Here be Dragons... and Damsels

For the last couple of years I have become particularly

interested in Dragonflies. Who wouldn't be?! 

They are brightly coloured, fast flying, 

hyper-aggressive aerial predators - what's not to like?

If that isn't enough how about that fact that the best time to see them is summer, when the sun is shining, it's nice and warm and there isn't too much wind - also known as a perfect summer day? Or the fact that because there are only 40 or so breeding species in the UK its relatively easy to learn about them and have a good idea of the entire range of species (compare for example with something like 2500 moth species or 4000 beetle species or even the 500 + bird species in the UK), which means your friends will think you are an expert? For me a real draw is that you can get some great photographs of them with simple cheap photographic equipment, all of the photo's here were taken on a relatively cheap (less than a top notch smart phone) bridge camera - no DSLR, no £10,000 pound lens or carbon fibre tripod. Every bit as exciting in many ways as an elusive bird of prey, but easier to find, much easier to watch, much easier to photograph. And they have cool names. Now give me one excuse not to love 'em?

Male Common Darter (Sympetrum striolatum).

Of course I am fascinated by other wildlife too, including birds of prey: you will see (if you have a look) that one of my 'Bucket list' items is in fact to watch a Hobby hunting dragonflies, something I haven't managed yet. But anyway, back on topic...

As a result of this relatively recent fascination they took up a disproportionate chunk of my summer nature watching trips, and a correspondingly large proportion of my summer photographs. This year I didn't have as many opportunities as I would have liked because of work commitments, but I still managed the occasional sneaky trip out. My favourite spots didn't seem to have quite the numbers I remember from the last couple of years. Although this may be down to the conditions on the days I was able to visit not being ideal, end of summer weather summaries do suggest that we've had a cooler and wetter summer than average, but only by a bit.

Male Southern Hawker (Aeshna cyanea) in flight.

I'll keep an eye out for dragonflies where ever I go during the summer but to get my fix I head to a couple of pools on the northern edge of Cannock Chase. For those unfamiliar with Cannock Chase it is a Area of Outstanding Natural Beauty (AONB) between Stafford and Cannock, only about 25 miles as the Dragon flies (sorry, that wasn't very funny) north of Birmingham. Comprising largely of heathland and woodland (including large swathes of commercial coniferous forestry plantations) it certainly earns its title as it truly is a beautiful area. The two pools I visit most often are both very acidic, dark water from the peaty heathland soils, fringed with rushes and cotton grass. Both are nice and open, getting plenty of sun: one in a marshy depression on a heathland plateau, the other in an open glade on the edge of a forestry block. 

Male and female Common Darter (Sympetrum striolatum)

On a really good day I could sit for hours on the margins of these pools and watch the action, and what action! You can hear the collisions from the other side of the pool, wings rustling like carrier bags as they collide in mid-air, then swivel seemingly on the spot to do it again. Whoever nick-named aerial combat 'Dog-fighting' had clearly never seen Dragonflies compete for territory or a mate! - although 'Dragonfly-fighting' just doesn't have quite the same ring to it I suppose. It's no wonder that you frequently find individuals with damaged wings, although I have seen several with fairly large chunks missing which seem to fly without issue.

Male Four-Spotted Chaser (Libellula quadrimaculata)

On a particularly excellent day, I think 2 years ago now, I saw something like 13 species, maybe even one or two more. Certainly getting into double figures won't be unusual. Some of those species were there in their dozens, even some of the larger species. There were at least 5 or 6 Brown Hawker (Aeshna grandis) females ovipositing (egg laying) simultaneously on the main portion of the pool which is smaller than some large living rooms I've been in.

Female Common Darter (Sympetrum striolatum) foreground; Female Brown Hawker (Aeshna grandis) background.

Add to these the Southern Hawkers (Aeshna cyanea), Common Hawkers (Aeshna juncea), Four-spotted Chasers (Libellula quadrimaculata), Broad-bodied Chasers (Libelula depressa), Common Darters (Sympetrum striolatum), Ruddy Darters (Sympetrum sanguineum) and Black Darters (Sympetrum danae) and the occasional Emporer (Anax imperator) and Migrant Hawker (Aeshna mixta) it's a busy and colourful scene.

