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Gadwalls were scarce in Great Britain until the mid 19th century when released specimens combined with the rare wild stock to establish a local breeding population in East Anglia. From there the species eventually spread to other parts of Britain, slowly at first but then rapidly in the two decades between the 1968-72 Breeding Atlas and the 1988-91 BreedingAtlas. This expansion has continued: the annual Breeding Bird Survey revealed an increase in the UK breeding population of 83% between 1995 and 2010, while wintering numbers are estimated to have increased more than threefold between 1983-84 and 2008-09 making it the fastest growing wildfowl population apart from introduced Greylag Geese.
    Gadwalls did not reach Wiltshire in significant numbers until the mid 1960s when double figure winter counts began to be regularly recorded at Fonthill Lake, with smaller numbers appearing at other sites. Fonthill subsequently declined in importance, though other sites, notably the Cotwold Water Park, saw rapid increases and overall the Wiltshire picture matched the national pattern of fast growth from the 1970s onwards.
    The first recorded breeding attempt in Wiltshire occurred at Clarendon Lake in 1984 though it was not until the 1990s that breeding began to be recorded with any regularity in the county. Birds of Wiltshire recorded probable or confirmed breeding at Coate Water, in four tetrads along the River Kennet, at Langford Lakes and Clarendon Lake, and presence in a further 19 tetrads. At the time it was estimated that there were probably 10-20 pairs breeding annually in the county. Bird Atlas 2007-2011 recorded the presence of Gadwalls in 49 Wiltshire tetrads with probable or confirmed breeding in 29 of them, and a breeding population of at least 75 pairs.

 

References
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.


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