Invasive Alien Species in Northern Ireland

Oxyura jamaicensis, Ruddy Duck

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Oxyura jamaicensis
© Tom Ennis
Oxyura jamaicensis
© Tom Ennis
Oxyura jamaicensis
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Oxyura jamaicensis (Gmelin)
 
Introduction
The ruddy duck is an introduced species from North America which colonised Ireland some years after escaping from a waterfowl collection in England. In the last fifteen years the impact of this species on its closely related cousin, the white-headed duck, has been the cause of much concern. Hybridisation could threaten the existence of the much rarer white-headed duck. The white-headed duck does not occur in northern Europe, the closest population being in southern Spain. Ruddy ducks have migrated as far as these breeding areas, prompting proposals for a widespread programme of ruddy duck eradication.
 
Description
The ruddy duck is a member of the group of wildfowl known as the “stiff-tails”, so named because of their long, stiff tail feathers. They are a small, compact duck (35-43cm long including 6-8cm tail) with a characteristic vertically held tail and proportionately large head and bill. A summer-plumaged male is unmistakable with its deep chestnut body plumage, white cheeks, black cap and bright blue bill. The females and immatures are more cryptically marked, being a duller brown and having buff cheeks and a dark bill.
 
Country of origin
The ruddy duck’s native range is in the Americas. The native North American population numbers some 500,000 birds with a further 10,000 in Central America and north Colombia (O.j. andina). The birds in South America are now considered a separate species (Oxyura (jamaicensis) ferruginea).
 
Current distribution
In the UK it escaped from captivity in the 1940s and first bred in the wild in 1960, soon forming a self-sustaining feral population. By 1998 the UK population had increased to about 4,000 birds. Birds originating from the UK have now occurred in a range of countries throughout the Western Palaearctic (Europe, central Asia and North Africa).
 
Location in Ireland
The first ruddy duck in Ireland was discovered at Oxford Island NNR, County Armagh in March 1973, with breeding taking place the same year. In the 1980s the species had expanded to other sites and in 1986 the population was around 27-30 birds concentrating in winter, at their now favoured site, Portmore Lough, County Antrim. By the early 1990s the population had grown significantly, reaching a maximum of 206 birds in January 1996. This peak has never been repeated since and was probably part of a weather-related movement from Great Britain. However, some birds remained, boosting the small, apparently resident population.
The current breeding population in Northern Ireland is estimated at 25 to 30 pairs with a wintering population of around 70 to 75 birds. These figures were obtained through a year-long study of the species in Northern Ireland, undertaken by Environment and Heritage Service.
The expansion into the Republic of Ireland is less well documented but individual birds were being recorded in the late eighties in a few counties. Breeding has been proved in Counties Dublin, Wexford, Limerick and Tipperary but this is certainly not the total picture. Numbers may be underestimated due to the secretive nature of the species and it is possible that the total Republic of Ireland population may be larger than is currently thought.
 
Life cycle
The biology and ecology of the ruddy duck have been well studied in both North America and Britain. In winter, ruddy ducks are highly gregarious, forming large flocks on a variety of waterbodies, often concentrated in a few key sites (Portmore Lough in the case of Northern Ireland). The gregarious nature during the winter is in stark contrast to the ruddy duck's breeding behaviour when the population becomes highly dispersed. Ruddy ducks prefer to breed on small reed-fringed pools where they nest over water in emergent vegetation. Most sites hold just one or two pairs.
Ruddy ducks usually appear on breeding sites from late February onwards. Pairs form in early April, and laying begins in May. Breeding then continues until September and newly-hatched broods have been seen as late as November. They are not known to have second broods in the UK. Shortly after pairing, the birds become secretive as they try to avoid the attentions of unpaired males. In contrast, unpaired males are very obvious as they rove around potential breeding sites in search of mates. Incubating females are usually well concealed in vegetation and attendant males often loaf a few metres away. Females with young broods are secretive and remain hidden in waterside vegetation. By three weeks the young are totally independent and have fledged by eight weeks. Ruddy ducklings are very well developed when they hatch and can dive from only two days old. Where a number of pairs occur, broods often merge into unattended crèches.
 
