Conservation Priority Species Progress of the UK Ruddy Duck eradication programme Iain Henderson Alan Harris Ruddy Ducks Oxyura jamaicensis and Tufted Ducks Aythya fuligula ABSTRACT The non-native Ruddy Duck Oxyura jamaicensis became established in the UK in the 1960s following escapes and releases. During the 1970s and 1980s it spread throughout the UK and was seen with increasing frequency in mainland Europe. Hybridisation with the Endangered White-headed Duck O. leucocephala was first recorded in Spain in 1991, and this is now regarded as the greatest threat to the long-term survival of the latter species. A programme aiming to protect the White-headed Duck by eradicating Ruddy Ducks from the UK began in 2005. Over 6,200 Ruddy Ducks have been culled at over 110 sites across England, Scotland and Wales under this programme, and data suggest that by winter 2008/09 the UK population had been reduced by almost 90%. Introduction originates from four males and three females On a global scale, invasive non-native species imported to the Wildfowl & Wetlands Trust are second only to habitat loss as a cause of (WWT) at Slimbridge, Gloucestershire, in 1948. extinctions (Lowe et al. 2000). This can result A captive-breeding programme started in 1949 from competition, habitat degradation or but, following a series of escapes in the mid to hybridisation. The Ruddy Duck Oxyura late 1950s and the deliberate release of three jamaicensis is a native of the Americas, where it immature females in 1961 (Hudson 1976), a has a stable population of around 500,000 birds small feral population became established in (Wetlands International 2006), but is an intro- southwest England. Breeding in the wild duced species in Europe. The UK population appears to have first occurred in 1960, at Chew 680 © British Birds 102 • December 2009 • 680–690 Progress of the UK Ruddy Duck eradication programme Valley Lake, Avon (King 1976), and during the tion and the increase in records in mainland 1960s and early 1970s the breeding range spread Europe suggests that escapes from captivity are slowly to other counties – Staffordshire in 1961, not the main source of birds in Europe. In addi- Gloucestershire by 1963, Shropshire in 1965, tion, the appearance of winter flocks of 30–40 and Cheshire in 1972 (Hudson 1976). From the birds in France (winter 1995/96) and Spain mid 1970s, the size of the UK Ruddy Duck pop- (January 1997, following freezing conditions ulation began to grow much more rapidly, and across northern Europe) cannot be explained the range began to expand significantly. by escapes from captivity (Hughes 1996). By Breeding was first proved in Northern Ireland 1999, annual breeding attempts were believed to in 1973 (Allen & Mellon 2006) and by 1997 the occur in at least six countries in the Western UK breeding population had spread as far as Palearctic, in addition to the UK: Iceland, Orkney (Scottish Bird Report 1997). In January Ireland, the Netherlands, Belgium, France and 2000, the UK population was estimated at c. Morocco (Hughes 1999). However, in the last 6,000 birds (Kershaw & Hughes 2002). ten years the development of the populations in these countries has been patchy, and only the Ruddy Ducks in Europe Netherlands and France appear to have The period of growth and spread of the UK breeding populations of more than ten pairs. population was reflected on the Continent, The Netherlands had approximately 16–20 where the number of records increased at a breeding pairs in 2008 (Erik van Winden pers. mean annual rate of 21% between 1976 and comm.) while France had around 40–60 1996 (Hughes et al. 1999). DNA analysis has breeding pairs in 2007 (Alain Caizargues pers. been carried out comparing Ruddy Ducks from comm.). Ruddy Ducks in France are concen- North America with specimens from Europe, trated in the northwest of the country and including captive birds in the UK and wild birds numbers have continued to increase slowly, culled in Iceland, the UK, France and Spain. despite 120–140 birds being culled annually in The results confirm that the European Ruddy recent years. In the Netherlands, however, peak Duck population (including the birds shot in winter counts have fallen in recent years, from Iceland) is likely to derive solely from the 97 in winter 2005/06 to 60 in winter 2008/09. captive population in the UK (Muñoz-Fuentes This fall has occurred without any control of et al. 2006). Although captive birds are also the population in the Netherlands, and suggests present in some European countries, the close that there may be movement of birds between correlation between the rise in the UK popula- southeast England and the Netherlands, and www.nature-photography.co.uk Mike Lane Mike 441. Male White-headed Duck Oxyura