Clamorous reed-warbler (Acrocephalus stentoreus)

Also known as: Assam great reed-warbler, Ceylon great reed-warbler, clamorous reed warbler, Heinroth’s reed-warbler, Indian great reed-warbler, southern great reed-warbler, Sri Lanka great reed-warbler
GenusAcrocephalus (1)
SizeLength: 18 - 20 cm (2)
Weight23 - 24 g (2)

Classified as Least Concern (LC) on the IUCN Red List (1).

A rather plain, inconspicuous warbler more often heard than seen, the clamorous reed-warbler is a skulking bird that stays out of sight in dense vegetation. A well camouflaged bird, the upperparts are plain olive-brown, with a conspicuous white stripe through each eye and a reddish tinge to the rump. The flight and tail feathers are dark brown with whitish edges and the underparts are suffused with white, often with a few dark streaks on the chin and throat (2) (3). The sexes are similar, but the juvenile has a more rusty-brown appearance to the upperparts. The bill is long and stout and the long, rounded tail acts as a balancing aid as the bird weaves its way through dense vegetation (3) (4). The clamorous reed-warbler may be distinguished from other reed-warblers by its slenderer build, slightly longer tail, thinner bill, shorter wings and narrower eye stripe. It is, however, more renowned for its very loud song, which combines harsh grating and chattering sounds with more melodic notes and squeaks. It also often mimics the calls of other birds (2).

The clamorous reed-warbler has a very large range stretching from Northeast Africa and the Arabian Peninsula, through South and Southeast Asia to the Philippines, New Guinea and Australia (1) (2) (5). Most populations remain fairly sedentary year-round, but the most northerly populations tend to migrate southwards before the onset of winter to spend the colder months in the Indian subcontinent (2) (3).

A fairly inconspicuous bird when not singing, the clamorous reeed-warbler is usually found foraging around thorn trees, bushes, reed and papyrus stands and other tall wetland vegetation along stream beds, marshes, irrigations ditches, mangroves and lakes (2) (3). In Australia it is resident around permanent lakes, and in Nepal it is found among ferns in ricefields during the winter (3) (5). It occurs up to an altitude of around 3,000 metres in the Himalayas (2).

Foraging out of sight near the ground or water level, the clamorous reed-warbler feeds on a variety of prey, including dragonflies, water beetles, grasshoppers and spiders (3). Insects are gleaned off vegetation within reed stands and bushes, and prey may also be taken from the water surface, from floating vegetation, or from the ground when the bird hops about in marshy areas (2).

The clamorous reed-warbler has an unusual method of breeding as pairs may form monogamous relationships or the male bird may attempt to father the offspring of several females (2). The female does most of the nest building, constructing an intricate, deep, cup-shaped nest out of reeds which is placed above water in dense vegetation. Between three and five eggs are laid and incubated by the female (2) (3). The chicks remain in the nest for 11 to 13 days, during which time they are tended to by both parent birds (2).

As the clamorous reed warbler has a very large range and is believed to be common in most countries, with tens of thousands of pairs in the Nile Delta alone, it is not thought to be threatened with extinction. There are also no known major threats to the species (2) (6). It is, however, thought to be fairly uncommon in Myanmar and the Philippines (6).  

In the absence of any major threats to the species’ survival, the clamorous reed-warbler has not been the target of any known specific conservation measures (6).

To find out more about the conservation of birds, see:

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  1. IUCN Red List (September, 2010)
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (2006) Handbook of the Birds of the World. Volume 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona.
  3. Kumar Shrestha, T.  (2001) Birds of Nepal: Field Ecology, Natural History and Conservation. R.K. Printers, Kathmandu, Nepal.
  4. Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
  5. Wooller, S.J. and Wooller, R.D. (1997) Overwintering by clamorous reed-warblers Acrocephalus stentoreus in Perth, western Australia. Emu, 97: 332-334.
  6. BirdLife International (September, 2010)