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Inaccessible Bunting Nesospiza acunhae

Justification
Although this species is abundant within its extremely small range and is not currently thought to be declining, the potential arrival of invasive species on Inaccessible Island could lead to extremely rapid declines such that the species could become Critically Endangered or Extinct within a short time period (as has happened on Tristan da Cunha). It is consequently classified as Vulnerable.

Taxonomic source(s)
Ryan, P. G. 2008. Taxonomic and conservation implications of ecological speciation in Nesospiza buntings at Tristan da Cunha. Bird Conservation International 18(1): 20-29.

Taxonomic note
Nesospiza acunhae (Sibley and Monroe 1990, 1993) has been split into N. acunhae (Inaccessible Island) and N. questi (Nightingale Island), while subspecies N. wilkinsi dunnei (Inaccessible Island) has been transferred to N. acunhae following Ryan et al. (2007) and Ryan (2008) who provide compelling phylogenetic evidence for this arrangement and point out the morphological and vocal differences supporting the treatment of paraphyletic forms questi and acunhae as species.

Distribution and population
Nesospiza acunhae occurs on Inaccessible Island, Tristan da Cunha (St Helena to UK) in the South Atlantic Ocean (Ryan 2008). It became extinct on the main island of Tristan da Cunha before the end of the 19th century (Fraser and Briggs 1992). It is abundant, especially on coastal tussock, with an estimated total population of 23,400 mature individuals comprising three distinctive colour morphs and a large number of 'hybrids' between these morphs (Ryan 2008).

Population justification
The species is abundant on Inaccessible Island, especially in coastal tussock, with the total population estimated at 23,400 mature individuals (Ryan 2008).

Trend justification
The species's population is suspected to be stable owing to the absence of any serious and immediate threats.

Ecology
On Inaccessible, the upland form occurs primarily in fern-bush and wet heath between 300-600 m and has a brighter yellow/green coloration than the lowland form, which is found mainly in tussock-grassland on the coastal slopes (Ryan 2008). It is probable that the variation in plumage between the forms is due to dietary differences (Ryan et al. 1994), with 'bright' birds feeding more extensively on carotenoid-rich fruits of Nertera than 'dull' ones, which feed predominantly on flowers and seedheads of Spartina species.

Threats
Despite its name, Inaccessible is now more accessible to islanders via a fisheries patrol vessel and several rigid inflatables based at Tristan (P. G. Ryan in litt. 1999, 2012). This species is thus permanently at risk from the accidental introduction of mammalian predators which could prey on eggs, chicks and nesting birds. Another threat is the invasion of the introduced New Zealand flax Phormium tenax into areas of Phylica (P. G. Ryan in litt. 1999) resulting in the possible degradation of its habitat, but ongoing control measures started in 2004 have reduced this risk. The large-billed coastal form N. a. dunnei could be threatened by reduced fruit loads on Phylica trees infested by an introduced scale bug and associated sooty moulds.

Conservation Actions Underway
Inaccessible is a nature reserve and, although Tristan Islanders retain the right to collect driftwood and guano, other access is restricted (Cooper et. al. 1995). A management plan for the island was published in 2001 (Ryan & Glass 2001). Inaccessible was added to the Gough Island World Heritage Site in the early 2000s. New Zealand flax has been removed from coastal and plateau areas and is now confined to c.300 m of cliffs around the Waterfall (P. G. Ryan in litt. 2012). Conservation Actions Proposed
Carry out surveys to obtain an up-to-date population estimate. Conduct regular surveys to monitor population trends. Minimise the risk of introduction of exotic animal or plant taxa to any of the islands by strict controls on visits and promoting awareness of the dangers of inter-island transfers (P. G. Ryan in litt. 1999). Complete eradication of remaining New Zealand flax from Inaccessible (P. G. Ryan in litt. 2012). Evaluate the possible reintroduction of birds to Tristan da Cunha in the long term (P. G. Ryan in litt. 1999).


References
Cooper, J.; Ryan, P. G.; Andrew, T. G. 1995. Conservation status of the Tristan da Cunha Islands. In: Dingwall, P.R. (ed.), Progress in conservation of the subantarctic islands, pp. 59-70. IUCN-World Conservation Union, Gland, Switzerland.

Fraser, M. W.; Briggs, D. J. 1992. New information on the Nesospiza buntings at Inaccessible Island, Tristan da Cunha, and notes on their conservation. Bulletin of the British Ornithologists' Club 112: 191-205.

Ryan, P. G. & Glass, J. P. 2001. Inaccessible Island Nature Reserve Management Plan. Government of Tristan da Cunha, Edinburgh, Tristan da Cunha.

Ryan, P. G. 1992. The ecology and evolution of Nesospiza buntings. Dissertation. Ph.D., University of Cape Town.

Ryan, P. G. 2008. Taxonomic and conservation implications of ecological speciation in Nesospiza buntings at Tristan da Cunha. Bird Conservation International 18(1): 20-29.

Ryan, P. G.; Bloomer, P.; Moloney, C. L.; Grant, T.; Delport, W. 2007. Adaptive speciation in South Atlantic island finches. Science 315(1420–1423).

Ryan, P. G.; Moloney, C. L.; Hudon, J. 1994. Color variation and hybridization among Nesospiza buntings on Inaccessible Island, Tristan da Cunha. The Auk 111: 314-327.

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

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Text account compilers
Calvert, R., Symes, A.

Contributors
Cooper, J., Ryan, P.G.

IUCN Red List evaluators
Butchart, S., Taylor, J.

Recommended citation
BirdLife International (2014) Species factsheet: Nesospiza acunhae. Downloaded from http://www.birdlife.org on 29/11/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/11/2014.

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 - Tristan bunting (Nesospiza acunhae) 0

Key facts
Current IUCN Red List category Vulnerable
Family Emberizidae (Buntings, American sparrows and allies)
Species name author Cabanis, 1873
Population size 23400 mature individuals
Population trend Stable
Distribution size (breeding/resident) 14 km2
Country endemic? Yes
Links to further information
- Additional Information on this species