Letters
Ruddy Ducks
controlled in a limited way (e.g. Rook
Corvus frugilegus and Canada Goose
Branta canadensis). Would that, a hundred
years ago, some returning immigrant or sea
captain had brought back a few Huias Heteralocha acutirostris to release as an exotic
population breeding in the UK.
In Europe and beyond, there are instances
where island introductions have conserved
endemic birds that no longer exist in their
‘pure’ form on the mainland. Often, these are
game birds, but occasionally other sorts too.
They often thrive by filling a vacant biological or ecological niche – man-made or
natural.
Dr Bibby wrote that he was shocked by
‘sentimental’ arguments against the killing of
Ruddy Ducks Oxyura jamaicensis. I feel,
however, that he and the RSPB, an organisation founded and financed largely on sentiment, have rather lost the plot. As far as
sentiment goes, the lack of philosophical
debate on the Ruddy Duck question perhaps
shows the ‘conservation’ heart to rule the
head in attempting to ‘protect from extinction’ the White-headed Duck Oxyura leucocephala in a non-island situation.
Waterfowl of many species and in all
countries frequently hybridise under natural
circumstances, and no amount of mathematical modelling will prevent its happening. In
North America, it is estimated that around
B. Zonfrillo
Living in an ideal world, I could agree with
much of what Dr Colin Bibby said in his
article ‘More than enough exotics’ (Brit.
Birds 92: 2-3).The world is, however, far from
ideal, and I feel that he fell into the common
trap of tarring everything - particularly alien
birds and mammals – with the same brush.
As one who has spent the past decade at the
sharp end of island conservation, eradicating
rats Rattus from seabird colonies both at
home and abroad, I am perhaps suitably qualified to comment constructively on a few of
the many points that he raised. That all alien
species, harmful and harmless, should simply
be summarily dismissed as intolerable
requires a more prescient and balanced
opinion.
In these days of rapidly declining
numbers of Yellowhammers Emberiza citrinella caliginosa and Song Thrushes
Turdus philomelos clarkei in the UK, I find it
somehow reassuring that on the other side
of the Globe, in New Zealand, a hundred
years or more after introduction, there still
exists thriving populations of both these
endemic UK subspecies. For whatever the
reason, their introduction to a distant island
has meant that not all the eggs are in one
basket. According to the NZ Department of
Conservation, there are no plans for the mass
extermination of any these introduced alien
birds. Only species damaging agriculture are
218. Ruddy Ducks Oxyura jamaicensis, near Glasgow, Scotland (exact location withheld).
394
© British Birds 93: 394-398, August 2000
B. Zonfrillo
Letters
lay 8-12 eggs, this could be interpreted as the progeny of a single
hybrid pairing. If that is not the case,
then maybe no more than a few
hybrid pairings are involved. For the
Department of the Environment,
Transport and the Regions, supported
and endorsed by many UK conservation bodies, to commit £800,000 of
‘conservation’ money for regional
trials alone to such a biological nonthreat is a folly bettered only by the
hundreds of millions of pounds of
taxpayers’ money spent on that functionless appendage in London, the
219. Canada Goose Branta canadensis × Greylag Goose
Millennium Dome. Perhaps some cash
Anser anser feral hybrid (one of about 15 individuals),
could be better spent educating the
Glasgow, Scotland.
Spaniards as to the improbability of
gene swamping of their study species.
10% of all breeding bird species, waterfowl
How many UK seabird islands could be
included, have recorded hybrids. Mallards
cleared of harmful alien mammal species
Anas platyrhynchos have hybridised with 23
with a budget of £800,000? Most, I would say.
other duck species worldwide. Instances of
As is well known, the problems of the
gene ‘swamping’ are globally few, and there is
White-headed Duck decline are related to
none at all among European ducks. I can find
generations of over-hunting both in Spain
no case of any bird species being completely
and farther east in its range. Use of monofila‘bred out’ anywhere else in the World. Thus,
ment fishing nets in eastern countries also
there is as much chance of the Ruddy Duck
account for killing many diving ducks,
genetically swamping the White-headed
including White-headed.The Ruddy Duck has
Duck as there is of the Common Pochard
also been hunted to perilously low numbers
Aythya ferina genetically swamping the
over much of its Caribbean islands breeding
Tufted Duck Aythya fuligula or the Canada
range, a fact often overlooked. Maybe the
Goose the Greylag Goose Anser anser.
thriving UK population can be used to help
Doubtless their offspring are also fertile.The
increase numbers there?
