Archived 2012-2013 topics: Streaked Reed-warbler (Acrocephalus sorghophilus): request for information

This discussion was first published as part of the 2012 Red List update, but remains open for comment to enable reassessment in 2013. BirdLife species factsheet for Streaked Reed-warbler Streaked Reed-warbler Acrocephalus sorghophilus is poorly known and winters in the Philippines, mostly on Luzon, with records also from Negros and Bohol, where it favours reedbeds and tall rank grassland close to water (Kennerley and Pearson 2010). It is thought to breed in north-eastern China (probably in Hebei, Liaoning, Jilin and Heilongjiang provinces) and adjacent areas of Russia, namely the Amur region, where it potentially uses willow scrub and reedbeds (Kennerley and Pearson 2010). It is currently listed as Vulnerable under criterion C2a(ii), on the basis that there are thought to be fewer than 10,000 mature individuals in its population, which is regarded as forming one subpopulation, and is inferred to be in continuing decline owing to on-going habitat destruction, at least in its wintering grounds and probably also in its breeding range. Suitable habitat in the Philippines is threatened by conversion to agricultural land, mainly rice fields, and fishponds, industrial development and human settlement. The conversion of wetlands for agricultural use in north-eastern China may also be contributing to the population decline (Kennerley and Pearson 2010). This species has become less frequent on passage in recent years and concerns have been raised that there may now be fewer than 2,500 mature individuals remaining (D. Allen in litt. 2011). This would qualify the species for uplisting to Endangered under criterion C2a(ii); however, more information is required. Comments are invited on the likely population size and rate of population decline over a period of three generations, estimated by BirdLife to be 13 years (based on an estimated generation length of c.4.4 years). Analyses of trends in the annual number of passage records would be gratefully received, and any other new information on this species would be welcomed. Reference: Kennerley, P. and Pearson, D. (2010) Reed and bush warblers (Helm Identification Guide). London, UK: Christopher Helm.

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2 Responses to Archived 2012-2013 topics: Streaked Reed-warbler (Acrocephalus sorghophilus): request for information

  1. Yang Liu says:

    Only five records were noted in Beijing and Hebei, China during migration seasons over last four years. This species may be overlooked in the field by Chinese birdwatchers since morphological similarity at a distance with other co- migrating small Acrocephalus warblers. Further, because the historical passage records are scant in Mainland China, estimation of trends during the migration seems rather difficult.

  2. Desmond Allen says:
    Justification This poorly known and probably under-recorded warbler qualifies as Vulnerable, as it has a small population, which is declining as a result of wetland destruction in its wintering grounds AND POSSIBLY ITS BREEDING GROUNDS TOO. Its breeding grounds are in urgent need of discovery. IS THERE ANY EVIDENCE THAT THIS SHOULD NOT BE UPLISTED TO CRITICAL? HOW DOES AN ALMOST COMPLETE LACK OF RECORDS COME TO BE ACCEPTED AS AN ALMOST COMPLETE LACK OF BIRDS?
    Taxonomic source(s) Sibley and Monroe (1990, 1993)

    Distribution and population Acrocephalus sorghophilus occurs on passage in Liaoning, Hebei, Hubei, Jiangsu, Fujian and Beijing in eastern China, and Taiwan (China), where there are eight confirmed records3. It winters in the Philippines, where it is local and uncommon, with regular records from Candaba on Luzon and Dalton Pass. NO RECORDS AT DALTON SINCE 1970; VERY FEW AT CANDABA IN RECENT YEARS DESPITE MUCH GREATER LEVEL OF BIRDWATCHING It is presumed to breed in north- east China, possibly in Liaoning and Hebei, and there was a recent record of a singing male at Muraviovka, Russia1, although a subsequent search of the site failed to find any individuals2. There have been less than ten records of birds on passage in the last ten years.
    Population justification Population assumed to be small (<10,000) based on lack of known breeding records in China, and hence presumed small breeding range. WHAT IS THE EVIDENCE THAT THERE ARE MORE THAN 50 BIRDS?
    Trend justification A moderate and continuing population decline is suspected, owing to the paucity of records and on-going habitat destruction in the wintering grounds. NOTWITHSTANDING ID DIFFICULTIES THERE IS A HUGELY INCREASED NUMBER OF BIRDERS AND PHOTOGRAPHERS IN SUITABLE MIGRATION SPOTS IN EASTERN CHINA AND YET ALMOST NONE ARE NOW RECORDED
    Ecology On passage, it has been recorded from millet crops and a marsh and in winter it occurs in reed and grass marsh, often near water. It probably feeds largely on invertebrates and perhaps seeds SEEDS HAVE BEEN REPORTED FROM THE GUT OF A SPECIMEN. THIS NEEDS CONFIRMING AND THE SPECIES NEEDS TO BE IDENTIFIED. Spring passage in China is from late May to early June and autumn passage from late August to early September. All Philippine records are from September to June.
    Threats Habitat destruction on the wintering grounds is likely to be causing a decline. At Candaba, ALMOST ALL marshland has been destroyed through conversion to rice-cultivation, and fishponds. The banks of Laguna de Bay are being occupied by settlers and factories so that the reedbeds are becoming highly fragmented and greatly reduced in area and, at Bukal, Laguna, most reedbed has been drained for conversion to poultry-processing factories. Habitat loss may also be occurring in its breeding grounds.
    Conservation measures underway CMS Appendix II. Candaba Marsh has been proposed as a Ramsar Site and education material has been prepared.
    Conservation measures proposed Attempt to locate the breeding areas in north-east China, particularly using tape-playback. Survey wetlands in the Philippines to try and locate further wintering sites and initiate a new ringing programme at Dalton Pass AMD OTHER MIGRANT TRAPPING SITES. At Candaba, investigate its habitat requirements PROBABLY TOO LATE AS THE SINGLE INDIVIDUALS THER NOW MAY NOT BE IN THEIR PREFERRED OR REQUIRED HABITAT in order to produce conservation recommendations and educational material, designate the site under the National Integrated Protected-Areas System process TOO LATE I WOULD THINK and investigate nearby marshland to see if this should be included under the proposed Ramsar designation. List it as a protected species in China and the Philippines. ALL BIRD SPECIES ARE LEGALLY PROTECTED IN THE PHILIPPINES.

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