Rooks breed aross Eurasia from western and central Europe, through southern Siberia, Asia Minor and northern Iran to central and northeast China and the lower reaches of the Amus and Ussuri rivers. Thry have been introduced in New Zealand. In the northerly parts of their range they  migrate in winter, but elsewhere including in Britain they are largely sedentary. In Europe numbers fluctuated during the 20th century as a result of agricultural changes, chemical poisoning and persecution, but have now stabilised and are increasing in the west.
In Britain they are absent only from the barer uplands of Scotland, Wales and northern England and from large urban areas. Numbers rose in the last quarter of the 20th century, but have since declined and most of the increase has since been reversed: while a national Rook survey in 1996 indicated a 40% population increase since 1975, the 2018 report of the Breeding Bird Survey recorded a 23% reduction in the UK population between 1995 and 2017. Bird Atlas 2007-2011 showed only marginal change since the 1968-72 Breeding Atlas.
In Wiltshire, where Rooks have always been regarded as very abundant, the population changed in line with the national trend in the latter part of the 20th century - a 41% increase in the number of nests was recorded between 1975 and the end of the century. However the decrease recorded nationally since 1995 does not appear to be reflected in the local figures, which show no significant change between Birds of Wiltshire and WTA2.

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: Bird Atlas 2007-2011: the Breeding and Wintering Birds of Britain and Ireland
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.