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Large-billed Reed-warbler Acrocephalus orinus

This species is listed as Data Deficient because, despite the recent increase in records, there is still insufficient information available to conduct a robust assessment of its threat status.

Taxonomic note
Acrocephalus stentoreus (Sibley and Monroe 1990, 1993) has been split into A. stentoreus and A. orinus following Bensch and Pearson (2002). A. australis, a cross-regional species, is retained as a separate species contra Christidis and Boles (1994) who include australis as a subspecies of A. stentoreus.

Distribution and population
Acrocephalus orinus was known until relatively recently from only from one specimen, collected in the Sutlej Valley near Rampoor, Himachal Pradesh, India in November 1867. In March 2006, one was trapped at Laem Phak Bia, Phatchaburi Province, south-west Thailand, 3,100 km from the type locality (Round et al. 2007), and soon afterwards a further museum specimen was located (taken in Uttar Pradesh, India in October 1869, and previously labelled as A. dumetorum) (Anon 2007, Pearson et al. 2008). Subsequent searches have located additional museum specimens from Central Asia, India and Myanmar (Svensson et al. 2008). In April 2007 a bird apparently of this species was observed and photographed near Chintamani Kar Bird Sanctuary, Narendrapur, West Bengal, India (Round and Kennerley 2007). No other individuals were trapped at the site of the 2006 bird during 2000-2006 and the lack of records from this comparatively well-studied country suggest it is likely to be only an extreme vagrant to Thailand (Round et al. 2007). Fieldwork conducted in Badakshan province, north-eastern Afghanistan, located a likely breeding population in 2008-2009 (Timmins et al. 2009, 2010). In spring 2009, a probable breeding population was also located in the Badakshan region of Tajikistan (Ayé et al. 2010). It may be a long-distance migrant like A. dumetorum, breeding in the Palearctic and wintering in southern Asia. It may be genuinely rare but it is possible a substantial population exists and has been overlooked due to its similarity to A. concinens and A. dumetorum. Its taxonomic status was uncertain for more than a century but was recently confirmed based on morphology and mtDNA evidence (Bensch and Pearson 2002). Given the lack of information, and the previous confusion over the status of this taxon, it is best treated presently as Data Deficient.

Population justification
The global population size has not been quantified, but the species is described as probably extremely rare (del Hoyo et al. 2006).

Trend justification
The current trend is unknown as almost nothing is known of the species's range, movements or ecological requirements.

The 2006 Thailand bird was trapped in area of grassy filter beds at a water treatment site in an area dominated by salt-pans but it is likely this record refers to a vagrant and thus may not be representative of its habitat preferences (Round et al. 2007). The sighting near Kolkata in April 2007 was of a bird feeding in tall bamboo. The likely breeding populations located in north-eastern Afghanistan and in Tajikistan were found in riparian bushland/woodland (Ayé et al. 2010, Timmins et al. 2010).



Conservation Actions Underway
None is known. Conservation Actions Proposed
Examine Acrocephalus museum specimens to search for further examples of the species and to further elucidate its distribution and migration patterns. Obtain photographic evidence and, ideally, DNA from putative individuals. Examine the possibility of stable isotope analysis of any further individuals that are trapped, with the aim of discovering other breeding grounds.

Anon. 2007. Large-billed Reed Warbler rediscovered. World Birdwatch 29(1): 4.

Ayé, R.; Hertwig, S. T.; Schweizer, M. 2010. Discovery of a breeding area of the enigmatic Large-billed Red Warbler Acrocephalus orinus. Journal of Avian Biology 41(4): 452-459.

Bensch, S.; Pearson, D. 2002. The Large-billed Reed Warbler Acrocephalus orinus revisited. Ibis 144: 259-267.

del Hoyo, J.; Elliott, A.; Christie, D. 2006. Handbook of the Birds of the World, vol. 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona, Spain.

Grimmett, R.; Inskipp, C.; Inskipp, T. 1998. Birds of the Indian Subcontinent. Christopher Helm, London.

Pearson, D. J.; Kennerley, P. R.; Bensch, S. 2008. A second museum specimen of Large-billed Reed Warbler Acrocephalus orinus. Bulletin of the British Ornithologists' Club 128(2): 136-138.

Round, P. D.; Hansson, B.; Pearson, D. J.; Kennerley, P. R.; Bensch, S. 2007. Lost and found: the enigmatic Large-billed Reed warbler Acrocephalus orinus rediscovered after 139 years. Journal of Avian Biology 38(2): 133-138.

Round, P. D.; Kennerley, P. R. 2007. Large-billed Reed Warbler Acrocephalus orinus back from the dead. BirdingASIA 7: 53-54.

Svensson, L.; Prys-Jones, R.; Rasmussen, P. C.; Olsson, U. 2008. Discovery of ten new specimens of Large-billed Reed Warbler Acrocephalus orinus, and new insights into its distributional range. Journal of Avian Biology 39(6): 605-610.

Timmins, R. J.; Mostafawi, N.; Rajabi, A. M.; Noori, H.; Ostrowski, S.; Olsson, U.; Svensson, L.; Poole, C. M. 2009. The discovery of Large-billed Reed Warblers Acrocephalus orinus in north-eastern Afghanistan. BirdingASIA 12: 42-45.

Timmins, R. J.; Ostrowski, S.; Mostafawi, N.; Noori, H.; Rajabi, A. M.; Svensson, L.; Olsson, L.; Poole, C. M. 2010. New information on the Large-billed Reed Warbler Acrocephalus orinus, including its song and breeding habitat in north-eastern Afghanistan. Forktail 26: 9-23.

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
Benstead, P., Symes, A., Taylor, J.

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

Recommended citation
BirdLife International (2014) Species factsheet: Acrocephalus orinus. Downloaded from on 28/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from on 28/07/2014.

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.

Key facts
Current IUCN Red List category Data Deficient
Family Sylviidae (Old World warblers)
Species name author Oberholser, 1905
Population size Unknown mature individuals
Population trend Unknown
Distribution size (breeding/resident) 22,400 km2
Country endemic? No
Links to further information
- Additional Information on this species