Large-billed Reed-warbler Acrocephalus orinus


Justification of Red List Category
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.

Population justification
The global population size has not been quantified, but the species has been described as relatively common at sites where it is known to breed (Ayé et al. 2010; Kvartalnov et al. 2013; Timmins et al. 2009).

Trend justification
The current trend is unknown although genetic analysis has demonstrated considerable intra-specific variation from across the range suggesting declining or stable populations (Svensson et al. 2008).

Distribution and population

Acrocephalus orinus was known until relatively recently from only 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) with a further sighting in mangroves in the Sundarbans in West Bengal (K.S. Ray and B. Das in litt. 2009). Since 2006 there have been further sightings in Thailand, with the 2006 bird being re-trapped at the same site 2 years later, and further individuals caught and ringed in other locations in north and central Thailand (Nimnuan and Round 2008, W. Limparungpatthanakij in litt. 2016, P. Round in litt. 2016). An individual was also trapped and ringed in Baikka Beel, Bangladesh in December 2011 (Round et al. 2014). 
Regarding its breeding distribution, it has been established that the species currently breeds in the larger valleys of the western Pamir mountains in both Afghanistan and Tajikistan (Timmins et al. 2009, Ayé et al. 2010, Kvartalnov et al. 2013). Fieldwork conducted in Badakhshan province, north-eastern Afghanistan, located a likely breeding population in 2008-2009 (Timmins et al. 2009, 2010), and in spring 2009, a breeding population was also located in the Badakhshan region of Tajikistan (Ayé et al. 2010). Assessment of museum specimens (mislabeled as Blyth's Reed-warbler A. dumetorum) (Svensson et al. 2008, Koblik et al. 2011) suggest that it may breed from western Afghanistan, Tajikistan, Kyrgyzstan, south and south-west Kazakhstan and adjacent eastern areas of Xinjiang, China. However, recent searches in Chinese valleys close to the Kyrgyzstan and Tajikistan border have so far failed to locate the species (R. Ayé in litt. 2016), and the most recent Kazakhstan record is from 1926 (Koblik et al. 2011). It is 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. Genetic analysis has demonstrated considerable intra-specific variation from across the range suggesting declining or stable populations (Svensson et al. 2008), and the discovery of much of this variation within a relatively small breeding area suggests that there is now a single subpopulation that may have coalesced following the removal of previous geographic barriers (Koblik et al. 2011), e.g. glacial retreat. 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.


The 2006 Thailand bird was trapped in area of grassy filter beds at a water treatment site in an area dominated by salt-pans (Round et al. 2007), while an individual caught at Nam Kham Nature Reserve was found on floodplain in tall grass (Namnuan and Round 2008). The sighting near Kolkata in April 2007 was of a bird feeding in tall bamboo, while there has also been a potential sighting from mangroves (K.S. Ray and B. Das in litt. 2009). The breeding populations located in north-eastern Afghanistan and in Tajikistan were found in mountain valleys in riparian bushland/woodland associated with sea-buckthorn Hippophae rhamnoides and willow Salix spp. (Ayé et al. 2010, Timmins et al. 2010, Kvartalnov et al. 2013). Breeding populations are usually found between 2,000 and 3,200 m, though occasionally will occur to 1,250 m (L. Svensson in litt. 2016).


Habitat loss due to the clearance and conversion of riverine areas for agriculture and livestock grazing, coupled with clearance for fuelwood have been identified as significant threats to the species within the breeding range (Timmins et al. 2009). However, much habitat remains, especially in the Wakhan Corridor and the impact of livestock and firewood collection on the species is unknown. Agricultural and aquacultural intensification in its potential wintering range may also be impacting the species (P. Round in litt. 2017).

Conservation actions

Conservation Actions Underway
None is known.

Conservation Actions Proposed
Examine Acrocephalus museum specimens and conduct ringing surveys in possible Indian and (especially) SE Asian wintering areas 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. Search for breeding areas outside of those already known, potentially into northern Pakistan, central Tajikistan, Kyrgyzstan and Kazakhstan (R. Ayé in litt. 2016, P. Round in litt. 2016). Investigate whether the species is susceptible to overgrazing or other common land use practices in its breeding range (R. Ayé in litt. 2016). Protect the natural alluvial dynamics and riverine woodlands in the western Pamir mountains and adjacent areas (R. Ayé in litt. 2016).


Text account compilers
Martin, R, Wheatley, H., Westrip, J., Benstead, P., Symes, A., Taylor, J.

Schweizer, M., Round, P., Svensson, L., Limparungpatthanakij, W., Rasmussen, P., Das, B., Ray, K., Mahood, S., Ayé, R.

Recommended citation
BirdLife International (2020) Species factsheet: Acrocephalus orinus. Downloaded from http://www.birdlife.org on 08/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 08/08/2020.