The large-billed reed warbler is an Old World warbler in the genus Acrocephalus. The species has been dubbed as "the world's least known bird". It was known from a single specimen collected in India in 1867 and rediscovered in the wild in Thailand in 2006. The identity of the bird caught in Thailand was established by matching DNA sequences extracted from feathers; the bird was released. After the rediscovery in the wild a second specimen was discovered amid Acrocephalus dumetorum specimens in the collections of the Natural History Museum at Tring. A breeding area was found in Afghanistan in 2009 and studies in 2011 pointed to its breeding in Kazakhstan and Tajikistan. One bird was found in the Baikka Wetland in Srimangal, Bangladesh on 7 December 2011.
Region
Central and South Asia
Typical Environment
Breeds in riparian and marshy habitats across parts of Central Asia, including river valleys with dense grasses, reeds, and willow or tamarisk scrub. During migration and in winter it uses lowland wetlands, reedbeds, damp grasslands, and shrubby river edges in South Asia. It favors dense cover and often keeps low within vegetation, making it hard to observe. Wintering and passage records come from countries such as India, Bangladesh, and Thailand. Because of its similarity to related warblers, it is likely under-recorded.
Altitude Range
Sea level to 1800 m
Climate Zone
Continental
Ease of Keeping
Beginner friendly: 1/5
Long known from a single 1867 Indian specimen, the species was rediscovered in Thailand in 2006 using DNA from a released bird, earning it a reputation as one of the world’s least-known birds. Breeding sites were later found in Afghanistan, with further evidence pointing to breeding in Kazakhstan and Tajikistan and wintering in South Asia. It closely resembles Blyth’s reed warbler, and careful measurements and DNA are often needed to confirm identification. Its secretive habits in dense vegetation likely explain its elusiveness.
Primary tip shape
Temperament
secretive and skulking
Flight Pattern
short rapid wingbeats, low over vegetation
Social Behavior
Breeds in pairs in dense riparian vegetation, with nests placed low in reeds or shrubs. Outside the breeding season it is typically solitary or in loose association with other small passerines using the same habitat. It is highly inconspicuous, often moving quietly within thick cover and rarely perching in the open.
Migratory Pattern
Seasonal migrant
Song Description
A rapid, chattering warble with varied phrases and mimicry, delivered from within cover. Softer and less forceful than some congeners, with intermittent pauses. Calls are thin and ticking, easily overlooked among other reed warblers.
Plumage
Plain brown upperparts with slightly warmer rump, pale buffy underparts, and a subtly streak-free appearance; texture smooth and sleek. A faint, pale supercilium and relatively long tail give a somewhat elongated look. The bill is notably long and heavy-based for a reed warbler.
Diet
Primarily consumes small insects such as flies, beetles, and moths, along with their larvae. It also takes spiders and other small invertebrates gleaned from stems and leaves. Forages by picking prey from reed stems and low shrubs, occasionally making short sallies to catch flying insects. Seasonal prey composition likely varies with availability in breeding and wintering areas.
Preferred Environment
Feeds within dense reedbeds, sedge beds, and shrubby river margins, usually close to water. Often keeps low in vegetation, using cover to move and forage unobtrusively. During migration and winter, frequents wet meadows and marsh edges with thick grass or reed growth.
