Data Zone
Justification of Red List category
This species has a moderately large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is unknown, and hence the species cannot be listed as Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is suspected to be moderately small, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Population justification
The species has been described as relatively common at sites where it is known to breed (Timmins et al. 2009, Ayé et al. 2010, Kvartalnov et al. 2013). Recent information from the Wakhan District of Northeastern Afghanistan suggests that the species is found across 450 hectares of suitable habitat that is dispersed across many patches (S. Ostrowski via L. Svensson in litt. 2020). All patches were thought to be occupied, with c. 2-4 breeding pairs per hectare, roughly equating to 900-1,800 breeding pairs across the suitable range in Wakhan (S. Ostrowski via L. Svensson in litt. 2020), converted here to 1,800-3,600 mature individuals. Similarly the species is common in suitable breeding habitat in the Panj, Ghund and lower Pamir valley in Tajikistan (Kvartalnov et al. 2013), suggesting that overall the population is likely to be at least moderately large and likely much greater than 1,000 mature individuals. It is however unknown if the overall breeding range contains similarly high levels of species density (the total breeding range equates to approximately 18,000 km2). Upper limits to the population size are highly uncertain. On a precautionary basis, it is suspected that there are fewer than 10,000 mature individuals, given the relatively restricted breeding area and that only a small fraction of this is suitable habitat. Should further areas with similar densities to those described above exist the true population could well be higher still. Provisionally though the population is placed in a band of 1,000 to 10,000 mature individuals.
Genetic sampling appears to indicate evidence of past barriers within the population but that these have been eroded in relatively recent times, suggesting that there is a level of dispersal sufficient to consider that there is a single population (Svensson et al. 2008, Koblik et al. 2011).
The current population trend is uncertain, but there appear few significant threats to the breeding habitat.
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).
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). In 2014, the species was discovered near a road in the Nal sarovar Bird Sanctuary, near Ahmedebad (Trivedi and Ganpule 2016), and a further sighting has been recorded from the Vansda National Park, Dang, in Gujarat in 2017 (eBird 2021, GBIF.org 2021). Since 2006, there have been further sightings in Thailand, with the individual trapped in 2006 being re-trapped at the same site two 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). The species is however generally considered scarce in Thailand now (W. Limparungpatthanakij in litt. 2022). 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, 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 record in Kazakhstan is from 1926 (Koblik et al. 2011).
The species 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).
The individual trapped in 2006 in Thailand was found 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 (Nimnuan 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 (where in 2021, its habitat was considered to be stable; S. Ostrowski via L. Svensson in litt. 2022) 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 900 and 3,200 m (L. Svensson in litt. 2016, Dyrcz et al. 2020). In winter, the species can also be found in reedbeds, around ponds, canals, rivers, and sewage farms (Dyrcz et al. 2020).
Habitat loss due to the clearance and conversion of riverine areas for agriculture and livestock grazing, coupled with clearance for fuelwood have been suggested as threats to the species within the breeding range (Timmins et al. 2009). However, much habitat remains, especially in the riparian habitats of the Wakhan Corridor where degradation has not been observed for the past five years (S. Ostrowski in litt. via L. Svensson 2022), whilst the impact of livestock and firewood collection on the species is unknown. The habitat used by the species rapidly regrows and it does not depend on intact or forested landscapes. Agricultural and aquacultural intensification in its potential wintering range may also be impacting the species (P. Round in litt. 2017). In Thailand, although there is little information across its non-breeding range, reedbeds where the species has been recorded remain unprotected and are being lost due to conversion into other land-use types (W. Limparungpatthanakij in litt. 2022).
The species is not known to be harvested or face any threat from this across its main breeding range in Afghanistan, although Panjshir Province within the breeding range has been noted as a hotspot for bird capture for food (S. Ostrowski via L. Svensson in litt. 2022). It is unclear whether current trapping efforts may affect the species, with large-bodied birds the main target but passerines are also taken (S. Ostrowski via L. Svensson in litt. 2022).
Conservation Actions Underway
In 2021, the Wildlife Conservation Society afforested 260 hectares along water courses in Wakhan District in Afghanistan, planting poplar, willow, and sea buckthorn trees and scrubs with the aim of recreating diverse riparian ecosystems (S. Ostrowski in litt. via L. Svensson 2022). Further habitat creation is expected to continue in 2022 in the Wakhan, Ishkeshim and Zebak districts (S. Ostrowski in litt. via L. Svensson 2022).
Text account compilers
Martin, R., Fernando, E.
Contributors
Ayé, R., Benstead, P., Das, B., Limparungpatthanakij, W., Mahood, S., Ostrowski, S., Rasmussen, P., Ray, K.S., Round, P., Schweizer, M., Svensson, L., Symes, A., Taylor, J., Westrip, J.R.S. & Wheatley, H.
Recommended citation
BirdLife International (2024) Species factsheet: Large-billed Reed-warbler Acrocephalus orinus. Downloaded from
https://datazone.birdlife.org/species/factsheet/large-billed-reed-warbler-acrocephalus-orinus on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/12/2024.