Abundant throughout the northern hemisphere, from the Arctic to the subtropics, and widely introduced elsewhere, Mallards are the common ancestors of most domesticated ducks, which has led to a good deal of interbreeding between escaped and wild ducks and to the establishment of naturalised populations outside their natural range. Large numbers are also bred and released for shooting which further complicates attempts to estimate population trends.
    In Great Britain numbers declined sharply following the widespread drainage of wetlands and improvements in wildfowlers’ firearms from the 18th century onwards. It was only when various wildlife protection acts, for example banning shooting during the breeding season, began to take effect at the beginning of the 20th century that numbers started to increase again until by the end of that century the species was ubiquitous and numbering in the hundreds of thousands. The resident population is augmented in winter by migrants from northern Europe. A recent marked decrease in winter numbers is suspected to have been the result of warmer winters causing fewer continental birds to migrate westwards.
    In Wiltshire Mallards were regarded as a familiar species in the 19th century but mostly as winter visitors. In the 20th century the county’s resident breeding population built up in line with the national trend, reaching an estimated 1500-2000 pairs by the end of the century (Birds of Wiltshire). By then they were to be found wherever suitable habitat was available, from small ponds to major lakes and rivers, giving little scope for further range expansion: they were recorded in 532 tetrads in Birds of Wiltshire and in 526 in Bird Atlas 2007-2011. There was however some increase in productivity over the decade (again reflecting the national trend) with confirmed or probable breeding recorded in 353 tetrads compared with 299 tetrads ten years previously.


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.