Tufted x Pochard and Canada x Greylag
Arguments used for the killing of Ruddy
hybrids are more common in Europe than
Ducks in the UK are scientifically ‘wobbly’,
are Ruddy x White-headed Duck hybrids.
and the method of execution verges on the
While a few Oxyura hybrids in Spain are an
banal. How much illegal ‘wilful disturbance’
irritation, they are probably, like other
will shooting create at sites where Ruddy
hybrids, irrelevant to the evolutionary mainDucks occur alongside Schedule 1 species?
tenance of the general populations of one or
While the DETR, the RSPB and others are
both species. If the Ruddy Duck was inclined
happy to commit their/our money and
to swamp its congeners genetically, the
support to the Ruddy Duck fiasco, there are
Masked Duck Oxyura dominica would
many local conservation projects deserving
surely have vanished from the West Indies
of priority funding.
long ago? Indeed, the two ver y similar
Many of our island National Nature
Oxyura ducks of Argentina O. vittata and
Reser ves, RSPB Reser ves, and the like,
Peru O. j. ferruginea are regarded as distinct
harbour populations of harmful aliens, such
species largely because they do not interas rats, Minks Mustela vison and Rabbits
breed where their ranges overlap.
Oryctolagus cuniculus. The indifference
Looking at the published facts concerning
shown by the conservation organisations
the situation in Spain, it appears that, after
suggests that these harmful aliens are seemfour years of ‘intensive control measures’ a
ingly tolerated and, by default, ‘protected’.
total of 39 Oxyura hybrids was killed. Since,
Genuine conservation appears to have a low
like many ducks, those in the genus Oxyura
British Birds 93: 394-398, August 2000
395
Letters
priority among establishments with the
resources actually to carry it out. The bright
idea that it would be feasible to find and
then shoot all the Ruddy Ducks in Europe
defies belief. Never one for sentiment,
Audubon wrote of the Ruddy Duck: ‘I have
found this species hard to kill, and when
wounded very tenacious of life, swimming
and diving at times to the last gasp.’
The elevation of a rather small localised
conservation problem in Spain to an international conservation crisis requiring millions
of pounds to remedy in the UK alone speaks
volumes for those who have built a career
around biological scaremongering. I wish
that I had their powers of persuasion.
Bernard Zonfrillo
28 Brodie Road, Glasgow G21 3SB
Are Ruddy Ducks and White-headed Ducks the same species?
Stifftail ducks including the genera Nomonyx
and Oxyura are well known for their large,
well-developed feet and swimming muscles
set far towards the rear of the body, proficient diving abilities, and display-oriented
sexual behaviour (Raikow 1970; Livezey
1995; Johnsgard & Carbonell 1996). Six or
seven species of stifftail ducks are currently
recognised (Livezey 1995, 1997; McCracken
et al. 1999). These include the Masked Duck
N. dominicus of tropical South America,
Central America and the Caribbean, the
Ruddy Duck O. jamaicensis, which inhabits
both North America (O. j. jamaicensis) and
South America (two races: Andean Ruddy
Duck O. j. ferruginea in the Southern Andes;
Colombian Ruddy Duck O. j. andina in the
Northern Andes), and the Argentine Lake
Duck O. vittata, which also inhabits South
America. Each of the three remaining species
is endemic to each of the Old World continents, respectively: the Blue-billed Duck O.
australis in Australia, the Maccoa Duck O.
maccoa in Africa, and the White-headed
Duck O. leucocephala in Europe, Asia and
North Africa.The latter, now largely restricted
to small populations in Spain and central Asia
(e.g. Green et al. 1996), is potentially threatened with extinction through hybridisation
with introduced Ruddy Ducks from North
America (Hughes 1996a; Perennou 1997).
Viability and fertility of Ruddy Duck × Whiteheaded Duck hybrids has, however, raised
questions about whether the White-headed
Duck is a distinct species and, therefore,
whether control measures for feral Ruddy
Ducks (Green & Hughes 1996; Hughes
1996b) are appropriate.
Our analysis of stifftail evolutionary relationships, based on the sequences of the
mitochondrial genes for cytochrome b
(McCracken et al. 1999) and 12S rDNA
(Sorenson & Johnson, unpubl. data), is presented in fig. 1 † . This indicates that the
Masked Duck is the sister species of extant
Oxyura species. Within Oxyura, the New
World species (Argentine Lake Duck and
Ruddy Duck) diverged first, suggesting an
early expansion of ancestral stifftails out of
tropical areas and into temperate regions of
North and South America. Some time later,
stifftails colonised the Old World continents
of Australia (Blue-billed Duck), Africa
(Maccoa Duck), and Eurasia (White-headed
Duck). Our data indicate no close relationship between the Ruddy Duck and the
White-headed Duck, as would be the case if
these two species were sister groups or were
part of a recently evolved cluster of closely
related species, within which the evolutionary patterns would be unclear. On the
contrary, the closest relatives of the Whiteheaded Duck appear to be the Maccoa Duck
and the Australian Blue-billed Duck.
