Neil Hulme

[Neil Hulme]

The 2023 Long-tailed Blue Season In Sussex And Beyond

I've already posted much of the following text in another UKB thread, but it bears repeating here, as the Long-tailed Blue is reacting so rapidly to a warming climate that even Pete's latest offering (British & Irish Butterfly Rarities) will become out-of-date very soon; hard copy publications won't be able to keep pace with these changes. The real headline from 2023 was that this species, for the first time, double-brooded widely on British soil. The following notes also act as an introduction to the next few posts.

The first wave of immigrants arrived in Sussex from 29 June onward (27 June on IOW) and flew until mid/late July. Most of their progeny (first wave first brood) emerged from 10 August onward, although a few early runners emerged at the very end of July (31st) at Newhaven. This UK-born brood continued to emerge until the start of September, with the last pristine adults from this cohort being detected in a Felpham garden (1 September), on Eastbourne seafront and in a Lancing garden (2 September).

These adults (some of which shifted northward again – being seen much deeper into Sussex than usual, and across inland counties including Oxfordshire, Bedfordshire, Essex and Suffolk) produced the first-ever confirmed second brood (first wave second brood) on UK soil, which emerged from 15 September onward (as first observed at Newhaven).

Some unusually late, late-September egg-laying (e.g. up to 25th at Newhaven), might have been an attempt at producing a third brood (first wave ?third brood), but with such a complex pattern of arrivals, egg-laying and emergences, proving the successful attainment of a first wave third brood was nigh on impossible and, in any case, almost certainly doomed by the autumn weather-collapse.

The second wave arrived over the period 15-27 August. Their progeny (second wave first brood) emerged from late September onward (22 September at Worthing beach and 23 September Newhaven), peaking end-September/early October. Many of the common and widespread emergent adults reverse-migrated; a significant departure event (taking advantage of fine emigration weather) was apparent on 9 October, with a reduction in numbers at Lancing Ring from a minimum of 22 on 8 October to just 3 by late afternoon on 9th, leaving just heavily worn, elderly males. A female departed from Worthing beach in the early afternoon. However, the main exodus in East Sussex didn’t occur until a week later.

Egg laying on Spanish Broom at Newhaven on 6 October may have been a doomed attempt at producing a potential second wave second brood.

The third wave arrived from 29 August to early September and flew until mid/late September. By mid-September, the majority of primary immigrants (which hit the entire length of the South Coast this year, from Cornwall to Kent) were dying off rapidly; numbers at the Pagham beach breeding site dropped from a peak of 26 on 11 September to just five on 15 September.

The progeny of the third wave (third wave first brood) emerged from mid October onward (12 October females in Lancing and Newhaven gardens) and had the potential to continue emerging through the remainder of October and long into November. However, the last confirmed sighting of a freshly emerged third wave first brood adult was made at Pagham beach on 22 October. This pristine male was observed flying rapidly south over the shingle at 12.35pm.

There was also some evidence of a very small fourth wave, with two adults incoming at Beacon Hill (Rottingdean) on 9 October; any eggs laid by this cohort had no chance of developing to adulthood (potentially in late November and December – weather permitting).

The raid deterioration of the weather from 23 October onward, which soon developed into a prolonged period of torrential rain and storms, brought the 2023 Long-tailed Blue season to a premature close, with just half-a-dozen weary looking males appearing in rare spells of sunshine at Lancing Ring and on Eastbourne seafront between 24 October and 5 November. In captivity, adults raised on Lespedeza thunbergii at Felpham continued to emerge beyond this date. These were released, to give them the opportunity to fly south. In the wild, a huge number of early stages must have perished due the weather-collapse.

The first wave was small, the second very large, and the third larger still. The fourth wave appears to have been very small. This was the largest-ever incursion of Long-tailed Blue into Britain, and the first case of double-brooding.

Protogeny (females emerging ahead of males, which is unique among British butterfly species) was proven yet again. In one well-observed case (Newhaven garden, 15-19 September), where a batch of eggs was laid contemporaneously by a single female, the resultant adults emerged females-first in the pattern F, F, F, F, M, M, M.

I now believe that protogeny in Long-tailed Blue is a strategy to maintain genetic diversity. This species migrates in overlapping waves, so if females from a single egg batch (20-30 ova are often laid on an isolated patch of foodplants, before the female moves on) emerge ahead of males, there is a greater chance of fertilisation by an unrelated insect, rather than a sibling.

Clear polyphagous behaviour was evident in a private Felpham garden. The first wave laid all eggs on Wisteria, the second wave all on Broad-leaved Everlasting-pea, and the third wave on beans and Lespedeza thunbergii. In captivity here, a larva was successfully raised on Kidney Vetch.

