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|
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...