Garden Warblers breed from Iberia, France, Italy and Greece north via the British Isles to northern Fenno-Scandia and east to Siberia, and also in northern Turkey, through the Caucasus, to Iran. They winter in sub-Saharan Africa, from Senegal east to Kenya and south to Angola and South Africa.
    In Britain they are widely distributed in summer throughout England and Wales. Once scarce north of a line from the Mersey to the Humber, in recent years they have been expanding northwards  and are now patchily distributed in northern England and lowland areas of Scotland. Bird Atlas 2007-2011 recorded a 12% expansion of range since the 1968-72 Breeding Atlas. Overall numbers remained reasonably stable, apart from a temporary dip in numbers in the 1970s, thought to have been caused by drought in the Sahel, until the 1990s since when there has been a marked decline.
    In Wiltshire they were considered to be "not uncommon" throughout the 19th century and the first half of the 20th century but reports began to sound a more pessimistic note towards the end of the latter century: BBS survey reports showed a 16% fall in numbers between 1995 and 2010; Birds of Wiltshire recorded their presence in 433 tetrads, with breeding confirmed or probable in 172 of them; WTA2 recorded them in 382 tetrads, with breeding only in 89.
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.