Reverse migration departure times, when observed, again clustered around midday. At 12.30pm on 4 October a fresh male, which had emerged in a Felpham garden and been faithful to its small territory over the previous 48 hours, spiralled high into the sky before heading south. A male flew south from Pagham beach at 12.35pm on 22 October.

2023 Sussex Sites: There were sightings at Selsey, Pagham, Bognor, Felpham, Worthing beach, West Worthing allotments, Broadwater Cemetery, Lancing Ring, Patcham (N Brighton), central Brighton, Whitehawk Hill, Rottingdean, Newhaven town (multiple sites), Newhaven Tidemills, Rodmell, Piddinghoe, South Heighton downs, Buckle Bypass, Seaford garden, Eastbourne downs, Eastbourne seafront, Bexhill, Icklesham, Winchelsea, Rye, and further inland at Storrington, Billingshurst, Newtimber Hill, Burgess Hill and Horsham. However, as always, the majority will have gone unseen, unrecognised or unreported; the numbers of immigrant butterflies and their progeny must have been massive.

The following posts represent just some of my personal highlights of by far the best UK Long-tailed Blue season yet. I believe that this was triggered by record-breaking April temperatures in Spain, causing an earlier-than-normal northward shift of the population.

[Neil Hulme]

10 - 16 August 2023

I was too busy with work to go looking for the early-arriving primary immigrant Long-tailed Blues this year. In the past, I would have made time, but I've seen so many since 2013 (I stopped counting UK individuals at 200) that the species no longer has the rarity value it once commanded; it now clearly qualifies as a British species, being a regular migrant - just like Clouded Yellow and Painted Lady, of which I've seen fewer in Sussex over the last ten years.

However, the mint condition UK-born butterflies still excite me, so when Lindsay Morris contacted me on 10 August, to say that he'd seen one on Lancing Ring, then followed-up with a message that he was looking at a mating pair, I dropped everything and headed to Lancing Ring. Over the next week, Lancing Ring established a reputation for being one of the best locations to see the Long-tailed Blue in 2023, with up to a dozen individuals being present, including several more mating pairs. People started to come from all over the country and this continued well into October, with Lindsay performing the task of ringmaster and generously giving many guided tours.

[David M]

...it now clearly qualifies as a British species, being a regular migrant - just like Clouded Yellow and Painted Lady, of which I've seen fewer in Sussex over the last ten years.

Yes, Neil, this species is now so reliably annually that it has attained a similar ranking as Clouded Yellow.

Fascinating reportage at the top of the page. It'll be interesting to see how this develops over the years.

I wonder how long it'll be before Lang's Short-Tailed Blue makes an appearance!

[Neil Hulme]

I wouldn't place a bet on what comes next, David. There are now numerous contenders and we may get the unexpected before the expected.
BWs, Neil

[Neil Hulme]

4 - 11 September 2023

During the period between this and the last post (17 August - 3 September), the numbers of Long-tailed Blue reported daily across Sussex were generally in single figures, although they were spotted far and wide across both the West and East vice-counties. However, during this period I did gain access to the very extensive private allotments in West Worthing, where I rapidly located more than 50 eggs over just a small area; this, unsurprisingly, led to follow-up visits later in the autumn, during which I ambushed a few freshly emerged adults, although my access was completely reliant upon the presence of an allotment-owning friend. I also received a report from Tony Hill of a dozen adults at Pagham beach on 2 September, so decided to spend some time there, well away from the crowds.

I love Pagham beach; it's like stepping back in time. On the walk down to the shingle there's always the smell of soft ice-cream and candyfloss as you pass the cafes, gift shops and amusement arcades, and I got into the habit of patting the quiff of the plastic Elvis for good luck - I got plenty of that! My most productive visits were made on 4 September, when I counted 17 individual adults, and on 11 September, when I achieved my highest tally of the year with a total of 26. These butterflies were predominantly third wave primary immigrants, although there were one or two first wave first brood individuals amongst them.

There was plenty of egg-laying activity; this is not just a staging post, like the Worthing beach site (although a complete lack of nectar there, due to wind-burn, precluded a repeat of the 2022 pre-emigration congregation), but also an extensive nursery area. Broad-leaved Everlasting-pea grows widely along the back-beach, and Gorse and Broom provide alternative foodplants.

On the way home from Pagham, I stopped in to visit friends whose wildlife-friendly garden near Bognor attracts the Long-tailed Blue annually. It’s not difficult to see why, if you look at the image below. Of the three butterflies present in the garden that day, two had obliged by doing what comes naturally to this highly promiscuous species.

