Watch out for Gold Swifts! Especially in the daytime!
John RG Turner
Have you seen Gold Swift moths flying in the day? Probably not, but if you do, we would like to hear from you.
We are particularly interested in observations from butterfly-watchers. Moth-lovers may also take part (of course), but you do not have to be one, or to be able to recognise the colour pattern of a Gold Swift, or even to have any idea what they might look like. Their flight is unique and unmistakable, and in fact it’s much better not to catch the moth to check it, but to leave it alone and see what it does!
This species typically flies in the twilight, usually for around a half hour to an hour, between 45 minutes before to 25 minutes after sunset (though sometimes earlier or later). Probably not many people have seen it, because this time is too late for butterfly-watching, and a tad early for moth people: in fact most of us are probably at home eating dinner or watching the TV! There is also a very brief flight in the morning gloaming (around 2 am BST!) which probably very few people indeed (less than half a dozen in the UK) have seen.
But occasionally, it can be seen flying in full daylight, and the question we are asking is “Is this commoner than the experts imagine?” The behaviour is widespread, being reported from the Highlands, Yorkshire, Austria and European Russia (Yaroslavl’, about the same latitude as Golspie), but only around five times all told. But is it really so rare, or are we just missing it?
What to look for. The moth is unmistakable, as it does not buzz around looking for food—no mouthparts!—but flies in a unique way, as if it were attached to the end of an imaginary pendulum, or if you prefer, on the end of an invisible thread, swinging from side to side over more or less the same piece of ground. The swing is one or two feet in amplitude, and each swing takes a bit less than a second. The moth is a warmish brown colour, and the size of a small bumblebee.
Where? The species is quite widespread in Scotland (maps in the Provisional Moth Atlas, or on-line at http://eastscotland-butterflies.org.uk/mothflighttimes2013.html and then it
is the fourth species down on the list), and the general habitat is woodland clearings, edges and rides, river banks, damp moorland, bracken-covered slopes, usually near to trees. It is often seen around bracken, or hogweed, or among stands of rushes in the damper places.
What time of day? This is up for grabs: the only observations where the time was reported were around 3 hours after local noon (say about 4 pm BST), but this may be pure coincidence. Perhaps they are out there at 9 am!
Which month? The flying season is likely to be from the beginning of June (but at least in the Highlands from the middle of June) up to the very end of July, but over- and under-runs are as always a possibility, especially considering the way the seasons have been playing up recently!
What you are likely to see. One or more male moths—up to half a dozen perhaps in a little swarm—maybe just a solitary moth, a foot or two above the vegetation, doing the pendulum trick (“pendulating”). They may keep this up for ten minutes or so, and then may settle with their wings folded or spread out, somewhere near the top of the local plants, perhaps on the stem of a rush. If you are very lucky, you may see a female come in and a mating take place, or you may see a couple of males start to fight (!) by buzzing each other.
A point for moth-watchers. Of course, there is one other moth which does the pendulum trick: the Ghost Moth. But there is obviously no potential for confusion, as this is a brilliant white colour, and flies only in the late evening gloaming. And incidentally, swinging from side to side is an aerodynamic impossibility, and the effect is merely a very persistent optical illusion. You may just be able to see what the moths are actually doing, but it’s very difficult!
What to report.
Essential: place (plus grid reference to any precision you can manage, up to the full GPS reading).
Essential: time of day. Can be GMT or BST, but please report very clearly which you are using!
Essential: was the moth pendulating?
Essential: your contact details.
Optional extras (we’d like any you can do)
How long things continued (if you stopped to watch)
Weather (sunshine, sun with clouds, overcast bright, overcast dull, drizzling, gae dreich)
Moths doing anything else? Like perching, fighting, flying off somewhere else, mating.
If you see them late in the day of course, up to and including the sunset period, we would still like to hear from you. If you spot the elusive dawn flight, you can nominate yourself as a member of the exclusive early-bird-moth-spotters club!
Where to send. By email to John Turner at firstname.lastname@example.org
Editor's Note: You can see a short video clip of the 'pendulating' motion of the Gold Swift moth at the following link on Facebook (you don't even have to be signed up on Facebook to be able to see this video):