THE PURPLE HAIRSTREAK MOVES EN MASSE INTO THE BRADFORD METROPOLITAN DISTRICT OF THE WEST YORKSHIRE PENNINES

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"Once upon a time I, Chung Tzu, dreamt I was a butterfly, fluttering hither and thither, to all intents and purposes a butterfly. I was conscious only of following my fancies as a butterfly and was unconscious of my individuality as a man. Suddenly, I awaked, and there I lay, myself again. Now I do not know whether I was then a man dreaming I was a butterfly, or whether I am now a butterfly dreaming I am a man".

                                                                               Chung Tzu. 4th Century BC.

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    There was an unexpected and welcome consequence to many a long summer's day scanning the tops of oaks in West Yorks and especially in the Bradford Metropolitan District. On falling asleep the mind's eye became filled with lingering images of oak trees. And if suddenly awakened through the night, the oaks would still be there as if indelibly stamped upon the retina.

     It was an intensely therapeutic experience because it overwhelmed the care worn thoughts that creep upon a person when alone in bed. This story without a narrative, told of countless hours passed transfixed before oaks as if in a trance or mad, looking for that tell tale silver flash denoting a Purple Hairstreak high in the branches. Passers by would give you a wide berth and even dogs were wary.

    There was an almost subjective aspect to this experience of looking for Purple Hairstreaks. Their appearance, if you like, could be willed because to see them required a steadfastness of purpose. Permitting the mind to wander for even a few seconds and all would be lost. We had become what we were looking for.

    There were days when I could not muster that power of concentration and then the prizes would go to my brother. The study of Lepidoptera in the field is notorious for its superstitions and rituals. Success is dependent upon there being some fine weather for at best a four week period during which time the insect can hopefully be seen. For some butterflies, like the Black Hairstreak, it is only a matter of days. But the experience of looking for the Purple Hairstreak was different from the wish-fulfilment of dreams. It was also a cognitive process and as the days passed, with each successive sightings, our eyes grew sharper. With a gathering sense of wonderment, by late August 2001, it was becoming clear the Purple Hairstreak had penetrated into, and most probably through the Pennines, all but unseen.

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    Undoubtedly, the Purple Hairstreak is nowadays by far the most common Hairstreak in the hills, valleys, carrs and royds of West Yorkshire. Yet a cursory glance of their typical haunts - the many oak trees, copses and woods that mark the area - you could be forgiven for thinking they scarcely exist except in a handful of localities and then in very small numbers. The warm spring of 1997 was decisive in the number of Green Hairstreaks recorded and the discovery of new colonies. But come the high summer some two and a half months later the same could not be said of the Purple Hairstreak. It remained all but absent from the official records. In truth, however, the Green Hairstreak was a laggard in comparison to the Purple Hairstreak which, "unfelt, unheard, unseen" had overrun vast areas of West Yorkshire in particular the Bradford Metropolitan District.

    The lepidopterist, Roy Bedford from Wakefield is right when he said the Purple Hairstreak is, "a much under-recorded butterfly in Yorkshire" but from our experience, we would maintain that it is much easier to see in some parts of Yorkshire than in others. Like, for example, on the Plain of York or in East Yorks. But even here it does not compare to the ease with which it can be found in parts of southern England. In fact, to shake a youngish oak in favoured spots can stir up a veritable silver shower of Hairstreaks at the height of the butterfly's flight period. Indeed they can almost become an irritant, sufficient to momentarily distract a person looking for Purple Emperors in the high canopy.

   To locate the butterfly a few handy tips are in order. Hard as it may seem look without preconceptions because you are looking for something whose behaviour in the butterfly fauna of Britain, is unique. It is more like looking for a fly, so small and insignificant is the butterfly when set against the mighty bulk of the oak. Just let the eye rove over the canopy and try not to fix on one spot. On an average summer's day wait, wait and wait anything from five minutes to an hour and try not to give up in disgust. The chances are you will eventually glimpse a fluttering, silver grey hop, as the butterfly rises from one leaf to settle on another close by. Up to the summer of 2001, we had looked for the Purple Hairstreak through southern eyes. For instance, we had decided in the spring of 2000 that the oak groves and slopes of Shibden Head, Queensbury, looked very promising indeed. A quick visit in July of the same year had caused us to decisively pronounce they weren't there when, all the time, they were probably laughing at us from high up in the canopy. (We still don't know if they are here because of foot and mouth restrictions in 2001).

    In the following text we emphasise in several places, our view that the habits of the Purple Hairstreak in West Yorks differs from those in the south. Their most salient characteristic is the tendency to stick to the tree tops. Perhaps this liking for higher altitudes is a factor in the butterfly taking to higher ground, which, in the case of Baildon Moor is windswept and considerably cooler. Could this behaviour be a response to changed climatic conditions - an elastic response as it were - or are the butterflies now "hard-wired" to survive more in the canopy than their southern counterpart' In the unlikely event the latter should ever be proven, then it is possible the butterflies may have spread out from undetected colonies going back 100s of years and the determinants of their behaviour are more genetic than climatic.

