European Reed Warblers breed from northwest Africa, across Europe to southern Finland, Russia and western Anatolia. They winter in sub-Saharan Africa from Senegal. east to the Red Sea and south to at least Zambia.
    In Britain at the end of the 19th century they were breeding in much of Wales and in England from Cornwall to Lacashire and Yorkshire. Since then their range has been expanding northwards in increasing numbers: Bird Atlas 2007-2017 recorded little apparent change  in the first half of the 20th century but numbers more than doubling in the last 40 years of the century and increasing by a further 35% between 1995 and 2010.
    In Wiltshire in the first half of the 20th century Reed Warblers were reckoned to be not uncommon though certainly much less common than Sedge Warblers, a difference that persisted to the end of the century. Unsurprisingly, the main concentrations are along the valleys of the Thames, both Avons and the Kennet, plus on the Kennet & Avon Canal and at the CWP and Coate Water. Birds of Wiltshire recorded them in 96 tetrads, with breeding in 58. WTA2 found them in 128 tetrads with breeding in 63.

The following references are used throughout these species’ accounts, in the abbreviated form given in quotation marks:
1968-72 Breeding Atlas” – Sharrack, J.T.R. 1976:  The Atlas of Breeding Birds in Britain and Ireland. T. & A. Poyser
1981-84 Winter Atlas” – Lack, P.C. 1986:  The Atlas of Wintering Birds in Britain and Ireland. T. & A. Poyser
1988-91 Breeding Atlas” – Gibbons, D.W., Reid, J.B. & Chapman, R.A. 1993: The New Atlas of Breeding Birds in Britain and Ireland 1988-91. T. & A. Poyser
“Birds of Wiltshire” – Ferguson-Lees, I.J. et al. 2007: Birds of Wiltshire, published by the tetrad atlas group of the Wiltshire Ornithological Society after mapping fieldwork 1995-2000. Wiltshire Ornithological Society.
Bird Atlas 2007-2011”-– Balmer, D.E., Gillings, S., Caffrey, B.J., Swann, R.L., Downie, I.S. and Fuller, R.J. 2013: The Breeding and Wintering Birds of Britain and Ireland. BTO Books. 
WTA2” – ("Wiltshire Tetrad Atlas 2 ") the present electronic publication, bringing together the Wiltshire data from “Birds of Wiltshire” and “Bird Atlas 2007-11”, together with data from further fieldwork carried out in 2011 and 2012.
"Hobby" - the annual bird report of the Wiltshire Ornithological Society.