Males Azure damselfly (Coenagrion puella)

I suppose I must mention the damsels too because while they may not be as spectacular in flight as their bigger, brasher, bolder, bolshier cousins they are every bit as colourful! At that pool I mentioned it wouldn't be unusual to see Common Blue (Enallagma cyathigerum), Blue Tailed (Ischnura elegans), Azure (Coenagrion puella), Large Red (Pyrrhosoma nymphula) and Emerald (Lestes sponsa) damselflies without changing spot once.

Immature Male Black Darter (Sympetrum danae) - this one with an missing forewing, don't think he's going anywhere.

Both of these pools are isolated from any other water course: this has both advantages and disadvantages. It means they have no fish which is important for Odonata (Dragonflies & Damselflies) because fish are a key predator of their nymphs, which are all aquatic. No fish equals lower predation equals higher success rate equals more adult dragonflies equals more breeding attempts equals, ultimately, a stable population. Happy days. 

Male & Female Large Red Damselfy (Pyrrhosoma nymphula)

Not having a consistent in-flow of water also means these pools are at risk of drying up entirely in dry periods, and last year one of 'my' pools did. This poses an issue because dragonflies over winter as nymphs and so need that water to make it through to emerge as adults the following year. No water means no nymphs, means no adults from that pool. This doesn't necessarily spell total disaster, not for the pool as a habitat anyway, because dragonflies are well known to disperse massive distances, by invertebrate standards, from where they themselves emerged. Damselflies are a bit more conservative in their emigration, but some species will still travel reasonable distances.

Female Emerald Damselfly (Lestes sponsa)

We're now in the quiet period of the year for invertebrates (Boo!!), with the Dragonflies amongst them. Shame, but part of the excitement of our seasonal species is surely that we don't have them all year round? Absence makes the heart grow fonder and all that. Missing them for 6 months or more makes it all the more exciting when they do start to emerge again in the late spring and summer! So here's looking forward to the Dragons emerging next year.

Richard

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WARNING: Real science coming up

NB: A while back I read an interesting paper about monitoring wetland habitats for Odonata  and writing this made me think about it and revisit it.

Essentially, Raebel et al. (2010) were arguing that by focusing survey efforts on adult Odonata a false picture of habitat suitability or quality was being generated. They stated that even when females are observed and recorded ovipositing there is no guarantee that those eggs will hatch and develop and ultimately be successful. As dragonflies can disperse over large distances as I mentioned above, those adults present could have come from far afield, with none actually having originated in the site being surveyed. They further argued that even by conducting larval stage surveys the true picture isn't revealed because nymphs will be present in habitats were they cannot or will not make it to maturity. The only way to get a true impression of habitat suitability, they claimed, was to survey for exuviae (the 'empty casing' left over after a nymph has emerged) as this was the only way to be sure that a species had completed its breeding cycle in that location.

Very recently emerged Four-spotted Chaser (Libellula quadrimaculata) perched on its exuviae.

It made for interesting reading but wasn't without its critics, Bried, D'Amico & Samways (2012) countered that while adult only surveys may result in a positive bias indicating a higher number  of species had successfully bred, exuviae only surveys had the opposite results, a negative bias under-representing the reality of successfully breeding species. This is large part is due to the time sensitive nature of exuviae, with a very narrow time window to find them, and the effort to find them being both more disruptive and far more time consuming.

Again, very interesting reading, if you want to read up on either of these papers the references are below and both can be found on Google Scholar without having to pay.  

Papers referred to:

Bried, J. T., D’Amico, F. & Samways, M. J. (2012) A critique of the dragonfly delusion hypothesis: why sampling exuviae does not avoid bias, Insect Conservation and Diversity, 5: 398–402.
Raebel, E. M., Merckx, T., Riordan, P., Macdonald, D. W. & Thompson, D. J. (2010) The dragonfly delusion: why it is essential to sample exuviae to avoid biased surveys, Journal of Insect Conservation,  14: 523–533.