Dragonflies and Damselflies
The common hawker or Aeshna juncea is the most numerous and widespread of the ‘big dragons’ in Orkney. Nevertheless, apart from on the island of Hoy, breeding has only been proved at one other site. This was at a man-made pond in Stenness, just over half a kilometre across the Sounds from Hoy. Egg-laying was witnessed in 1997, but this was the only year breeding was proved, despite some insects being seen there over the following several years. They are known to breed in forty, one-kilometre squares on Hoy from The Kame, south to Melsetter, with breeding suspected in another nine squares.
This large hawker is a fast, powerful and a seemingly tireless flier. It disperses widely, perhaps in the search of new breeding sites and this is reflected by the fact that there have been 18 records of this insect away from their breeding areas, including two sheltering in the Gloup, at Halcro Head late in 2008; one caught in a mist net in Holm in 1982 and another on its last legs in the Flotta Oil Terminal in October 1986.
Breeding for this impressive black and gold dragonfly is confined to the parish of Hoy. The eggs of this, the largest of Orkney’s dragonflies, are laid in moorland burns rather than in standing water. Breeding has been proved along the burns of Berriedale, Rackwick, Trowieglen, Nowt Bield, Red Glen, Whaness and the South Burn. Apart from on Hoy, one of these magnificent insects was claimed to have been seen between Heddle and Grimbister on West Mainland, in 1999.
First discovered by the author in 1984, the 4-Spotted Chaser or Libellula quadrimaculata is a squat, medium-sized dragonfly that has only been proved to breed in one lochan cluster, below the Rinnigill Burn on the Moss of Whitestanes, Hoy. This is surprising, as in other areas of Scotland, they breed in a wide range of acidic habitats, apparently similar to many lochans on Hoy and elsewhere. Specimens were seen during two summers at one such pool, behind the Rackwick car park, but breeding was not proven; that is, no flies were seen in tandem or egg-laying. Neither were any exuvia (the empty larval cases) found. There have also been records from along the South Burn and Trowieglen. Although quite close to the known breeding site, breeding at these sites was never proven. Nor was the record of a single insect along the Burn of Ore in 1999, some seven kilometres to the south.
The black darter or Sympetrum danae has been a remarkable success story in Orkney in recent years. Prior to 1996, it was known only in the island of Hoy, where breeding has been proved in eleven one-kilometre squares and suspected in a further nine. However, in 1996, they bred at the man-made pond in Stenness (see common hawker above), and have bred successfully in every season since then. This species is known to be a wanderer, which undertakes migratory journeys and is capable of traveling considerable distances, so perhaps it is not too surprising that it spread from Hoy. What is surprising is the speed at which new and widespread sites have been colonised. In just fourteen years since first breeding away from Hoy, there are now established breeding sites in seven one-kilometre squares on the West Mainland with a further six possible sites, one on the East Mainland and two or three on South Ronaldsay. In 2008, there was a record from Rousay but breeding was not proved. It is only a matter of time before they become established on one or more of the more northerly islands in Orkney.
The lesser emperor or Anax parthenope is a southern European species and a rare migrant to Britain, the first record being in 1996 in Gloucestershire. Since then it has established a breeding toehold in the extreme south of England. How remarkable then that the first ever Scottish record should be on Sanday. A live male was found on 19 June 2000, but sadly, died shortly afterwards, no doubt exhausted from its astonishing journey.
The large red damselfly or Pyrrhosoma nymphula is the most common and numerous of all seven species of Orkney’s breeding Odonata. It is almost always the first to emerge, usually in late May or early June. In fact, the emergence date appears to be getting earlier. It lays its eggs in ponds, ditches and acid bogs, the latter habitat certainly being preferred in Orkney. It has been recorded as breeding in fifty, one-kilometre squares on Hoy; thirty-three plus six suspected squares on the West Mainland, ten plus two suspected squares on the East Mainland and in six on Rousay. There is a possible breeding site on Burray but surprisingly, there are no records from South Ronaldsay. Perhaps the paucity of acidic sites on most of the North Isles excludes this species from breeding there, although high acidity does not seem to be a prerequisite elsewhere.
The common Blue Damselfly or Enallagma cyathigerum is the only species which breeds in Shetland, so it is obviously well-adapted to the northern climate. In Britain as a whole, this species occurs in a great variety of habitats, including, quarries, lakes, ponds, lochs, slow rivers and canals, in both alkaline and acidic conditions, at a broad range of altitudes and on water-bodies varying greatly in size.
For these reasons, the distribution within Orkney is very odd indeed. Not surprisingly, it has been recorded in thirty-four one-kilometre squares on Hoy. There are also records from five squares on Rousay and single sites on the East Mainland, South Ronaldsay and Egilsay. There is a suspected site near the north tip of Sanday, but there are no records from any of the other islands. Even more surprising is the fact that breeding has been proved at only two sites on the West Mainland, at the RSPB Reserves of The Loons and Loch of Banks, Birsay. There are another seven possible or suspected breeding sites.
Although not often numerous and with far fewer breeding sites than the other two damsels, the blue-tailed damselfly or Ischnura elegansthis, is the most widespread species in Orkney. As well as breeding on the West Mainland (thirteen proved sites plus five possible), the East Mainland (four proved sites plus two possible), and Hoy and Walls (six proved sites plus five possible), there are breeding sites on another five islands: Graemsay (one), South Ronaldsay (four proved sites plus one possible ), Egilsay (two), Papa Stronsay (one) and Sanday (one proved site plus two possible). It is therefore the most northerly of Orkney’s breeding species. Perhaps the fact that the blue-tailed can tolerate a degree of brackishness and pollution explains why it can colonise such salt-laden sites as the flat, alkaline island of Sanday.
From the above accounts, it is obvious that there is great scope for any ardent dragonfly hunters to add new records for most species in Orkney. The author requests that especially on warm, calm days, when you see dragonflies on what look like suitable breeding sites, you tarry awhile and attempt to prove that they are breeding. Look for flies in tandem (joined together: the male gripping the female behind the head with his tail claspers) and ovipositing (egg-laying), or examine emergent vegetation for exuvia, the beautiful, semi-transparent larval cases left behind after the adults emerge. Please send as much information as possible. Rather than just reporting 20 damselflies, please record how many were in tandem and whether you saw them laying eggs. Some species attach their eggs onto vegetation, whilst others simply flick the eggs into the water. The name of the site (preferably with a six-figure map reference) is essential and any other information that you think relevant or interesting.
© Keith Fairclough.
Orkney Dragonfly Recorder