[selbypaul]

Thanks for writing everything up about the Long Tailed Blue migration and breeding patterns so clearly and concisely Neil. It really is fascinating how quickly things are changing!

[Neil Hulme]

Thanks, Paul. After 10 years of observing this species on British soil (with much help from many observers, most notably Dave Harris of Newhaven), all has become pretty clear. Perhaps unsurprisingly, the Long-tailed Blue's migratory behaviour has much in common with the Painted Lady, these being two of the most successful butterfly species on the planet - it was just a case of proving what's been going on, particularly since 2013.
BWs, Neil

[Neil Hulme]

26 & 28 September 2023

Having found so many Long-tailed Blue eggs in the allotments at West Worthing, and knowing how rapidly the life-cycle develops under different temperature regimes, it wasn't too difficult to predict when the adults would be emerging. I would have liked to spend more time in there, but my access was restricted to times when a friend would be visiting to work on her vegetable plot. However, I did get lucky on a couple of other occasions, when I found a few males holding territory alongside the sheltered twitten that runs up the eastern edge of the site.

One male really stood out as being particularly attractive, with unusually broad dark margins, well developed eye-spots and long tails. This individual clearly demonstrates how effective the distractionary 'false head' design can be in this species.

[bugboy]

nuff said!

[trevor]

The dark wing margins elevate an already beautiful butterfly to the level of stunning!
I was delighted to photograph a similar specimen at Lancing Ring. You'll remember that
particular day when you acted as referee to the scrum around that mating pair!

All good fun, great series of articles!

[Benjamin]

Protogeny (females emerging ahead of males, which is unique among British butterfly species) was proven yet again. In one well-observed case (Newhaven garden, 15-19 September), where a batch of eggs was laid contemporaneously by a single female, the resultant adults emerged females-first in the pattern F, F, F, F, M, M, M.

So you reckon this is beyond doubt now? I’m still finding it hard to get my head around (as detailed in my diary just now) but that prob says more about my understanding of the subject than the data!

It would be quite something to show this beyond doubt - I hoped to have my Whitehawk Hill allotment up and running for such experiments by now but unfortunately it’s still a little way off.

[Neil Hulme]

Thanks, Paul. That first image is my all-time favourite of this species.

Thanks, Trevor. I recall that magical day very well; loads of stunning butterflies, lots of lovely people and, perhaps most importantly, great fun - that's what it's all about!

Hi Ben. I'll have to be fairly brief in my reply, as my main priority is getting the entirety of the 2023 season diarised before the 2024 season kicks off. Of course proving that something happens is far easier than proving why something happens, which is ultimately a matter of potentially endless speculation and an exercise in finding a best-fit for the data. The latter is probably more suited to a discussion forum (which you can dip in and out of), rather than a diary.
Irrespective of the ten-years of observations that led me to the recognition of protogeny in LTB (I started noticing that something odd was going on as far back as 2013, and there's some coverage of this in The Butterflies of Sussex), I'll just focus on that particular F, F, F, F, M, M, M emergence sequence. This was recorded under very closely monitored conditions in Dave Harris's Newhaven garden. I view Dave as one of the best recorders and observers of butterflies in the UK (although he prefers to operate below the radar, so may not be known to many), so I have complete faith in his data. It's worth pointing out that Dave was previously a sceptic in this matter!
If I ask myself 'how often have you seen a female Orange-tip before your first male of the season?', the answer is probably twice in 55 years - but always followed by a string of males. How often has my first PBF of the year been a female? Just once, about 15 years ago, in a tiny population - it stood out as being so unusual that it has stuck in my memory; unsurprisingly, it was followed by a succession of males.
But how unusual would it be to see four female Purple Emperor or Duchess of Burgundy before seeing a male? I think the chances of observing emergence patterns such as this, generated randomly, are vanishingly small.
I've had a quick read of some of your thoughts as to why such a thing might be happening, but will have to get back with some points once I get my diary up-to-date.

BWs, Neil

[Neil Hulme]

30 September - 3 October 2023

During this period I spent many a happy hour observing the Long-tailed Blue on Lancing Ring, often in the company of Lindsay Morris. Butterfly enthusiasts were visiting from far and wide and I doubt that very few, if any, went away disappointed. Day counts hovered around the double-figures mark, reaching a dozen on 3 October, including a nice female. The butterfly was seen more widely across the site than in previous years, with plenty appearing within woodland glades just below the summit, and some as far away from the Ring as the field above the cemetery. However, many observers focused their efforts in the chalk pit, which proved to be a highly reliable area for lekking males. The daily tally for the site was usually boosted by two or three males in Lindsay's back garden, which backs onto the chalk pit.

