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Manchurian Reed-warbler Acrocephalus tangorum

Justification
This species qualifies as Vulnerable because it has a small, declining population as a result of habitat loss in both its breeding and wintering grounds.

Taxonomic source(s)
Alstr

Taxonomic note
Acrocephalus agricola (Sibley and Monroe 1990, 1993) has been split into A. agricola and A. tangorum contra Alstrom et al. (1991) but following Helbig and Seibold (1999).

Identification
13 cm. Small, drab reed-warbler. Uniform tawny-rufous upperparts. Bold, whitish supercilium bordered by dark brow and narrow eye-stripe. White chin, throat and belly becoming buffish-brown on flanks. Similar spp. Paddyfield Warbler A. agricola has less tawny-rufous upperparts and less clearly defined black eyebrow. Black-browed Reed-warbler A. bistrigiceps has more extensive dark crown and more obvious contrast between the black brow and pale centre of crown. Generally duller and more olive-brown upperparts. Voice Typical Acrocephalus song. Calls include a sharp chik-chik, a harsh chr-chuck and a slurred zack-zack.

Distribution and population
Acrocephalus tangorum breeds in south-east Russia and north-east China, and winters in Thailand (mainly at Khao Sam Roi Yot), Cambodia and southern Laos (BirdLife International 2001). It occurs as a scarce passage migrant in Hebei, Liaoning and Hong Kong in China, Pakxan wetlands in Lao (W. Duckworth in litt. 2012) and in Vietnam. The Cambodian population was only discovered recently but appears to be a major stronghold for the species. There are now records from the Northern Plains (Clements et al. 2005), from Mondulkiri Province close to the Vietnam border and from the Tonle Sap floodplain where it is locally common (Bird et al. 2007). The paucity of recent records for well-watched and increasingly heavily monitored and ringed sites (such as Mai Po in Hong Kong and Bung Boraphet in Thailand) suggest it is genuinely very scarce (P. Round in litt. 2012).


Population justification
The global population estimate of 2,500-9,999 mature individuals is based on a detailed analysis of records by BirdLife International (2001), where it was concluded that the species must have a fairly small world population (i.e. fewer than 10,000). This estimate equates to 3,750-14,999 individuals, rounded here to 3,500-15,000 individuals. The population in China has been estimated at 100-100,000 breeding pairs and 50-10,000 individuals on migration (Brazil 2009).

Trend justification
Although perhaps more common than it was thought to be in the 1990s, this species is suspected to be continuing to decline at a moderate rate, owing to the conversion of many natural systems. While it may be tolerant of some modified habitats, the species is unlikely to cope with heavily intensified agricultural and urban environments.

Ecology
In China, it occurs in reedbeds and, in Hong Kong, has been recorded from reeds around overgrown fields and fishponds. At Khao Sam Roi Yot, it is largely confined to Phragmites-dominated reedbeds where it has been recorded at higher densities than any other site (Round and Rumsey 2003, Bird et al. 2007). Recent observations in Cambodia have come from a variety of habitats, particularly tall grass stands (away from water) and sedge beds (both wet and dry), scrub-fringed lotus swamps, and heterogeneous scrub/grass mixes away from water (P. Davidson in litt. 2003). Importantly, the species occurs at similar densities in suitable human modified habitats as it does in natural tall grasslands on the Tonle Sap floodplain (Bird et al. 2007). However, it may be that large expanses of optimal habitat are required to sustain its presence within smaller (possibly suboptimal) habitat patches (P. Round in litt. 2012).

Threats
The main threat on its breeding and wintering grounds is habitat loss, including the loss and degradation of Phragmites marsh in Thailand, such that there is now very little suitable habitat remaining in the entire country. At Khao Sam Roi Yot, freshwater marsh has suffered greatly from encroachment with plantations of casuarinas, eucalyptus and coconut palms, and the establishment of prawn farms with salt and brackish water. This situation is likely to continue. Elsewhere in the country, marshes are threatened by reclamation and urbanisation and no freshwater swamp habitat lies within any protected area. Habitat loss and degradation is continuing at Pakxan wetland, an important stopover site in Lao, where the tall emergent grasses favoured by the species are routinely removed by local people (W. Duckworth in litt. 2012). In Cambodia, the situation may be more promising as the species has been recorded in man-made headponds used for dry season rice cultivation, although its preference for tall dry grass habitat may render it susceptible to dry season burning which is extensive (Bird et al. 2007).

Conservation Actions Underway
CMS Appendix II. Attempts have been made by both international and national conservation organisations to secure the future of Khao Sam Roi Yot. To date these have been unsuccessful. The species was the focus of specific study on the Tonle Sap floodplain, the results of which revealed that it may not be immediately threatened in the area. It may benefit from Integrated Farming and Biodiversity Areas designed to retain semi-natural systems on the Tonle Sap floodplain. Conservation Actions Proposed
Survey suitable habitat in its breeding and wintering ranges to clarify its population size and distribution. Research migration ecology and map stopover sites. Demarcate and protect Khao Sam Roi Yot National Park and formulate and enact a management plan that incorporates ecological objectives with those of local people. Rehabilitate reed-swamps elsewhere in South-East Asia. Encourage Thailand to meet its Ramsar Convention commitments and integrate wetland conservation into land-use planning. Map the existing extent of tall grass habitats in Cambodia with a particular focus on the Tonle Sap inundation zone to enable an order of magnitude population estimate to be generated.

References
Bird, J. P.; Mulligan, B.; Gilroy, J. 2007. Cambodia ornithological expedition 2006.

BirdLife International. 2001. Threatened birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, U.K.

Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

Clements, T.; Davidson, P.; Setha, T. 2005. Where to see: Giant Ibis and White-shouldered Ibis. Northern Plains of Cambodia.

Round, P. D.; Rumsey, S. J. 2003. Habitat use, moult and biometrics in the Manchurian Reed Warbler Acrocephalus tangorum wintering in Thailand. Ringing & Migration 21: 215-221.

Further web sources of information
Detailed species accounts from the Threatened birds of Asia: the BirdLife International Red Data Book (BirdLife International 2001).

Text account compilers
Benstead, P., Bird, J., Peet, N., Taylor, J., Allinson, T

Contributors
Davidson, P., Hornskov, J., Mulligan, B., Round, P., Duckworth, W.

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

Recommended citation
BirdLife International (2014) Species factsheet: Acrocephalus tangorum. Downloaded from http://www.birdlife.org on 12/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 12/07/2014.

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.

Additional resources for this species

ARKive species - Manchurian reed-warbler (Acrocephalus tangorum) 0

Key facts
Current IUCN Red List category Vulnerable
Family Sylviidae (Old World warblers)
Species name author La Touche, 1912
Population size 2500-9999 mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 490,000 km2
Country endemic? No
Links to further information
- Additional Information on this species