Aliens Newsletter - ISSG

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The arrival of Ruddy Ducks in Europe
As the UK population grew and its breeding range
spread, increasing numbers of Ruddy Ducks began
to appear in Europe, most notably in the countries
adjoining the UK such as France, Belgium and the
Netherlands. DNA analysis has confirmed that the
European Ruddy Duck population is likely to derive
solely from the captive population in the UK
(Muñoz-Fuentes et al. 2006). Captive birds are also
present in some European countries, but the close
correlation between the rise in the UK population
and the increase in records in mainland Europe suggests
that escapes from captivity are not the main
source of birds in Europe. In addition, the appearance
of winter flocks of 30–40 birds in France (winter
1995/96) and Spain (January 1997, following
freezing conditions across northern Europe) cannot
be explained by escapes from captivity (Hughes
1996). By 1999 the breeding range of Ruddy Ducks
in the UK included most suitable habitat in England
and Wales as well as several areas of Scotland and
parts of Ireland. By January 2000, the UK population
was estimated at c. 6,000 birds (Kershaw &
Hughes 2002). Annual breeding attempts were also
believed to occur in at least six countries in the
Western Palearctic, in addition to the UK: France,
the Netherlands, Belgium, Ireland, Iceland and Morocco
(Hughes 1999).
The background to the eradication programme
in the UK
By the early 1990s, when the UK held around 95%
of all the Ruddy Ducks in Europe, it had become
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Figure 4. Numbers of Ruddy Ducks recorded in Spain, 1984-2009
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clear that to do nothing would eventually allow Ruddy
Ducks to spread through the continent. The Spanish
authorities would then find it increasingly difficult
to prevent the establishment of Ruddy Ducks
with the attendant risk of increasing levels of hybridisation
between Ruddy Ducks and White-headed
Ducks. Given that White-headed Ducks in Spain
are now protected from hunting and habitat loss, it
is generally recognised that introgressive hybridisation
with the Ruddy Duck is now the greatest longterm
threat to the White-headed Duck (e.g. Hughes
et al. 2006).
The case of the Ruddy Duck is unique in that action
has been taken in one country to protect a
species in another. Ruddy Ducks were regarded by
many as an attractive and harmless addition to the
British avifauna, and to a lesser degree this remains
the case. Many in the UK took the view that if the
Ruddy Duck was a problem it should be dealt with
in Spain. It was also highly uncertain whether control
of Ruddy Ducks in the UK was feasible (particularly
to the point of eradication), how much eradication
might cost, and whether it would be acceptable
to the general public. For these reasons the UK
Government commissioned small-scale research into
control in the early 1990s. This involved the
culling of fewer than 100 birds per year and had no
significant effect on the population, but the results
indicated that breeding-season shooting was the
most effective method of control, followed by winter
shooting. Although nest trapping had a high intrinsic
efficiency, the rate of control in terms of staff
effort was very low and the method would therefore
be an ineffective means of attempting eradication.
The report concluded that eradication was feasible
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