Moustached Warbler

The moustached warbler is 12–13 cm (4.7–5.1 in) long, slightly smaller than the similar sedge warbler (Acrocephalus schoenobaenus). The adult has a finely streaked brown back and white underparts. The forehead is flattened, there is a prominent whitish supercilium, grey ear coverts, and the bill is strong and pointed. The sexes are identical, as with most warblers, but young birds are more heavily streaked and have markings on the breast. The song is fast and similar to the sedge warbler and reed warbler, with some mimicry and typically acrocephaline whistles added. Its song is softer and more melodious than those of its relatives, and includes phrases reminiscent of the nightingale. Unlike the sedge warbler, it does not sing in flight.

It is scarce north of its range, but has occurred as a very rare vagrant as far as Poland and Denmark. There have been a few reports from Great Britain, including a pair breeding in Cambridgeshire in 1946, but these records have recently been removed from the official list of British birds, being unconvincingly distinguished from sedge warblers or paddyfield warblers. It is found in upright aquatic vegetation such as reeds and sedge.