UPPERCASE: current genusUppercase first letter: generic synonym● and ● See: generic homonymslowercase: species and subspecies●: early names, variants, misspellings‡: extinct†: type speciesGr.: ancient GreekL.: Latin<: derived fromsyn: synonym of/: separates historical and modern geographic namesex: based onTL: type localityOD: original diagnosis (genus) or original description (species)
13–14 cm; 10·9 g (n = 1) (1
Round, P.D., Ul Haque, E., Dymond, N., Pierce, A.J. and Thompson, P.M. (2014). Ringing and ornithological exploration in north-east Bangladesh wetlands. Forktail. 30: 109–121.
). Medium-sized reed-warbler with noticeably large and strong bill, long narrow tail with pointed feathers, rounded wingtip. Has pale superciliary stripe not strongly pronounced; upperparts rich olive-brown, slight rufous tinge (especially on uppertail-coverts and edgings to greater coverts); throat creamy olive, underparts strongly washed olive-buff, sides more olive-brown; iris dark; maxilla dark with pale cutting edges, entire mandible pale; legs, toes and claws pale brown. Differs from A. dumetorum mainly in slightly longer bill, legs and claws, with maxilla typically being uniformly dark and the hind claws quite pointed (2
Svensson, L., Prys-Jones, R., Rasmussen, P.C. and Olsson, U. (2010). The identification and distribution of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Ibis. 152: 323–334.
). Sexes presumably similar. Juvenile warmer brown and more rufous-tinged overall than adult, with maxilla slightly paler and more reddish brown (2
Svensson, L., Prys-Jones, R., Rasmussen, P.C. and Olsson, U. (2010). The identification and distribution of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Ibis. 152: 323–334.
).
Systematics History
Until recently known only from type specimen, which had been variously suggested to represent an isolated population of A. stentoreus, a hybrid with A. dumetorum, or an aberrant A. dumetorum. However, re-examination of its morphology and mitochondrial DNA supports treatment as a separate species (3
Bensch, S. and Pearson, D. (2002). The Large-billed Reed Warbler Acrocephalus orinus revisited. Ibis 144(2): 259–267.
). Subsequently, three individuals were captured in Thailand in 2006–2008 (4
Nimnuan, S. and Round, P.D. (2008). Further Thai records of large-billed reed warblers Acrocephalus orinus. BirdingASIA 9: 10.
) and at least 27 specimens have been discovered in museums, erroneously labelled as A. dumetorum (5
Svensson, L., Prŷs-Jones, R., Rasmussen, P.C. and Olsson, U. (2010). The identification and distribution of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Ibis 152(2): 323–334.
, 6
Koblik, E.A., Red’kin, Y.A., Meer, M.S., Derelle, R., Golenkina, S.A., Kondrashov, F.A. and Arkhipov, V.Y. (2011). Acrocephalus orinus: a case of mistaken identity. PLoS ONE 6(4): e17716.
). Monotypic.
Subspecies
Monotypic.
Distribution
Breeding range apparently extends from SE Kazakhstan to NE Afghanistan, through Tajikistan and parts of E Uzbekistan and Kyrgyzstan, in mountainous areas at 900–3000 m (7
Timmins, R.J., Mostafawi, N., Rajabi, A.M., Noori, H., Ostrowski, S., Olsson, U., Svensson, L. and Poole, C.M. (2009). The discovery of Long-billed Reed Warblers Acrocephalus orinus in north-eastern Afghanistan. BirdingASIA 12: 42–45.
, 8
Ayé, R., Hertwig, S.T. and Schweizer, M. (2011). Discovery of a breeding area of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. J. Avian Biol. 41(5): 452–459.
, 6
Koblik, E.A., Red’kin, Y.A., Meer, M.S., Derelle, R., Golenkina, S.A., Kondrashov, F.A. and Arkhipov, V.Y. (2011). Acrocephalus orinus: a case of mistaken identity. PLoS ONE 6(4): e17716.
). Wintering grounds not established but recorded in N India, Myanmar and Thailand (5
Svensson, L., Prŷs-Jones, R., Rasmussen, P.C. and Olsson, U. (2010). The identification and distribution of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Ibis 152(2): 323–334.
).
Habitat
Breeds in thickets of sea-buckthorn (Hippophae rhamnoides) and willows (Salix spp.), near river banks, canals and other wet areas in alluvial plains or mountain valleys (9
Timmins, R.J., Mostafawi, N., Rajabi, A.M., Noori, H., Ostrowski, S., Olsson, U., Svensson, L. and Poole, C.M. (2009). The discovery of Long-billed Reed Warblers Acrocephalus orinus in north-eastern Afghanistan. BirdingASIA. 12: 42–45.
, 10
Ayé, R., Hertwig, S.T. and Schweizer, M. (2010). Discovery of a breeding area of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Journal of Avian Biology. 41(4): 452–459.
) (11
Kvartalnov, P., Abdulnazarov, A., Samotskaya, V., Poznyakova, J., Ilyina, I., Bannikova, A. and Solovyeva, E. (2013). Nesting of the Large-billed Reed Warbler Acrocephalus orinus: a preliminary report. Forktail. 29: 37–42.
). Found in winter in reedbeds or other lush vegetation, including Ipomoea fistulosa (1
Round, P.D., Ul Haque, E., Dymond, N., Pierce, A.J. and Thompson, P.M. (2014). Ringing and ornithological exploration in north-east Bangladesh wetlands. Forktail. 30: 109–121.
), around ponds, canals, rivers and sewage farms (2
Svensson, L., Prys-Jones, R., Rasmussen, P.C. and Olsson, U. (2010). The identification and distribution of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Ibis. 152: 323–334.
).
