This Reed Warbler is raising the young of a Common Cuckoo

The Acrocephalus warblers are small, insectivorous passerine birds belonging to the genus Acrocephalus. Formerly in the paraphyletic Old World warbler assemblage, they are now separated as the namesake of the marsh- and tree-warbler family Acrocephalidae. They are sometimes called marsh-warblers or reed-warblers, but this invites confusion with Marsh Warbler and Reed Warbler proper, especially in North America where it is common to use lower case for bird species.

These are rather drab brownish warblers usually associated with marshes or other wetlands. Some are streaked, others plain. Many species are migratory.

Many species have a flat head profile, which gives rise to the group's scientific name.

Species breeding in temperate regions are strongly migratory.

The most enigmatic species of the genus, the Large-billed Reed-warbler (Acrocephalus orinus), was rediscovered in Thailand on March, 2006. It was only found once before, in 1867.

List of species in taxonomic order

• Moustached Warbler, Acrocephalus melanopogon
• Aquatic Warbler, Acrocephalus paludicola
• Sedge Warbler, Acrocephalus schoenobaenus
• Streaked Reed-warbler, Acrocephalus sorghophilus
• Black-browed Reed-warbler, Acrocephalus bistrigiceps
• Paddyfield Warbler, Acrocephalus agricola
• Manchurian Reed-warbler, Acrocephalus tangorum
• Blunt-winged Warbler, Acrocephalus concinens
• Eurasian Reed Warbler, Acrocephalus scirpaceus
  • Caspian Reed Warbler, Acrocephalus (scirpaceus) fuscus
  • Mangrove Reed Warbler, Acrocephalus (scirpaceus) avicenniae
• African Reed Warbler, Acrocephalus baeticatus
• Blyth's Reed Warbler, Acrocephalus dumetorum
• Marsh Warbler, Acrocephalus palustris
• Great Reed-warbler, Acrocephalus arundinaceus
• Oriental Reed-warbler, Acrocephalus orientalis
• Clamorous Reed-warbler, Acrocephalus stentoreus
• Large-billed Reed-warbler, Acrocephalus orinus
• Basra Reed-warbler, Acrocephalus griseldis
• Australian Reed-warbler, Acrocephalus australis
• Nightingale Reed-warbler, Acrocephalus luscinia
  • Aguiguan Nightingale Reed-warbler, Acrocephalus luscinia nijoi "? doubtfully distinct; extinct (c.1997)
  • Astrolabe Nightingale Reed-warbler, Acrocephalus luscinia astrolabii "? extinct (mid-19th century?)
  • Pagan Nightingale Reed-warbler, Acrocephalus luscinia yamashinae "? doubtfully distinct; extinct (1970s)
• Caroline Reed-warbler, Acrocephalus syrinx
• Nauru Reed-warbler, Acrocephalus rehsei
  • Marshall Islands Reed-warbler, Acrocephalus rehsei ssp.? "? hypothetical; extinct (c.1880?)
• Millerbird, Acrocephalus familiaris
  • Nihoa Millerbird, Acrocephalus familiaris kingi
  • Laysan Millerbird, Acrocephalus familiaris familiaris "? extinct (late 1910s)
• Christmas Island Warbler, Acrocephalus aequinoctialis
• Tahiti Reed-warbler, Acrocephalus caffer
  • Huahine Reed-warbler, Acrocephalus caffer garretti "? extinct (19th century?), renamed in Acrocephalus musae garretti
  • Raiatea Reed-warbler, Acrocephalus caffer musae "? extinct (19th century?), renamed in Acrocephalus musae musae
• Moorea Reed-warbler, Acrocephalus longirostris "? extinct (1980s?) (split from Acrocephalus caffer in 2008)
• Tuamotu Reed-warbler, Acrocephalus atyphus
• Rimatara Reed-warbler, Acrocephalus rimatarae
• Pitcairn Reed-warbler, Acrocephalus vaughani
• Henderson Island Reed-warbler, Acrocephalus taiti
• Marquesan Reed-warbler, Acrocephalus mendanae
• Cook Islands Reed-warbler, Acrocephalus kerearako
• Greater Swamp-warbler, Acrocephalus rufescens
• Cape Verde Swamp-warbler, Acrocephalus brevipennis
• Lesser Swamp-warbler, Acrocephalus gracilirostris
• Madagascar Swamp-warbler, Acrocephalus newtoni
• Thick-billed Warbler, Acrocephalus aedon
• Rodrigues Brush-warbler, Acrocephalus rodericanus
• Seychelles Warbler, Acrocephalus sechellensis

Fragmentary fossil remains from the Late Miocene (about 11 mya) of Rudabánya (NE Hungary) show some apomorphies typical of this genus (Bernor et al. 2002). Given its rather early age (most Passerida genera are not known until the Pliocene), it is not too certain that it is correctly placed here, but it is highly likely to belong to the Acrocephalidae at the least.

Notes

1. ^ a b c Cibois, Thiboult & Pasquet: Systematics of the extinct reed warblers Acrocephalus of the Society Islands of eastern Polynesia. Ibis (2008), 150, 365"?376