Small and restless species easily confused with Sedge Warbler, Acrocephalus schoenobaenus, but showing both plumage and structural differences. Plumage differs from A. schoenobaenus in; broad, white supercilium ending without narrowing, dark crown (usually appears black), pure white throat, grey ear-coverts, dark legs and warm-rufous flanks, rump and neck. Facial markings recalling firecrest. Very short primary projection and longer, more evenly rounded tail recalling Wren when raised. Bill thinner than A. schoenobaenus. Skulky behaviour, forages low in vegetation, on ground or near water surface. Some variation in both size and plumage between western and eastern subspecies.

Contact call a dry "trrrt", similar to corresponding call of Sedge Warbler. Song most resembling that of Reed Warbler (A, scirpaceus), but often includes diagnostic (unique among congeners), pure-sounding note sequence resembling crescendo of Common Nightingale (L. megarhynchos), before launching into typical Acrocephalus sounding song. This latter type can be sustained for some time without the diagnostic sequence and is more difficult to distinguish from A. scirpaceus. Note faster tempo and more variation.

Diagnostic song:

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CC-photo:Radovan Václav, Licence,Link.

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