Half Century Of Long-tailed Blues
On Sunday morning I received a number of messages that Mark Colvin had found a male Long-tailed Blue at Brighton Racecourse, which was being enjoyed by a growing number of visitors, some of who had travelled a long distance.
This was the first county record for November, but not for the UK; the national record being held by a 20 November 1961 sighting in Devon (per Richard Fox, BC). A second sighting by Katrina Watson subsequently proved to be the same individual, based on photographic comparisons.
With a busy domestic schedule I was too short of time to make it over to the racecourse, so had to make do with a trip to my nearest site at Lancing Station (scruffy area adjacent to the north side car park). Time was running short and in the cool, foggy conditions I was giving up hope.
While discussing the Brighton sightings on the ‘phone with Mark, the sun briefly forced its way through, and at 1.35 pm a small patch of bright lilac-blue magically appeared on the bramble in front of me! This gave me the greatest of pleasure, being my 50th (minimum) individual Long-tailed Blue in the UK.
After taking a few shots as the insect warmed up and became mobile, it disappeared northwards over the concrete wall into Sompting Road. I thought that was it, but as I walked out onto the road I saw it flying E – W and then land at the near end of a concrete driveway. It sat here and sunbathed for a few minutes, before heading up over the roof and disappearing. I only had a further 5 minutes available, so never saw it again.
Summary
A number of interesting stats are coming together. When looking at the ratio of sexes recorded during the British brood, the same pattern has emerged as that seen in 2013. Females have emerged before the males, which is of course the reverse of the pattern observed in most species.
Sussex data
19.9.15 – 25.10.15 female:male = 8:3
26.10.15 – 1.11.15 female:male = 2:5
In
2013 the British brood females were invariably photographed in perfect or near-perfect condition, and seldom repeatedly (if ever) in a state of gradually degenerating condition. However, many of the males were photographed over the course of a number of days, demonstrating increasing wear and tear. The insects behaved in a colonial manner and mating was observed – but no egg-laying. Circumstantial evidence suggests that the females may have migrated south soon after mating, whereas the males hung around, presumably hoping to grab another virgin.
In
2015 the British brood has been found and photographed only in perfect or near-perfect condition, irrespective of sex. No colonial behaviour has been observed and only in rare cases has the same individual been photographed on more than one day, always when poor weather would have grounded them. In fair weather, the butterflies have consistently disappeared shortly after midday. Circumstantial evidence suggests that all of the butterflies, irrespective of sex, may have migrated south soon after emerging. The emergence has been later than it was in 2013, apparently due to the slower development of early stages in much cooler conditions. Day length and temperature may have triggered this markedly different behaviour in the emergent adults.
I have now collated a 2015 total of 36 Long-tailed Blues in Sussex, although Colin Pratt has used a slightly different method to achieve a total of 37. I also have a UK total of 62, but this is an underestimate, based on the assignment of just 1 per day, where Kent birders recorded presence/absence on a site, rather than numbers.
Bearing in mind the method of counting during the 1990 event (which included a large number of recounts of the same individuals), I believe that 2015 has seen the second largest ever Long-tailed Blue event in the UK.
Recording effort has been very much focused on Sussex, and it is quite possible that the national picture has been less well recorded than it was in 2013. Had poor weather not stalled the influx through a large part of August, I suspect that the story might have been different.
It is exciting to think what future years may hold for South Coast butterfly enthusiasts.
You make your own luck
Goldie