Blyth's Reed Warbler
Acrocephalus dumetorum
Blyth's reed warbler is between 12 and 14 cm (4.7 and 5.5 in) in length and weighs between 8 and 16 g (0.28 and 0.56 oz). It is a slim warbler with relatively short wings and a long bill. The plumage is rather plain with few distinguishing features and has been described as lacking in "warmer" tones observed in related species. The upperparts are plain olive brown, with less olive on the short, rounded wings. There is a short whitish supercilium running between the base of the bill and the eye, with a dusky stripe through the eye. The underparts are plain and off-white in colour. Voice: Blyth's reed warbler has a variable song in which harsh sounds like ticks, chaks and churrs are mixed in with melodious whistles and mimicry.
ID text from Wikipedia, CC BY-SA 4.0
Marsh Warbler
Acrocephalus palustris
This is a medium-sized warbler. It is very similar in appearance to several other acrocephaline warblers, such as the reed warbler which also occurs in wetlands and has a similar breeding range. The male's distinctive song is useful for identification, as no other member of the genus mimics other birds to any significant extent. The marsh warbler also tends to avoid the stands of pure reed which are the reed warbler's favoured habitat. The sexes are alike in appearance. Hybridisation with both reed warbler and Blyth's reed warbler has been occasionally recorded.
ID text from Wikipedia, CC BY-SA 4.0
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