This point can be illustrated further by an
examination of genetic distances. For
cytochrome b, the genetic distance between
nominate Ruddy Duck and the White-headed
Duck is 5.65%.This value stands in stark contrast to a genetic distance of 0.20%, between
†
Cytochrome b and 12S rDNA genes were amplified from genomic DNA extracts using the polymerase
chain reaction (PCR) (e.g. Gyllensten 1989) and generalised bird primers. Purified light and heavy strand
PCR products subsequently were cycle-sequenced using BigDye Terminator Cycle Sequencing Kits,
followed by electrophoresis on ABI 377 automated DNA-sequencers (Perkin Elmer Applied Biosystems,
Norwalk, Connecticut). Sequences from opposite strands were reconciled using Sequence Navigator 1.0.1
(Perkin Elmer Applied Biosystems, Norwalk, Connecticut), verified for accuracy, and aligned by eye.
396
British Birds 93: 394-398, August 2000
Letters
the nominate race of the Ruddy Duck and
the southernmost of the two South American
races (O. j. ferruginea).The 5.65% divergence
between Ruddy Ducks and White-headed
Ducks also is substantially larger than the
genetic divergence among clearly distinct
dabbling duck species (genus Anas). For
example, the maximum divergence among
four species of pintails on three continents,
among 12 recognised ‘mallard’ species distributed worldwide, and among five species
of wigeons and gadwalls is 3.7%, 3.2%, and
5.4%, respectively (Johnson & Sorenson
1999). Similar trends are evident for 12S
rDNA. Although the distances are much
smaller due to the slower rate of evolution of
the 12S gene, the White-headed Duck is
closer to the African Maccoa Duck (1.85%)
and Australian Blue-billed Duck (1.36%) than
it is to the Ruddy Duck (1.95%). The 12S
rDNA genetic distance between the Ruddy
Duck and the White-headed Duck (1.95%) is
actually greater than that between some different waterfowl genera. For example,
steamer ducks Tachyeres and crested ducks
Lophonetta, representing two morphologically divergent waterfowl genera, differ by
1.90%; the Baikal Teal Anas formosa and the
Brazilian Teal Amazonetta brasiliensis, the
former from the Far East and the latter from
South America, also differ by 1.90%.
In summary, genetic divergence among
many morphologically distinct and geographically isolated waterfowl species is much
smaller than that observed between Ruddy
Ducks and White-headed Ducks. Genetic distance comparisons and phylogenetic
analyses clearly indicate that: (1) Ruddy
Ducks and White-headed Ducks have been
geographically isolated for several million
years, (2) there has been no gene f low
between the two lineages since their ancestors diverged (McCracken & Sorenson,
unpubl. data), and (3) the other two Old
World Oxyura are more closely related to
the White-headed Duck than any of the three
is to the Ruddy Duck. Recent hybridisation
between White-headed Ducks and introduced Ruddy Ducks should in no way be
taken as evidence that they belong to the
same species. Genetic compatibility among
species and viability of hybrids is well
known among waterfowl and other groups
of birds, and often extends to crosses
British Birds 93: 394-398, August 2000
Fig. 1. Maximum-likelihood tree based on a
phylogenetic analysis of 2,184 nucleotide
positions in the mitochondrial genes for
cytochrome b (McCracken et al. 1999) and 12S
rDNA (Sorenson & Johnson, unpubl. data). Loglikelihood (lnL) = –5666.09 (ti:tv = 6.24, p-inv =
0.54, a = 0.59). Numbers on each branch
indicate the number of nucleotides substitutions
inferred to have occurred using a maximumlikelihood model corrected for multiple hits by
the method of Hasegawa et al. (1985). Tree is
rooted on Black-headed Duck Heteronetta
atricapilla and Freckled Duck Stictonetta
naevosa.
between different genera (e.g. Sibley 1938;
Johnsgard 1960; Scherer & Hilsberg 1982).
To argue that Ruddy Ducks and Whiteheaded Ducks are one species because they
hybridise in a human-mediated contact zone
flies in the face of species concepts and
current views of systematic biologists about
the nature of species (e.g. Mayr 1963). In
sum, the notion that the Ruddy Duck and the
White-headed Duck are the same species has
no scientific merit. Every effort should be
made to implement control measures for
feral Ruddy Ducks and ensure the continued
reproductive success of the White-headed
Duck.
References
Green, A. J., Fox,A. D., Hilton, G., Hughes, B.,Yarar, M., &
Salathe,T. 1996.Threats to Burdur Lake ecosystem,
Turkey and its waterbirds, particularly the whiteheaded duck Oxyura leucocephala. Biol.Conserv.
397
Letters
76: 241–252.
Green, A. J., & Hughes, B. 1996. Action plan for the
White-headed Duck Oxyura leucocephala. Pages
119–146 in Heredia, B., Rose, L., & Painter, M. (eds).
