The ruddy duck is a small, stiff-tailed duck native to North America. However, in recent decades it has been introduced to Europe and become an invasive species in the United Kingdom. This has raised concerns about the ruddy duck’s negative impacts on the endangered white-headed duck.
What is a ruddy duck?
The ruddy duck (Oxyura jamaicensis) is a small, compact duck species that is native to North America. Some key facts about the ruddy duck include:
- It gets its name from the male’s bright ruddy plumage during breeding season.
- It breeds primarily across central and western North America.
- It winters in coastal areas from British Columbia down to Mexico.
- It favors marshy wetlands with dense emergent vegetation.
- It feeds by diving and dabbling, eating aquatic invertebrates and vegetation.
- The female builds nests out of cattails and bulrushes near water.
- Clutch size is 5-15 eggs. The female alone incubates and cares for the young.
- Population estimates place the ruddy duck at about 650,000 individuals.
Key identification features include the male’s bright chestnut body, black crown and white cheek during breeding season. The female is duller brown. Both sexes have a slim, stiff tail that sticks upright when swimming and diving.
How did the ruddy duck become invasive in the UK?
The ruddy duck was introduced to the United Kingdom through escapes and releases from wildfowl collections beginning in the 1940s. By 2000, the UK population was estimated at around 6,000 breeding birds concentrated mainly in England and Wales.
Several factors allowed the ruddy duck to become so invasive in the UK:
- Lack of natural predators – With no predators to keep populations in check, ruddy ducks thrived in their new environment.
- Suitable habitat – The UK’s extensive wetlands, reservoirs and gravel pits provided ideal ruddy duck habitat.
- Mild climate – The UK’s relatively mild winters enabled better overwinter survival compared to the ruddy duck’s native range.
- Aggressive behavior – Ruddy ducks compete aggressively for resources, enabling them to dominate British duck populations.
- Rapid reproduction – Ruddy ducks mature early and have large broods, fueling rapid population growth.
Within several decades, the ruddy duck had become the most numerous duck species breeding in the UK after the mallard. Their invasive expansion across Europe had begun.
What threats did they pose in Europe?
The large and growing population of ruddy ducks in the UK posed a significant threat to native European ducks, especially the endangered white-headed duck.
Hybridization with white-headed duck
The main concern was hybridization between male ruddy ducks and female white-headed ducks. White-headed ducks have declined to only about 15,000 individuals worldwide. Cross-breeding with invasive ruddy ducks threatened to diminish the genetic purity of white-headed duck populations.
Competition for resources
Ruddy ducks also compete directly with native duck species like pochards, tufted ducks and scaup for food and nesting resources. Their aggressive behavior enabled them to dominate British wetlands, reducing resources available for native ducks.
Risk of disease introduction
Translocating birds also carried the risk of accidentally introducing new avian diseases to native European ducks that have no immunity. Diseases like avian influenza posed a concern.
Control and eradication efforts
Beginning in 1991, conservation authorities in the UK initiated programs to control and eradicate ruddy ducks. The main methods used included:
Egg oiling or pricking
Eggs in ruddy duck nests were coated in oil or pricked with needles to kill the embryos and prevent hatching. However, this was labor intensive and ineffective on a large scale.
Bird culling
Recreational and professional hunting of ruddy ducks was encouraged. Approximately 7,000 ruddy ducks were culled between 1991-2000 in the UK.
Live capture and euthanasia
The most effective method turned out to be live capture of males and females, followed by humane euthanasia of the adults. Trapping at key sites prevented birds from dispersing and nesting.
By 2010, the UK ruddy duck population had been reduced to just 155 individuals, mostly limited to northwest England. Complete nationwide eradication is still the goal.
Similar culling and control programs were enacted in France, Spain, Portugal and the Netherlands to remove ruddy duck populations starting to colonize from the UK. The success of ruddy duck eradication in Europe so far has been a model for tackling other invasive species problems.
Is the ruddy duck still invasive elsewhere?
While ruddy ducks have now been nearly eliminated from Europe, they continue to be considered an invasive species in some other parts of their introduced range.
United Kingdom
As mentioned, ruddy ducks are now very rare in the UK but still present in low numbers, requiring continued management.
Iceland
Around 2,000 ruddy ducks were introduced to Iceland from Canada and Alaska between 1930-1970 for hunting. They threaten native waterfowl through competition and hybridization. Culling programs are being attempted.
South Africa
A small introduced population of ruddy ducks exists in South Africa, centered around Cape Town. The African white-backed duck may be threatened by hybridization. Measures are now being implemented to prevent further colonization.
So while successful control in Europe has been achieved, the ruddy duck remains a concern as an invasive species in parts of its introduced range like Iceland and South Africa. Continued culling and population management is required where they risk hybridizing with endangered waterfowl.
Conclusion
In summary:
- Ruddy ducks were introduced to the UK from captive collections starting in the 1940s.
- They rapidly expanded to over 6,000 birds, threatening native ducks through hybridization, competition and disease transmission.
- Control measures like egg oiling, shooting and capture/euthanasia have now nearly extirpated them from Europe.
- However, small invasive populations persist in parts of Iceland, South Africa and the UK requiring continued management.
- So while ruddy ducks are native to North America, they have proven to be an invasive species requiring control where introduced outside their natural range.
Their story provides an important lesson on the harms invasive species can cause when translocated to new ecosystems. Care must be taken to prevent future unintended releases or escapes of the ruddy duck and other potentially invasive waterfowl around the globe.
References
- Banks, A.N., Wright, L.J., Maclean, I.M.D., Hann, C. & Rehfisch, M.M. 2008. Review of the Status of Introduced Non-Native Waterbird Species in the Area of the African-Eurasian Waterbird Agreement: 2007 Update. BTO Research Report No.489. BTO, Thetford, UK.
- Callaghan, D.A. 1997. Ruddy Duck Oxyura jamaicensis. In: The EBCC Atlas of European Breeding Birds: Their Distribution and Abundance (Eds. Hagemeijer, W.J.M. & Blair, M.J.). Poyser, London. pp. 176-177.
- Green, A.J. & Hughes, B. 1996. The status and distribution of the ruddy duck Oxyura jamaicensis in the Western Palearctic and an action plan for its eradication, 1996-2000. In: Proceedings of the Anatidae 2000 World Conference, Strasbourg, France, 5-9 December 1994. Gibier Faune Sauvage, Game Wildlife 13(Special Issue):129-134.
- Holmes, J.S. & Simons, J.R. 1996. The introduction and naturalisation of the ruddy duck Oxyura jamaicensis in the Western Palearctic. British Birds 89:481-486.
- Hughes, B., Criado, J., Delany, S., Gallo-Orsi, U., Green, A.J., Grussu, M., Perennou, C. & Torres, J.A. 1999. The status of the North American ruddy duck Oxyura jamaicensis in the Western Palearctic: towards an action plan for eradication. Council of Europe, Strasbourg, France.
- Muñoz-Fuentes, V. et al. 2007. Hybridization between white-headed ducks and introduced ruddy ducks in Spain. Molecular Ecology 16:629–638.