Movement
Summer visitor to Central Asia, noted in Tajikistan from late May to Sept (11
Kvartalnov, P., Abdulnazarov, A., Samotskaya, V., Poznyakova, J., Ilyina, I., Bannikova, A. and Solovyeva, E. (2013). Nesting of the Large-billed Reed Warbler Acrocephalus orinus: a preliminary report. Forktail. 29: 37–42.
). Recorded in N Pakistan in late Aug, in N India in Oct, Nov and May, in Thailand in Mar, Bangladesh in Dec (1
Round, P.D., Ul Haque, E., Dymond, N., Pierce, A.J. and Thompson, P.M. (2014). Ringing and ornithological exploration in north-east Bangladesh wetlands. Forktail. 30: 109–121.
) and in Myanmar in early May (2
Svensson, L., Prys-Jones, R., Rasmussen, P.C. and Olsson, U. (2010). The identification and distribution of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Ibis. 152: 323–334.
).
Diet and Foraging
No information.
Sounds and Vocal Behavior
Song similar to Blyth’s Reed Warbler (9
Timmins, R.J., Mostafawi, N., Rajabi, A.M., Noori, H., Ostrowski, S., Olsson, U., Svensson, L. and Poole, C.M. (2009). The discovery of Long-billed Reed Warblers Acrocephalus orinus in north-eastern Afghanistan. BirdingASIA. 12: 42–45.
).
Breeding
The sole existing study was conducted in S Tajikistan (11
Kvartalnov, P., Abdulnazarov, A., Samotskaya, V., Poznyakova, J., Ilyina, I., Bannikova, A. and Solovyeva, E. (2013). Nesting of the Large-billed Reed Warbler Acrocephalus orinus: a preliminary report. Forktail. 29: 37–42.
). Monogamous, although attempted extra-pair copulations observed. Nest constructed by female, attached to sea-buckthorn twigs or to stems of Artemisia, liquorice (Glycyrrhiza uralensis), willows, reeds etc., 1·1–2·1 m up over dry ground. Clutch 2–5 eggs, mean 3·77 (n = 13). Eggs dirty white, rarely creamy or pure white, with dark spots and specks, size c. 17·7 mm × 13·1 mm, mass c. 1·5 g. Both sexes incubate and feed nestlings and fledglings. Most nestbuilding in June; fledglings recorded late Jun to Jul.
Data Deficient. Until very recently known only from the type specimen, collected in the Sutlej Valley, near Rampur, Himachal Pradesh, N India, in Nov 1867. In Mar 2006, one was trapped at a sewage farm in Laem Phak Bia, SC Thailand (12
Round, P.D., Hansson, B., Pearson, D.J., Kennerley, P.R. and Bensch, S. (2007). Lost and found: the enigmatic Long-billed Reed Warbler Acrocephalus orinus rediscovered after 139 years. Journal of Avian Biology. 38: 133–138.
), and re-trapped in Mar 2008 (13
Nimnuan, S. and Round, P. (2008). Further Thai records of Large-billed Reed Warblers Acrocephalus orinus. BirdingASIA. 9: 10.
), while another live bird trapped in Mar 2008 in Chiang Rai province, N Thailand (13
Nimnuan, S. and Round, P. (2008). Further Thai records of Large-billed Reed Warblers Acrocephalus orinus. BirdingASIA. 9: 10.
); DNA tests confirmed their identity, as was also true for a recent winter record in NE Bangladesh (Dec 2011) (1
Round, P.D., Ul Haque, E., Dymond, N., Pierce, A.J. and Thompson, P.M. (2014). Ringing and ornithological exploration in north-east Bangladesh wetlands. Forktail. 30: 109–121.
). Additional museum specimens, erroneously labelled as A. dumetorum were discovered soon after the Thai records were made (14
Pearson, D.J., Kennerley, P.R. and Bensch, S. (2008). A second museum specimen of Large-billed Reed Warbler Acrocephalus orinus. Bull. Brit. Orn. Club. 128: 136–137.
, 15
Svensson, L., Prys-Jones, R., Rasmussen, P.C. and 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: 605–610.
, 16
Koblik, E.A., Red’kin, Y.A., Meer, M.S., Derelle, R., Golenkina, S.A., Kondrashov, F. A. and Arkhipov, V.Y. (2011). Acrocephalus orinus: a case of mistaken identity. PLOS One. 6(4): e17716. doi:10.1371/journal.pone.0017716.
). In 2009 several individuals were found in apparently suitable breeding habitat in Zebak and the nearby Wakhan Valley, N Afghanistan (9
Timmins, R.J., Mostafawi, N., Rajabi, A.M., Noori, H., Ostrowski, S., Olsson, U., Svensson, L. and Poole, C.M. (2009). The discovery of Long-billed Reed Warblers Acrocephalus orinus in north-eastern Afghanistan. BirdingASIA. 12: 42–45.
), and a bird was seen feeding fledglings in SE Tajikistan (10
Ayé, R., Hertwig, S.T. and Schweizer, M. (2010). Discovery of a breeding area of the enigmatic Large-billed Reed Warbler Acrocephalus orinus. Journal of Avian Biology. 41(4): 452–459.
). In 2011–2012 the species was found to be common in suitable habitat in the Panj, Ghund and lower Pamir Valleys, Tajikistan (11
Kvartalnov, P., Abdulnazarov, A., Samotskaya, V., Poznyakova, J., Ilyina, I., Bannikova, A. and Solovyeva, E. (2013). Nesting of the Large-billed Reed Warbler Acrocephalus orinus: a preliminary report. Forktail. 29: 37–42.
). More information, however, is needed to assess its conservation status.
Dyrcz, A., E. de Juana, and G. M. Kirwan (2020). Large-billed Reed Warbler (Acrocephalus orinus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.labrew1.01
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