Globally Threatened Birds in Europe. Council of
Europe Publishing, Strasbourg.
Gyllensten, U. B. 1989. PCR and DNA sequencing.
BioTechniques 7: 700–708.
Hasegawa, M., Kishino, H., & Yano, T. 1985. Dating of
the human-ape splitting by a molecular clock of
mitochondrial DNA. J. Mol. Evol. 22: 160–174.
Hughes, B. 1996a. The Ruddy Duck Oxyura
jamaicensis in the Western Palearctic under threat
to the White-headed Duck Oxyura leucocephala. In
Holmes, J. S., & Simons, J. R. (eds), The Introduction
and Naturalisation of Birds, pp. 79-86. London.
— 1996b.The feasibility of control measures for North
American Ruddy Ducks Oxyura jamaicensis in the
United Kingdom. Report to the Department of the
Environment.
Johnsgard, P.A. 1960. Hybridization in the Anatidae and
its taxonomic implications. Condor 62: 25–33.
— & Carbonell, M. 1996. Ruddy Ducks and Other
Stifftails: their behavior and biology. Norman,
Oklahoma.
Johnson, K. P., & Sorenson, M. D. 1999. Phylogeny and
biogeography of dabbling ducks (genus: Anas): a
comparison of molecular and morphological
evidence. Auk 116: 792–805.
Livezey, B. C. 1995. Phylogeny and comparative
ecology of stifftailed ducks (Anatidae: Oxyurini).
Wilson Bull. 107: 214–234.
— 1997. A phylogenetic classification of waterfowl
(Aves: Anseriformes), including selected fossil
species. Ann. Carnegie Mus. 66: 457–496.
Mayr, E. 1963. Animal Species and Evolution.
Cambridge, Massachusetts.
McCracken, K. G., Harshman, J., McClellan, D. A., &
Afton, A. D. 1999. Data set incongruence and
correlated character evolution: an example of
functional convergence in the hind-limbs of stifftail
diving ducks. Syst. Biol. 48: 683–714.
Perennou, C. 1997. The problem of the introduction
of an aquatic bird, the Ruddy Duck (Oxyura
jamaicensis). B. Fr. Peche. Piscic. 344–45: 143–151.
Raikow, R. J. 1970. Evolution of diving adaptations in
the stiff-tailed ducks. Univ. Calif. Publ. Zool. 94:
1–52.
Scherer, S., & Hilsberg, T. 1982. Hybridisierung und
Verwandtschaftsgrade innerhalb der Anatidae—
eine systematische und evolutionstheoretische
Betrachtung. J. Orn. 123: 357–380.
Sibley, C. L. 1938. Hybrids of and with North American
Anatidae. Proc. Int. Orn. Congr. 9: 327–335.
Kevin G. McCracken
University of Alaska Museum, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
J. Harshman
4869 Pepperwood Way, San José, CA 95124, USA
Michael D. Sorenson
Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA
Kevin P. Johnson
Illinois Natural History Survey, 607 East Peabody Drive, Champaign, IL 61820, USA
Origin of the first Lesser Frigatebird in the Western Palearctic
In their paper documenting the record of a
Lesser Frigatebird Fregata ariel in Israel, Dr
Roger Riddington and Jane Reid (2000)
stated that the species’ breeding range is
centred on Australia and the central Pacific
save for a small population in the South
Atlantic. The distance from the nearest
colony to Israel would, thus, be well over
10,000 km.
May I, however, bring to your attention
the fact that large numbers breed on the
Aldabra Atoll, in the Indian Ocean north of
Madagascar, at roughly 08°50’S 46°45’E.
A.W. Diamond (in Penny 1977) estimated the
total number of frigatebirds breeding on
Aldabra at about 30,000 birds, the majority
being Lesser Frigatebirds (Beamish 1970).
According to Penny (1977), non-breeders
and failed breeders leave Aldabra between
November and July, when they are commonly seen north of Aldabra (in central Seychelles). A more-or-less direct flight from
Aldabra to Eilat could be less than 5,000 km,
a similar distance to that which a Magnificent Frigatebird Fregata magnificens would
have to cover from the Caribbean to northwest Europe. Thus, Aldabra is a far more
likely origin for the Eilat bird than is Australia, let alone the Pacific.
References
Beamish,T. 1970. Aldabra Alone. London.
Penny, M. 1977. The Birds of the Seychelles and the
Outlying Islands. Glasgow.
Riddington, R., & Reid, J. 2000. Lesser Frigatebird in
Israel: new to the Western Palearctic. Brit. Birds 93:
22-27.
Norman D. van Swelm
Voorne Bird Observatory, Schepenenweg 26, 3233 CL Oostvoorne, Netherlands
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