USDA National Wildlife Research Center Symposia


Date of this Version

August 2007


Published in: Witmer, G. W., W. C. Pitt, and K. A. Fagerstone, editors. 2007. Managing vertebrate invasive species: proceedings of an international symposium. USDA/APHIS Wildlife Services, National Wildlife Research Center, Fort Collins, Colorado, USA. Also available online at


The ruddy duck (Oxyura jamaicensis) was introduced to wildfowl collections in the United Kingdom (UK) in the 1940s and subsequently escaped into the wild. Estimated numbers have increased rapidly in the UK from 20 wintering birds in 1962 to 5,946 in January 2000. As the population of feral ruddy ducks in the UK rose, so did the number of records of ruddy ducks on the European mainland. In 1984, ruddy ducks were first recorded in Spain, which is home to internationally important populations of the rare indigenous white-headed duck (Oxyura leucocephala). By 1991, hybrids resulting from crosses between the two species were recorded in that country. The two species hybridize readily, with the ruddy duck apparently possessing the competitive advantage. The ruddy duck is now recognized as the most significant threat to the white-headed duck and the UK appears to be the main source of birds reaching mainland Europe. This paper details the development of a control and then an eradication program for this species in the UK.