[David M]

That individual you posted an image of on 26th February is undoubtedly the finest Long Tailed Blue I've ever seen, Neil.

When I see this species on the continent, it's rare to see a gleaming fresh one. I suppose they succumb to the regular skirmishes they have very quickly.

[Neil Hulme]

Thanks, David. It was simply perfect. I went home very happy that day.
BWs, Neil

[Neil Hulme]

4 - 9 October 2023

This period saw a continuation of the Long-tailed Blue festival on Lancing Ring. On 4 October, I started the day at Pagham beach, where a modest 6 adult males were patrolling over the extensive stands of Broad-leaved Everlasting-pea. On the journey back to Lancing Ring, I stopped off briefly at a friend's garden near Bognor. Here, we watched a relatively fresh male careering around in search of a female, but with no other individuals of either sex present over the previous day or two, he suddenly climbed high and headed south at 12.30 pm. By the time I reached Lancing Ring, Lindsay had already searched most areas. We ended up with a total of seven, three of which were in his garden.

Over the next four days we worked together, looking for Long-tailed Blues in every nook and cranny of the site, finding them over c.0.75 km. Our combined totals of 10, 12, 20 and 22 on 5th, 6th, 7th and 8th October recorded the build towards peak abundance, as the situation looked very different when Paul Atkin and I visited on the afternoon of 9th October; we managed to find just three, following a mass exodus.

[Neil Hulme]

10 October - 5 November 2023

The 2023 Long-tailed Blue season started to gradually wane over this period, with counts generally being in single figures from sites including Lancing Ring, Seaford and Eastbourne (several seafront locations).

My last really fruitful day with this species occurred on 22 October at Pagham beach, where I saw 11 individuals under warm, sunny and windless conditions. I made the most of this visit, as the weather was forecast to deteriorate; it certainly did that - we were on the very cusp of a depressingly dull, wet and windy late autumn and winter.

After searching through mainly well-worn butterflies for an hour or two, I finally came across a little gem - a mint condition male which had probably emerged earlier that morning. One of the locals came out of her beachfront bungalow to see what I was photographing. Having explained the life-cycle and amazing journeys these tiny butterflies undertake, we watched as he sped out across the pebbles towards the sea.

As I walked back to the car, I was sure that this was the end of the fun for another year, and so it proved to be. Dwindling numbers of battered males continued to be seen by others along the coastal strip, until a last stand was made in Lindsay Morris's garden on 5 November.

[Neil Hulme]

Winter 2023/2024 Work Parties - BC Park Corner Heath & Rowland Wood

Every spring and summer, large numbers of people visit these reserves in Sussex, to enjoy the lovely butterflies, fantastic reptiles and wonderful flora. However, other than those directly involved, I doubt that most people appreciate the efforts that go into maintaining and constantly improving the wide variety of habitats here.

The volunteers that turn out, week after week, come rain or shine (mainly torrential rain this winter), never fail to impress me. This year, following some epic fails on the part of commercial contractors, they have gone above and beyond what you might expect volunteers to tackle; more than 40 tonnes of timber have been cut-up and shifted by hand, and more than 3 km of rides have been managed by brushcutter. There has also been much done in the way of scrub and Bracken management over open spaces, coppicing and wildlife corridor creation.

On Sunday 3 March, we celebrated the last conservation work party of the autumn/winter with a glass of wine. The reserves are in fine shape ahead of the 2024 butterfly season, so it's now just a case of sitting back and enjoying the fruits of our labours. When visiting this year, if you recognise any of the faces in the images below (which show only just over half of the events), please do remember to thank them - heroes, every one one of them!

All images by Paul Day.

[David M]

God knows, it's difficult enough to spend hours grafting outdoors at the best of times, so given the persistent wet conditions this last winter, these people deserve enormous recognition.

Respect.

[Neil Hulme]

Waxwings

By mid-January, and with all the fun of Christmas, New Year and Wassail now over, I was getting thoroughly fed-up, as I'm sure many other butterfly enthusiasts and lovers-of-summer were. Following weeks of wet and windy weather, the clear blue skies and strong sunshine on 19 January provided an unmissable opportunity to get outside. Deciding what to do wasn't difficult, as Waxwings had been reported in better numbers than for many years, including a decent sized flock on the outskirts of Hassocks. After about four hours in their company, I went home feeling considerably better.