1st European Congress on Odonatology Programme and abstracts

Migrant Dragonflies in the UK: Distributions are flexible,
especially in times of climate change
Adrian J. Parr 1
1 10 Orchard Way, Barrow, Bury St Edmunds IP29 5BX, Great Britain.
Dragonfly migration is perhaps most obvious in the large-scale wanderings of Hemianax ephippiger
and Pantala flavescens in the tropical/sub-tropical Old World, and in the north-south movements of a
number of species, such as P. flavescens, P. hymenaea and Anax junius, in North America. Regular
long distance migration in Europe is apparently less pronounced, but Sympetrum fonscolombii is an
important example and the phenomenon is likely under-appreciated. Arrivals of rare species (such as
Anax parthenope and Aeshna affinis in northern Europe) will thus attract attention, but any arrivals of
more common species will be less obvious. In addition to this type of movement, other species show
related phenomena, with e.g. S. flaveolum and Libellula quadrimaculata intermittently producing
large-scale ‘irruptions’. Other species, such as e.g. Lestes barbarus, Ischnura pumilio and Erythromma
viridulum can also be highly dispersive under suitable conditions.
In response to climate change, arrivals of migrant dragonflies in Britain have altered dramatically over
the last 2 decades, and at present new species are being recorded about once every other year.
Presumably the breeding ranges of the species involved are expanding closer towards Britain, and/or
weather conditions facilitating migration are becoming more frequent. Following the increased arrival
of migrants, a number of species have started to breed. E. viridulum in particular has established a
substantial population in the UK, in line with events elsewhere in NW Europe. The ability of E.
viridulum to travel in large groups (influxes of 200 individuals at a single site have been observed) has
no doubt facilitated colonisation. The chances of all migrant species permanently colonising Britain,
even with favourable climatic conditions, is however less clear. It is possible that while ‘facultative’
migrants might readily colonise, ‘obligate’ migrants may have a nomadic lifestyle that prevents
permanent self-supporting colonies being produced. Although S. fonscolombii and probably A.
parthenope now breed in the UK in most years, much still remains to be discovered about their
precise breeding status. In particular, locally-bred second generation individuals of S. fonscolombii
disperse rapidly and may not contribute to colony stability (further study at a pan-<strong>European</strong> level is
required to determine exactly where they go). By analogy with the American A. junius, it is however
possible that some migrant species may in time develop a more sedentary sub-population that does
become resident.
The phenomenon of dragonfly migration is an interesting and complex one. In contrast to the
situation with e.g. bird migration, the underlying biological principals are only now being unraveled.
The impact of migration on both short- and long-term Odonate distributions is also now becoming
increasingly appreciated, though here too further research is still needed. The extent to which species
will respond differently to ongoing climate change is, for example, a key area for further study. The
present increased co-operation in <strong>European</strong> dragonfly research should go a long way towards helping
answer many of the remaining unresolved issues.
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