Dragon Hunt 2012

Nope, this is not about Harry Potter or video-gaming, so if that's what brought you here, sorry - but do feel free to stay and read on... instead, it's about Hampshire Conservation Volunteers' annual pilgrimage to see the dragonflies in one of the most Odonata-friendly parts of the New Forest.

This year's event which took place last Sunday was of particular interest as it follows an exceptionally wet early to mid-summer in Britain which has led to dire predictions about the fate of many invertebrate species, a topic I've looked at briefly here. Of course, the Odonata (damselflies, demoiselles and dragonflies - all of which are illustrated below) are aquatic as juveniles, and require water to breed as adults, so it is less clear what effect wet conditions might have than, for example, on butterflies. However, with heavy rains come lower-than-average temperatures, so some of the same impacts might be seen in the adults, such as difficulties finding food and mates.

For those not familiar with Odonata, the damselflies and demoiselles (suborder Zygoptera) are slender-bodied and hold their wings closed lengthways at rest, while the dragonflies (infraorder Anisoptera) are more robust 'typical' Odonata and hold their wings open at rest. There is another infraorder of dragonflies, the Epiophlebioptera, but most of these are extinct with just three Asian species currently known (the third was discovered recently in China by Li et al., 2012) - I won't worry about these here, so back to the Dragon Hunt...

Our first stop was Hatchet Pond, a well-known Odonata-watching spot where it is possible to track down some botanical rarities too (more on that another time) and which provided us with good views of familiar species such as Common blue damselfly (with various female colour forms, and both pale-immature and blue-mature males, plus egg-laying behaviour seen) and an Emperor dragonfly patrolling a section of the large pond (it's the largest in the New Forest). However, although we visited a couple of the small nearby ponds as well, the best views of the day - and the most interesting records - were around the nearby stream at Crockford, where one of the first things we noticed (and we were helped by the sunnier-than-forecast conditions) was a number of very active Beautiful demoiselles, including males trying to entice females with a fluttering wing display.

A male (note the claspers at the tip of the abdomen) Beautiful demoiselle Calopteryx virgo.

We also couldn't help but notice a much larger species flying rapidly back and forth along a section of stream, the typical male territorial behaviour of the Golden-ringed dragonfly. The length of stream patrolled depends on the density of males present as they turn back to fly the other way when another male is encountered. Although territories are generally not guarded very vigorously, aggressive encounters between males will sometimes occur when they meet - there were 3 males along this stretch and they did encounter each other more than once. They are especially active during this period of territorial behaviour and hence can be difficult to photograph, but as they occasionally pause on vegetation, patience is generally rewarded.

Golden-ringed dragonfly Cordulegaster boltonii hanging from a twig.

Of the 14 species recorded (the list, including scientific names, is below), one is a rarity in Britain, associated largely with central southern England (though it is widespread in continental Europe), and that is the Southern damselfly. It is found mainly in slow-flowing base-rich ditches and streams in acid heathlands (and also in some of Hampshire's chalk streams, one of which is about 500m from where I live despite being urban-based, lucky me!), and seems to be limited by needing water which is stable in temperature, rarely dropping below 10^oC, clearly a potential limitation during winter. However, at Crockford, numerous individuals were seen, including (again, a little patience was required) some that would tolerate a human presence near enough to see the 'mercury' mark that distinguishes it from other blue damselfly species.

Southern damselfly Coenagrion mercuriale showing the identifying 'mercury' mark near the front of the abdomen.

More importantly, active breeding behaviour could be seen - I have witnessed this before in the Southern damselfly, but never in quite such large numbers. The photograph below shows three pairs at different stages of mating. On the left, a pair which is unattached (and may simply be resting on vegetation), on the right, a male has gripped a paler female with his claspers, and at the top, the typical 'mating wheel' arrangement seen during copulation. It's not often an opportunity for a shot like this comes around...

Three pairs of Southern damselfly Coenagrion mercuriale

Of course, it's easy to get a little spoiled and forget that despite the numbers seen during the Dragon Hunt, this is actually a rare species in Britain and is covered by a UK Biodiversity Action Plan as well as being listed in Schedule 5 of the Wildlife & Countryside Act 1991 which prohibits handling without a licence.

Looking at the day's records as a whole, what does it say about the Odonata community in the area we visited? Well, it's only a snapshot, but a fair number of species were seen even though a few that I expected to see were not noted (this doesn't mean they weren't there of course) such as Emerald damselfly (Lestes sponsa) and Red-eyed damselfly (Erythromma najas). On the whole, the blue damselfly species were reasonably abundant along with the darters and skimmers (Libellulidae), but the red damselflies were sparse, as were the large hawker dragonflies (Aeshnidae) with just two Emperor dragonflies and a single Migrant hawker seen. Is this a real effect of poor weather? Well, without a more systematic study, it is of course impossible to tell for certain, but as Corbet & Brooks (2008) note using various examples (and noting the need for targeted study), Odonata are temperature-limited, so it seems likely that some impact might occur. However, volunteer records such as those here can only help to build up a picture of the current status of Britain's Odonata populations.

The day's Dragon List

Azure damselfly (Coenagrion puella)
Beautiful demoiselle (Calopteryx virgo)
Black-tailed skimmer (Orthetrum cancellatum)
Blue-tailed damselfly (Ischnura elegans)
Common blue damselfly (Enallagma cyathigerum)
Common darter (Sympetrum striolatum)
Emperor dragonfly (Anax imperator)
Golden-ringed dragonfly (Cordulegaster boltonii)
Keeled skimmer (Orthetrum coerulescens)
Large red damselfly (Pyrrhosoma nymphula)
Migrant hawker (Aeshna mixta)
Ruddy darter (Sympetrum sanguineum)
Small red damselfly (Ceriagrion tenellum)
Southern damselfly (Coenagrion mercuriale)

More about dragonflies...

If you are interested in identifying the Odonata of Britain and Europe, the following books are all excellent (there are others, but these are my personal favourites):

Brooks, S. (2004). Field Guide to the Dragonflies and Damselflies of Great Britain and Ireland (revised edition). British Wildlife Publishing, Gillingham.
Cham, S. (2007). Field Guide to the Larvae and Exuviae of British Dragonflies. Volume 1: Dragonflies (Anisoptera). British Dragonfly Society, Peterborough.
Cham, S. (2009). Field Guide to the Larvae and Exuviae of British Dragonflies. Volume 2: Damselflies (Zygoptera). British Dragonfly Society, Peterborough.
Dijkstra, K.D. (2006). Field Guide to the Dragonflies of Britain and Europe. British Wildlife Publishing, Gillingham.
Smallshire, D. & Swash, A. (2004). Britain's Dragonflies. WildGuides, Old Basing.

...and the New Forest

Brock, P.D. (2011). A Photographic Guide to Insects of the New Forest and Surrounding Area. Pisces, Newbury.
Tubbs, C.R.. (2001). The New Forest: History, Ecology & Conservation. (2nd ed.). New Forest Ninth Centenary Trust, Lyndhurst.

References

Corbet, P. & Brooks, S. (2008). Dragonflies. HarperCollins, London.
Li, J.-K., Nel, A., Zhang, X.-P., Fleck, G., Gao, M.-X., Lin, L. & Zhou, J. (2012). A third species of the relict family Epiophlebiidae discovered in China (Odonata: Epiproctophora). Systematic Entomology 37(2): 408-412.