Wildlife and habitat impacts
The ruddy duck’s introduction into the UK, and its expansion to other parts of Europe and North Africa (41 countries to date), has potentially disastrous implications for its close relative, the white-headed duck (Oxyura leucocephala). The majority of these wanderers are males which outcompete male white-headed ducks for females producing fertile hybrids. Where pairs of ruddy ducks occur with white-headed ducks they are more aggressive and can outcompete them for nesting space and food. At present, hybridisation has been restricted to countries in the western Mediterranean. The threat to the white-headed duck should not be underestimated. Recent DNA work shows that the two are genetically very different species, though closely related, and that interbreeding will result in the eventual extinction of the white-headed duck. For this reason an Action Plan has been drawn up and agreed by all countries where the species occur. The key objective is to exterminate all ruddy ducks in the Western Palaearctic, including both feral and captive birds. Ruddy ducks have no impact on habitats.
 
Human impacts
While most conservationists support the control measures, some animal welfare groups have expressed concern about the plans to eradicate the ruddy duck and the methods proposed. Since the mid-1990s trial control has taken place in parts of Great Britain to test the feasibility of a complete cull. A web site link to the final report on this trial is included as a link in Information.
 
Key vectors
The continued presence of ruddy duck’s in private wildfowl collections would need to be addressed if the long-term objectives in the white-headed duck Action Plan are to be met. Ruddy ducks are capable of long-distance migrations.
 
What you can do as an individual
Birdwatchers’ should report all sightings of ruddy ducks in Northern Ireland to the Northern Ireland Birdwatchers’ Association, Flightline. Tel: 028 9146 7408. All information received is logged into a database held by the Ulster Museum, which can provide up-to-date, as well as historical information on the species. Any eventual control will be undertaken by professional individuals trained in the various control measures to be employed.
 
Advice to specific groups relevant to this species
Birdwatching groups and field clubs on field outings should be encouraged to follow the same procedure as above.
 
Management measures
Management measures will rely on up-to-date information so as to allow targeted actions. Such actions are likely to include shooting of individuals and egg pricking to reduce productivity.
 
Management groups
Department of Environment, Food and Rural Affairs (DEFRA) — Helpline, Tel: 08459 335577 — are responsible for the UK’s implementation of the white-headed duck Action Plan and hence any actions relating to ruddy ducks.
Environment and Heritage Service (NI). Tel: 028 9025 1477 — are responsible for monitoring the ruddy duck in Northern Ireland.
Wildfowl and Wetlands Trust (Threatened Species Department) — Dr Baz Hughes, WWT, Slimbridge, Gloucester, GL2 7BT. Tel: 01453 891916.
RSPB, The Lodge, Sandy, Beds, SG19 2DL. Tel: 01767 680551.
 
Further information
Links
This web site provides the scientific background to the problem with ruddy ducks and white-headed ducks.
http://www.wwt.org.uk/threatsp/hybrid/index.htm
Papers explaining the need for the eradication of ruddy ducks throughout the Western Palaearctic.
http://www.wwt.org.uk/threatsp/twsg/bulletins/12/F3.htm
A report on the results of the trial ruddy duck cull in the UK.
http://www.defra.gov.uk/wildlife-countryside/scientific/ruddy/ruddy1/Fullreport.pdf
A brief summary of the ruddy duck control trials up to 2003.
http://www.defra.gov.uk/wildlife-countryside/resprog/findings/ruddy/trial.htm
Birdguides provide a simple identification page with images.
http://www.birdguides.com/html/vidlib/species/Oxyura_jamaicensis.htm
 
Literature
Perry, K.W., Wells, J.H. and Smiddy, P. (1998). Recent increases in range and abundance of Ruddy Ducks in Ireland, 1995-98. Irish Birds 6: 2.
Wells, J.H. and Smiddy, P. (1995). The Status of the Ruddy Duck in Ireland. Irish Birds 5: 3.
 
See the Invasive Species Ireland web site for further information -
http://www.invasivespeciesireland.com/mostunwanted/
 
Text written by:
Allen & Mellon Environmental Ltd.