LTBs in Southern England

[jasonbirder]

As I started Butterflying too late to catch the 2013 LTB influx...I'm still hoping to catch up with one!
Looks like there are a few about on the South Coast...
I've a work appointment in Chichester tomorrow....finishing about Lunchtime...so if any public spirited UKB'er wanted to PM me with any info it would be gratefully received....
Otherwise I'll probably swing by and have a look at Kingsdown Lea's just on the off-chance...
Thanks in advance!

[bugboy]

I was going to start a very similar thread but since Jasonbirder got here first I'll just piggyback on this one. Just watched the Countryfile weather forecast and looks like this fine weather is hear for at least another week. I'm off on Wednesday and next weekend so assuming they haven't all emerged and buggered off by then (or netted, killed and pinned ) I would like to try my luck at catching a glimpse of one too. Any info on sites reasonably near public transport stops would be greatly recieved

Thanks in advance

[Neil Hulme]

Hi Jason and bugboy,

The British emergence of LTBs is underway, but they are still few and far between and require a LOT of searching out. However, numbers should increase markedly once we get into the second week of October, giving a much better chance of success.

This is because the influx of primary immigrants stalled badly in August, due to inclement weather. At the time, I thought that the event had fizzled out. The progeny of those earlier arrivals are the adults on the wing now/imminently.

However, the mainstay arrived once the weather picked up at the start of September, and the majority of eggs went down during the first and second week of the month. I know this from looking at ratios of hatched/unhatched ova.

All of this suggests to me that we should see numbers increase significantly around 10th October, given the average timing of the complete life cycle, based on the literature and captive breeding studies by Mark Colvin. The emergence may continue until the third week of the month, unless curtailed by cold weather.

Between now and about 10th October I imagine we will see a slow build in sightings, but it’s still a little early to pick out where hotspots are likely to develop. Potentially anywhere that a large amount of Broad-leaved Everlasting Pea grows will produce the goods.

Of the British brood in Sussex, two have been seen in/near Hotham Park (Bognor), two ‘definites’ and several ‘probables’ have been seen at Newhaven Tide Mills, and on Saturday I watched one through binoculars behind railway security fencing at Lancing (sadly out of reach).

The best is yet to come, but although there may still be fresh specimens emerging, expect sites to empty out quickly around mid October. I suspect that all females and some males head south. In 2013 I saw a population of at least 7 adults, all of which seemed to have plenty of life in them, vanish within 48 hours, with the last LTB seen flying high and fast in a southerly direction over a steep road embankment.

BWs, Neil

[bugboy]

Thank you for the info Neil

[peterc]

A lot of useful information there, Neil. I am very tempted to go down to Sussex myself in the next week or so.

ATB

Peter

[Matsukaze]

Hi Neil,

Is the everlasting-pea the only foodplant used in Britain, or is it simply the most commonly available suitable plant? As I understand it, the butterfly will make use of many legume species across the world.

[Neil Hulme]

Hi Matsukaze,

I have no doubt that they are using a very wide range of plants other than BLEP, and I proved the use of Broom at Seaford in 2013. BLEP has become the main target for searches as it grows quite widely as a feral species and is easy to spot due to its tarty pink flowers. Hence I've spotted some great sites from the car and a speeding train!

Many of the cultivated species they are almost certainly using will be growing in private gardens and allotments, but it wouldn't be appropriate to encourage the searching of these areas. However, if you are an allotment holder near the coast, and have the right to roam, this would be a very good alternative to hanging around the stands of BLEP.

BWs, Neil

[Matsukaze]

Thanks Neil - I would guess that one requirement is a decent-sized seed pod.

[jasonbirder]

Thanks for the great info! Very helpful indeed!
Looks like I'll have another bite at the cherry over the next week or so...even though yesterday was unsuccessful!

[Jack Harrison]

I asked Neil a similar question having been unaware of this thread.

Next question: how far north along the Atlantic coast of France, Spain and Portugal is LT Blue resident if indeed is is resident along those coasts?
In other words, where might be England's nearest source of immigrants early in the season?

Jack

[Chris Jackson]

Hi Jack,
This is not a direct answer to your question.
The last time I saw an LTB in the area of Marseilles / Vitrolles (South of France) was in calendar week 41 (3 weeks ago).
Where they came from and where they have gone, I don't know.
Will I see some sort of return wave heading South ?
You will be the first to know. I check my scrub area at work most lunchbreaks.
Chris

[millerd]

From what I have read about the Long-tailed Blue, both here and in various books, they (like the Painted Lady) are pretty well a global butterfly but are only truly resident where the temperature remains sufficiently high for them to breed year round. In the summer, they move north, breeding after the frosts have finished. Dependent on favourable winds and weather, they then seem to end up on the continental coasts nearest the UK sometime in July/August. Numbers will vary from year to year (as with the Painted Lady) and if high enough, they will head that bit further north and appear on the south coast of the UK. With benign conditions they will breed until a trigger (day length?) sends them south again. Compared to the Painted Lady, LTB appears not to be capable of long migration flights in one go, but only in shorter "hops", meaning more generations and therefore their appearance here is later in the year.

To answer Jack's question, I would therefore expect the Mediterranean coast (perhaps also southern Spain and Portugal) to be the nearest spots where the LTB is truly resident.

2013 and 2015 have been particularly good years, but odd ones turn up in quite a few years. We are of course increasingly aware of the possibilities now and who knows what we have missed in other years without the incredible efforts of Neil and others to seek them out. With a warming climate (hopefully not offset too much by the North Atlantic Temperature Anomaly), these good years should become more frequent.

I have to say this is to an extent speculation on my part, building on assertions I've read. What do others think?

Dave

[Matsukaze]

I've seen Long-tailed Blues in the Malaga area in the first week of January, also in autumn and spring. Whether they are present during the summer as well I do not know; it might well be too desiccated for them then.

[Wolfson]

I see them near the coast in the Basque region of Spain from mid-July. I have never visited this area in June, but have not seen them on my brief visits in May. It is a long crossing from Bilbao to the UK so maybe the French coast is a more likely departure point. Attached photo taken near Bilboa on 24 July 2014.
Wolfson