Saturday, 21 December 2013

One Out, One In ?


Almost the end of the year now, and just time for a review of this year’s records before they’re sent off to the BDS.
I always go back over records I’m not happy about at the end of the season and review the photographs I’ve taken, and just two to clear up this year but they’re both potential biggies:

First I belatedly claimed an Azure Hawker at Loch Garten after discovering the female has a brown and blue form which tied in with a sighting I couldn’t identify at the White-faced Darter site. I’ve since discovered that Common Hawker also has a similar brown and blue form which is much more common in Scotland than it is in England, and taking into account the size of the dragonfly in question (on reflection it was too big to be an Azure) plus the fact Azure Hawkers have not been seen here for a number of years, I am striking it from my list for the year (The Birdman can relax as he didn’t see it anyway).

Azure Hawker female brown/blue form

Common Hawker female brown/blue form
 
My second review was way back on June 30th, when I recorded my first hawker of the year at Milkwellburn Woods.
It was flighty and difficult to ID though I eventually called it as a common hawker male due to the markings, though size and jizz was puzzling to say the least. I put my bafflement down to the simple fact it’s been so long since I saw one I just didn’t have my eye in yet, but when I saw my first proper common hawker male a couple of weeks later I realised it had been a mistake to call it, leading me to do some serious investigation and research to pin down its true identity.

I was out with the Birdman in Milkwellburn woods (same day we got the female Broad-bodied Chaser) and we were making our way down a fairly steep woodland ride when I spied a dragonfly hawking a clearing in the distance, wings glinting as they caught the sunshine.
When we got there it was still hawking with a rapid to and fro action about head height. Unusually I couldn't make out any markings as it zipped about and my first thought was that it was very small for a hawker. The profile view we were getting gave the impression of a very short and rather stubby looking dragonfly, in fact it resembled a flying half-smoked cigarette I recall thinking. The strong sunlight at the time wasn't helping with the ID either, but I can safely say early impressions had me totally baffled.

When at last it came below head height and briefly towards me I was able to confirm a 'mosaic' hawker pattern along the top of the abdomen which just looked pale/white due to reflecting light (though I'm sure I got a flash of pale blue from somewhere as it passed me), and antehumeral stripes at the front of the thorax (though there is a question mark next to this in my notes).
These features led me to conclude it must be a Common Hawker male, though the size and jizz was odd to say the least, but like I said I put that down to the fact I didn't have my eye in yet as it was the first hawker of the year, and thought I was just misjudging/misremembering size after an absence of some 8 months. 

Eventually (after acquiring a meal mid-air) it alighted on a tree trunk quite high up giving an angled side-on view. I had to back off to get a better angle as it hung vertically but in strong light I still wasn’t able to clearly see any recognisable markings along the side of the abdomen, and strangely the thorax appeared to be wrapped in some sort of reflective web so I couldn't make out any pattern there either, which again I put down to an effect caused by the strong sunlight.
It appeared quite settled now so I was able to go for my camera, but (as luck would have it) just as cloud cover came, and with it a strong gust of wind which lasted for some seconds and took the dragonfly away. We waited a few minutes but with the sun now in the clouds it wasn't to reappear in the blustery wind. 

So that was that. I called it in as a Common Hawker but made notes at home and kept those mental images with me until I saw my first 'proper' common hawker about a fortnight later, when I realised immediately that this dragon hadn’t been what I called it as, as these were obviously much bigger and not at all like what I'd seen in Milkwellburn Woods.

The woodland clearing in Milkwellburn Woods
Front is a dried-up boggy area, the pale tree towards the right
is where the mystery dragon landed before the wind took it
 
Since then I've done much research, and having explored every aspect of the sighting concluded that the true identity of this dragonfly must be a Brachytron Pratense; a Hairy Hawker, which would be a bloody good record for Gateshead as only a few historical records (of wandering individuals) exist :O
In fact looking at previous records and distribution maps for the species, the only records for the Derwent Valley are pre-1974 (from BDS historical maps and Corbet & Brooks historical distribution maps). But as a species it is certainly spreading north, already colonising Dumfries and Galloway in the west, and in the east more recent records exist from Cowpen Bewley, Durham City and Warden Law near Sunderland, as well as a scattering in Northumberland.

The fact I’ve never previously seen a Hairy Hawker in the field meant I have nothing to compare it with, (and finding one in a woodland ride would point to it being a female), but my conclusion comes after much reading of species accounts and viewing images and video-clips, as bit by bit it all began to fall into place :

The fact I described it as a flying cigarette stub; Literature says they don't have a waist like other hawkers and so look cylindrical in flight (ticks box)
I also read that markings on the abdomen aren't easily made out unless you get a really close view (ticks that box too)
The patchy descriptions of markings which caused me to call it as a common hawker (mosaic abdomen, hint of pale blue, antehumeral stripes? are all consistent with hairy hawker (tick, tick, tick)
The thorax is covered in hairs (hence the name) which explains the effect of the reflective light webbing I got when it was perched on the treetrunk (another tick)
The size - man it was really really small (tick) indeed it's the smallest hawker at an average of 55mm almost a whole cm shorter than migrant.

And the process of elimination:
Basically, having observed many hawkers of our three resident mosaic species this summer I am positive this was not one of them. It was far too small for common or southern hawker, and far too soon for a migrant; on jizz alone I should have realised it was a dragonfly species I hadn't seen before, so with all things considered, I can be 100% certain what it wasn’t, but can I be 100% certain what it was?

Hairy Hawker
Will you make my Gateshead list?
 
Well it’s six months since the sighting was made but actually I reached this conclusion not long afterwards. I've gone through it all again and looking back I don’t think it could have been anything else, but there's always the niggle on conclusions made after the event of "What if I'm remembering it wrong?" (there is a blur over the presence of antehumeral stripes) and it’s a fact of life that without photographic evidence, records of this nature (improbable but not impossible) are generally dismissed these days, so on my record submission it will go down as a probable (with much notation).
And I won’t be putting it down on my Gateshead or year-list just yet, but the little bugger is etched in my memory and when I actually see one in the field at a known site; then I will know for certain and tick it retrospectively (or otherwise).
I doubt it would be an indication of a nearby colony anyway, most likely just a one-off wanderer (females can be found in woodland some kms from the nearest habitable water-body), so in the scheme of things not a record of great importance (like the Gibside Golden-ringed  of 2010), just a great personal record, but I’ll certainly be checking the area next year just in case ;)

Roll on next spring! (again)

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