding period from late August to early January, nesting in a wide variety of tree species in the lower canopy of forest. The species breeds either in pairs or trios, commonly of unrelated birds, probably a consequence of the island's stable habitat and climax forest, where young birds may be more able to secure a nesting territory when belonging to a trio than a pair (Brooke and Hartley 1995). Clutch-size is two to three and, once hatched, most chicks fledge (Brooke and Hartley 1995).

Threats
Although Pacific rat R. exulans was, until recently, common throughout the island, and has been observed in the upper branches of trees, the warbler has apparently adapted to its presence or is at least able to coexist with it (Graves 1992). However, the temporary recovery of A. vaughani on Pitcairn Island, after the removal of feral cats and reduction of rats, indicates that rats probably suppress the population (B. Bell verbally 1999). In August 2011, a rat eradication operation was carried out on Henderson Island to eradicate R. exulans from the island (J. Hall in litt. 2012). The accidental introduction of other predators (especially black rat R. rattus) and diseases remain a threat as the island, although isolated, is visited by the passengers and crew of passing ships (Graves 1992).

Conservation Actions Underway
In 1988, Henderson was designated a World Heritage Site. Following a feasibility study (Brooke and Towns 2008) a rat eradication operation was carried out on Henderson Island in August 2011 (J. Hall in litt. 2012). A follow-up monitoring expedition is planned for 2013 to assess the success of the rat eradication.Conservation Actions Proposed
Periodically resurvey to monitor numbers and trends. Ensure that further alien species are not accidentally introduced to Henderson.


Related state of the world's birds case studies

References
Brooke, M. De L.; Hartley, I. R. 1995. Nesting Henderson Reed-warblers (Acrocephalus vaughani taiti) studied by DNA fingerprinting: unrelated coalitions in a stable habitat? The Auk 112: 77-86.

Graves, G. R. 1992. The endemic land birds of Henderson Island, southeastern Polynesia: notes on natural history and conservation. Wilson Bulletin 104: 32-43.

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

Sibley, C. G.; Monroe, B. L. 1993. A supplement to 'Distribution and taxonomy of birds of the world'. Yale University Press, New Haven, USA.

Further web sources of information
Explore HBW Alive for further information on this species

View photos and videos and hear sounds of this species from the Internet Bird Collection

Text account compilers
Mahood, S., O'Brien, A., Shutes, S., Stattersfield, A., Derhé, M.

Contributors
Brooke, M., Hall, J., Bell, B.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Acrocephalus taiti. Downloaded from http://www.birdlife.org on 02/10/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/10/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Henderson reed-warbler (Acrocephalus taiti) 0

Key facts
Current IUCN Red List category Vulnerable
Family Sylviidae (Old World warblers)
Species name author Ogilvie-Grant, 1913
Population size 7200 mature individuals
Population trend Stable
Distribution size (breeding/resident) 41 km2
Country endemic? Yes
Links to further information
- Additional Information on this species