Great Black-backed Gulls are confined to the north Atlantic region, breeding from Greenland, Iceland, Svalbard and Novaya Zemlya, south to Ireland, western Great Britain, northwest France, Fenno-Scandia and, in north America, from Quebec to New England. In winter they disperse south as far as western Iberia, the Azores and Florida.
    In Great Britain they breed almost exclusively in coastal areas, with 85% of the population found in Scotland, while most of the rest are scattered around the Welsh coast and the southwest peninsula and the south coast of England. Non-breeding individuals in summer and over-wintering birds occur widely on coasts but also inland except in highland areas.
    Great Black-backed Gulls were rare in Wiltshire until the mid 20th century when they began to appear more regularly, usually singly but occasionally in groups of between three and six and in one instance as many as 16 on a rubbish tip in January 1993. Although they have been recorded in the county in every month of the year, summer records are rare and there have been no records of breeding attempts. Birds of Wiltshire reported records in winter annually from the Cotswold Water Park (CWP) and from sites in Swindon as well as from one to three sites elsewhere in the county although the partial tetrad survey carried out over two winters between 1998 and 2000 produced records from only one tetrad, near the CWP. By contrast, WTA2 has winter records from 29 tetrads.


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.