Originally described from a single specimen collected in the Sutlej Valley near Rampoor, Himachal Pradesh, India in 1867, this species was long the subject of various theories as to whether it was a separate species or simply a hybrid or variant of some other species. However, a thorough investigation of the only known specimen carried out in 2002 proved that it was indeed a separate species based on its morphology and mitochondrial DNA.
Since then the first ever live specimen has been trapped in March 2006 in Thailand, and another specimen (collected in October 1869 at Mussourie, Uttarakhand, India) has been discovered among the collection of Blyth's Reed Warbler Acrocephalus dumetorum skins at the Natural History Museum at Tring in the UK.
Bensch, S. and Pearson, D. (2002) The Large-billed Reed Warbler Acrocephalus orinus revisited. Ibis 144: 259-267.
Philip D. Round, Bengt Hansson, David J. Pearson, Peter R. Kennerley, Staffan Bensch. (2007) Lost and found: the enigmatic large-billed reed warbler Acrocephalus orinus rediscovered after 139 years. Journal of Avian Biology 38:2 133