Native of an area stretching from south Canada to Central America and the Caribbean, Ruddy Ducks were first introduced to collections in Europe in 1936. Two pairs were brought to Slimbridge in 1948, where they readily bred. By 1963 some 70 unpinioned juveniles had escaped into the wild, establishing successful naturalised populations, initially in Chew Valley Lake in Somerset and the West Midlands, then spreading to other parts of England, Wales and Scotland. The 1988-91 Breeding Atlas estimated the population at 570 pairs. By the winter of 1999-2000, Wetland Bird Survey counts were showing a British count of 4565 and the UK population is estimated to have peaked at around 6000 in 2000.
    Meantime, the species had spread to 19 other European and North African countries including Spain, where it hybridised with the local population of the globally endangered White-headed Duck Oxyura leucocephala. Because of this threat of genetic swamping of an endangered species a control and subsequent eradication programme was launched, which in Britain led to a 90% reduction by 2009 and to possibly no more than 60 individuals in 2012.
    Ruddy Ducks first appeared in Wiltshire in the late 1960s, but it was not until 1976 that they started to appear annually in gradually increasing numbers. They first bred in the county at Tockenham Reservoir in 1977, though it was 11 years before they were again recorded breeding, at Langford Lakes, in August 1988. From 1990 until 2001, they bred every year, often in two or three different sites. After a hiatus in 2002, they were again recorded breeding for four more years until 2006 when they bred at Coate Water, Corsham and the Cotswold Water Park (CWP). There have been no further breeding records since then. Numbers wintering in the county built up to a maximum of 112 at six separate sites in December 2003. Thereafter numbers began to decline as the eradication programme kicked in, falling to 63 at seven sites in 2005, 33 at six sites in 2006, 12 at three sites in 2009, six at a single site (CWP) in 2012 and finally to just one lingering on at the CWP in 2015.


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.