leucocephala, southern Spain, April 2008. British Birds 102 • December 2009 • 680–690 681 Progress of the UK Ruddy Duck eradication programme that control of the population in the UK has now restricted to Spain, which is the only been responsible for the decline in numbers. region where the White-headed Duck has Numbers of Ruddy Ducks in other European expanded its breeding range and population countries remain very low but, given the experi- size in recent years (Hughes et al. 2006). The ence in the UK, it is important to avoid compla- Spanish population had fallen to as few as 22 cency. In Belgium, one pair attempted to breed birds, at just one location in Cordoba, by 1977 in 2006 but the birds disappeared before they (Torres 2003), but numbers had increased to a could be culled. Another pair attempted to breed recent peak of almost 4,500 in autumn 2000, in 2007 but the two birds were successfully shot following a particularly good breeding season, (Wouter Fayvets pers. comm.). In 2008, three and the post-breeding population now appears pairs were recorded in a Special Protection Area to have stabilised at between 2,100 and 2,600 at Antwerp Harbour, and seven young raised. individuals (Carlos Gutierrez pers. comm.). Because of the presence of other breeding water- Small numbers have been released into the wild birds (most notably a Eurasian Spoonbill in recent years. These are the surplus birds from Platalea leucorodia colony), the shooting of these a captive-breeding programme that uses stock birds was not possible. Up to five pairs were of Spanish origin (Torres 2003; Carlos present in this area in May 2009 (Wouter Fayvets Gutiérrez pers. comm.), and which was estab- pers. comm.) and two adult males, three adult lished in the early 1980s as insurance against the females and five pulli were shot in August 2009 potential loss of the small wild population. (Hans van Gossum, pers. comm.). Numbers in However, the increase in numbers was mainly the Republic of Ireland appear to have fallen in the result of a hunting ban which came into line with the decline in the UK population, effect in 1980, and habitat protection that has despite no organised control programme, and safeguarded the key breeding and wintering most records are now of single birds. Compre- sites for the species (Carlos Gutiérrez pers. hensive data from Morocco are difficult to comm.). In 2007, breeding occurred on 32 sites obtain but one possible Ruddy Duck x White- across 11 provinces in southern and eastern headed Duck hybrid was reported near Rabat, Spain (Carlos Gutiérrez pers. comm.). with two White-headed Ducks, in April 2009 In 1983, the first feral Ruddy Duck was (Ana Iñigo in litt.). In Germany, only one recorded in Spain, raising concerns about the breeding pair has been recorded since 2000 – in risk of hybridisation with the White-headed Lower Saxony in 2001, 2002 and 2003 (Gerhard Duck. Ruddy Ducks have been recorded annu- Adams pers. comm.). Although there have been ally in Spain since 1991, and the first Ruddy rare observations during the breeding season in Duck x White-headed Duck hybrids were northwest Germany in more recent years, no observed in the same year (Hughes et al. 1999). broods have been confirmed (Friederike Woog In the early 1990s, several hybrids were culled in in litt.). No birds have been recorded in Iceland Spain as the authorities developed an effective since a single male in April 2004 (Oli Nielson control and reporting programme (fig. 1). At pers. comm.). least 182 Ruddy Ducks have been recorded, in 19 provinces, since 1991 (Carlos Gutiérrez pers. White-headed Ducks and the threat posed by comm.) and introgressive hybridisation with the Ruddy Duck the Ruddy Duck is now the greatest long-term The White-headed Duck is listed as Endangered threat to the White-headed Duck’s survival on the IUCN Red List of Threatened Animals (Hughes et al. 2006). (Hughes et al. 2006; IUCN 2009). It belongs to Although many people focus on the small the same stifftail genus as the Ruddy Duck but numbers of Ruddy Ducks that currently arrive the two species have been geographically iso- in Spain, it is the threat posed by range expan- lated without any gene flow between them for sion of the Ruddy Duck that is the greater risk. between two and five million years (McCracken The Spanish authorities currently have a well- et al. 2000). The White-headed Duck was for- organised control programme, which can deal merly found throughout southern Europe, parts with the few Ruddy Ducks that appear annually, of North Africa and much of central Asia, but and the numbers arriving in Spain have in fact its breeding areas are now highly fragmented, fallen since the start of the UK eradication pro- principally due to habitat loss and over- gramme.