Vagrants, migrants and colonists
Like Painted lady butterflies and other insects, some species of dragonfly show strong tendencies to undergo long distance ‘migrations’ or large scale dispersals at irregular intervals when conditions are favourable and numbers high. By this means new areas may be colonised, sometimes only temporarily if conditions where they arrive are marginal for their survival.
Movements into the British Isles from Europe often include widespread species such as the Four-spotted chaser and the Common darter, but more excitingly for dragonfly enthusiasts, they can also include southerly species which have no permanent base here. The weaker damselflies are less often involved, but several species have been extending their permanent ranges quite rapidly in recent years, resulting in ‘new’ species entering the UK.
Being closest to the continent, the south and east of England are the most exposed to these influences and only a few stragglers from larger influxes seem ever to have reached Scotland. Red-veined and Yellow-winged darters Sympetrum fonscolombii and S. flaveolum for example have both been noted in Scotland on only a couple of occasions in the past hundred years. This is also true of the Vagrant emperor Hemianax ephippiger– a more solitary wanderer from warmer climates, which has the distinction of being the only dragonfly to be recorded in Iceland.
Though a common resident in southern Britain, the Brown hawker Aeshna grandis is as rare in Scotland as these continental species. An occurrence in the Hebrides in 2004 could perhaps have derived from Ireland, where it also breeds.
Several species have been extending their UK breeding ranges for many years. In the vanguard of these, the Common darter (as distinct from its resident ‘Highland’ form) has spread widely in Scotland after being scarce until the 1970s.
Since 2000, four species have reached Scotland for the first time. The Emperor dragonfly Anax imperator, Broad-bodied chaser Libellula depressa and Ruddy darter Sympetrum sanguineum were all seen in 2003 and Migrant hawker Aeshna mixta the following year. All these species are essentially lowland insects that will tolerate a wide range of habitats, and have the ability to act as ‘pioneers’ at relatively newly created sites. They will often turn up and breed for a few years and then re-appear elsewhere. They should be looked for especially near coasts, and most of all in the south and south-east of the country.