A common breeder around the estuaries and coastal marshes of the British Isles, the most striking national change revealed by Bird Atlas 2007- 2011 was the increasing colonisation of inland sites, during both winter and the breeding season. Despite these range increases the national population trends show a slight decline in winter numbers since the mid-1990s, and although the breeding population is estimated to have increased by 2% in the same period this is lower than might have been expected given the range expansion.
    The increasing colonisation of inland sites shows up in the Wiltshire figures. Until the 1960s there were only occasional winter records of the species in the county. From then onwards winter records became more regular, particularly at the Cotswold Water Park (CWP) where there have been double figure counts in many years since 1997 with a maximum of 18 in March 2000 and again in March 2010. Summer records were rare until the 1980s but since then have become regular. Breeding was first recorded at the CWP in 1990 and has occurred there in at least ten years since. There have also been records of successful breeding at Charlton-All-Saints in 2007 and of probable breeding at Coate Water in 2008, 2009 and 2010.
    In Birds of Wiltshire confirmed or probable breeding was recorded in only one tetrad and presence in six others; in  Bird Atlas 2007- 2011 confirmed or probable breeding was recorded in eight tetrads and presence in six others. Detailed winter statistics are not available for comparison but such figures as are available suggest a fairly stable situation between the 1980s, when the 1981-84 Winter Atlas recorded the species in nine 10km squares, and 2007-11 when it was recorded from ten 10km squares.


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.