Tuesday, 25 July 2017

Dragon Hunt

Within Orkney, there are only eight breeding species of dragonfly and damselfly, four of each. All eight species occur in Hoy, the island to the south west of mainland Orkney, but no other island of the archipelago has the full assemblage. None of the species are rare in a UK context, but one, the Four-spotted Chaser, has a very local distribution on Hoy and appears to be confined to a few pools in the Rackwick valley.

In 2014, no records were received for Four-spotted Chaser. In 2015, only one exuvia, the shed larval skin, was found. This, at least, proved that one had emerged to be an adult insect. Last year, 2016, there were no recorded sightings of the species on Hoy, raising the question "Are they still there?"

It appears that there is only a small population, so it might be that, as the dragonfly has a two year life cycle (perhaps longer in a harsh environment), flying adults will only be seen every two years. In this scenario, the 'missing' years being explained by the fact that the larvae are only half-grown. Equally, as the pools are not readily accessible, it may just be that lack of recorder effort is the reason for the dearth of sightings. Having not seen a Four-spotted Chaser in an Orkney context, I was keen to see if they were present in 2017. An added complication to surveying for dragonflies, especially in Orkney, is the presence of breeding Red-throated Divers on many of the same pools that the odes use. The level of protection (Schedule 1) afforded to these divers means that a licence has to be obtained to approach them during the breeding season.

It is also possible, though perhaps unlikely, that the Red-throated Divers on Hoy are predating the Four-spotted Chasers, either as larvae or as emerging adults, on the pools which they share. Having liaised with a Field Club colleague who possessed a Schedule 1 licence, it still remained necessary to find a convenient date where we were both available and also when the weather was suitable for dragonflies and surveying.

The chaser's flight season within Orkney begins in mid-May and lasts until mid-August, with the peak time being mid-June until the end of July. As this time ticked by, it began to look as though we might miss the opportunity for another year. But this does rather suggest that recorder effort is the problem! Fortunately, several days before National Dragonfly Week commenced, all the planets aligned and the Hoy trip went ahead. Hours before setting off, we learned that the divers on site had failed in their breeding attempt for this year, which took away a bit of the pressure we were feeling.

Once on Hoy, a local minibus dropped us off on the nearest bit of tarmac road to the pools in question, then it was a yomp across country, very off piste, over heather, bogs, burns and hills. En route, we saw several Large Heath butterflies, which I mistakenly presumed were day-flying moths until I was educated otherwise. At the pools, there were many damselflies on the wing, the day being very sunny and with a gentle breeze. An immature Black Darter dragonfly was seen, then we discovered an emerging Common Hawker, hanging beneath some heather at a pool edge.

The Admiral busy logging all Odonata activity

Common Blue Damselflies in tandem

Blue-tailed Damselfly female, form rufescens-obsoleta

Recently-emerged Common Hawker

Our guide pointed out another dragonfly, whizzing low over the water, which soon resolved itself into a Four-spotted Chaser. So they were still present! Yay! Then we spotted another and another.

Four-spotted Chaser, with minimal wing damage

Four-spotted Chaser, with quite a bit of wing damage
We did not witness any breeding activity, and our photographs from the day can only confirm that two of the chasers were male, so there's a bit of a question mark over the future. Hopefully, our brief snapshot of their flight season is not typical, and sufficient numbers of males and females made it onto the wing and were able to mate. Pond dipping for larvae would be an option, but I think it would fall foul of the Red-throated Diver issue.

Returning to the ferry on foot, we popped into another site and found evidence of Emerald Damselfly emergence, meaning that on the visit to Hoy we had seen seven of the eight Orkney species. A good day's work.

All photos courtesy of Alan Nelson, less for the first one.

Next time: National Dragonfly Week begins...

Monday, 24 July 2017

Interlude

[Moves aside several weeks' worth of accumulated detritus, blows the dust off the 'New post' button and tentatively presses it...]

It has been nearly three weeks since my previous blogpost, which means that my usual 'twice a week' habit has foundered on the shores of the unchartered island of Doingotherstuff.

And what other stuff have I mainly been doing? Well, it's been quite an intense period of odo-ing, brought about by a decision made months ago to celebrate National Dragonfly Week (15-23 July) with a tour of the smaller islands of Orkney. The plan was to raise the profile of dragons and damsels throughout the outer isles, so that more folk might take an interest in conserving their habitat and to generally look out for these wondrous insects.

As a member of the Orkney Field Club committee, I was also keen to give some time to folk on the outer isles, because most Club walks and talks tend to be Mainland-based. So here was my opportunity to put that right and perhaps collect some useful data along the way.

I would have to take the time off work for the duration of National Dragonfly Week, but there would not be a possibility of recce-ing each island beforehand. To overcome this problem, I approached either Island Rangers or nature reserve wardens (RSPB) on individual islands to act as hosts and provide some logistical support, mainly in the form of transport. As a self-funded venture, I tried to keep costs down by not taking a car to each island. The wardens and rangers were keen to be involved, so the week's itinerary soon filled up and we then publicised the events. Through the Field Club network, via my own OrkOdo page on Facebook and with flyers sent to each island, the visits were promoted from about two weeks in advance.

I already had a prior commitment on Saturday 15th July, at an open day organised by the local biological records centre, but this would also act as a promotional day for the OrkOdo tour.

The Sunday before National Dragonfly Week, we (Our Lass, The Admiral (visiting on holiday), and I) took the ferry over to Graemsay to survey a quarry pond as a shake-down trip, to iron out any possible problems. This worked well, we seemed to have all the correct gear, plus we found a handful of Blue-tailed Damselflies emerging, which proved that they were actually breeding on the island, rather than being blown in from elsewhere.

A recently-emerged damselfly with its exuvia (shed larval skin)

Our Lass, Yours Truly and Sian (from Life on a Small Island), possibly as you've never seen her before

This is what we were looking at, a female Blue-tailed Damselfly
All photos courtesy of Alan Nelson.

To be continued...

Wednesday, 5 July 2017

Pond life

A few weeks ago, on a walk with the Flora group of the Orkney Field Club, in between all the orchid wrangling and what have you, I was shown a flooded quarry that had potential as a dragonfly site. Once I discovered who was the land owner, I was fortunate enough to be granted permission to survey the site for Odonata. This afternoon, I had some free time and, more importantly, lots of sunshine!

Whilst most of the site is probably too deep for odes, there are shallows at the margins, with emergent vegetation likely to appeal to a damselfly larva looking to take the next rung on the ladder of Life.


It is also home to lots of these wee guys...



so maybe not so hospitable for insect larvae of many species?

After a few minutes of searching, I came across a Blue-tailed Damselfly, and then another and another.


There were Large Red Damselflies too.


All damsels so far, approximately 15, were mature adults, and I couldn't discount the possibility that they had flown in from elsewhere. However, just as I was retracing my steps, I spotted this very fresh immature one, pale-coloured, milky wings and not far from the water's edge. It may well have just taken its maiden flight. I think it's a Blue-tailed Damselfly, but no amount of searching could locate the exuvia from which it had emerged. So the breeding status of the site is unresolved.


I did find Large Reds ovipositing in tandem, so they are trying to breed here. Time will tell whether they are successful in that endeavour.


And whilst we're on the subject of mating, back home at Tense Towers, later in the evening, the local Hares were looking decidedly frisky.


It's not just March when they go mad, y'know.