   Significantly, in The Millenium Atlas Of Butterflies In Britain And Ireland, the Purple Hairstreak distribution map for the Pennines remains a blank. It is obvious the butterfly is far more widespread here than anyone would have dared dream was possible even in the year 2000. Over the next few years it is necessary to try and determine its exact range and limits - if any.

    Most of the following information is distilled from jottings made in the summer of 2001 in the Bradford Metropolitan District. All in all, we found 21 new Purple Hairstreak sites, some where they flew in great abundance. In the case of Odsal Woods (South Bradford golf course) we were merely confirming what was already known: in the previous year when Derek Parkinson, a Baildon Lepidopterist, noticed two Purple Hairstreaks flying among the semi-mature oaks on the fringes of the golf course. A year later, on a overcast though very muggy day on August 13th, 2001, we counted 70 Purple Hairstreaks in the same area which also included steep railway embankments and individual oaks in surrounding fields. We still don't know for sure what the count would be on a still, sunny day at the height of the season. One final important point: by the time we came to make our assessment of the butterfly in the Bradford area, numbers were in steep decline, especially in early September when they would be in serious decline.
 

Purple Hairstreak Purple Hairstreak
 Purple Hairstreak
These three photographs taken on

September 2nd 2001 are the same

battered, female Purple Hairstreak

dying in the cold, damp grass field

on the eastern approaches to Royds

Wood part of the Judy Woods

complex, Bradford 12.   


What follows is a day by day account of the extent of the butterfly's range which is anything but complete.

     In late July, 2001, one of us made a visit to Elland cemetery in Calderdale because we had been informed the previous year by a wandering naturalist in Cromwell Bottoms that two Purple Hairstreaks had been seen on a nearby railway bank side. Later we were told by Calderdale entomologists that the butterfly flew in the cemetery. This confirmed our reckoning as we thought we'd maybe caught a glimpse of the Purple Hairstreak near Hardcastle Crags (1992) and Ripponden (1997). Over the winter period of 2000/2001 we determined on settling the question of the butterfly's elusive presence in the Bradford Metropolitan District. We thought it likely the Purple Hairstreak had progressed from Calderdale through Shibden Park up to Shibden Head (Queensbury) and also from Brighouse to Judy Woods (Bradford 12) which, as the crow flies is merely four miles away.

    Sure enough the butterflies were on the wing in the cemetery but not in any great number. By the end of the day unusual characteristics were evident, different to those we had observed in the south. Up to 14.00 hours the butterflies would descend briefly from the tall trees to tarry awhile on the leaves of small, sometimes very immature oaks often only a couple of feet high. After that they tended to stay put in the tree canopy, their visits to the lower branches becoming ever more infrequent. This behaviour was in direct contrast to the populations on the North Downs of Surrey where on a warm day the butterfly can be found nectaring on bramble from 16.00 hours until well into the evening. Secondly, we were surprised to find the butterfly in Calderdale favouring a free standing sycamore some 30 feet away rather than a nearby ash which, in the south, is their preferred haunt in addition to oak. Descending to the Calder canal, it was a delight to find the Purple Hairstreak in good numbers all the way along the canal path from Elland to Brighouse. When disturbed by walkers, invariably the butterfly would fly up from the small oaks on the towpath then dip down - almost skimming the water - only to rise in a beautiful arching sweep high into the sycamore canopy on the other side of the canal. At least twice butterflies were disturbed whilst resting on the Himalayan Balsam. Whether they were actually nectaring on the flowers is still in doubt. Others would come down from the small oaks, linger a couple of seconds on the Balsam before clearing the water and shooting up to the tops of the sycamore .

A further visit to Elland and the Calder Canal. August 9th 2001

    We found no Purple Hairstreaks along the busy Halifax/Huddersfield main road though the steep, high bank side, on top of which is Elland cemetery, is massed with oaks. In fact, we have yet to find a Purple Hairstreak on a roadside oak. Perhaps the exhaust and dust from passing traffic turns the aphid honeydew - that essential nutrition for the Purple Hairstreak imago - into an unappetising, even toxic glue. Given what appears to be the Purple Hairstreaks reluctance to descend and nectar on flowers in the north, aphid honey dew is even more of an essential nutrient than in the south. This factor alone could well prevent roads bordered with oaks from acting as a corridor helping the Purple Hairstreak to spread. But once we had dropped some 20 or 30 feet below the road to the Calder Canal within a minute we were seeing Purple Hairstreaks. In all we counted some 10 butterflies high in the oak canopy (though sufficiently distant from the road which here followed the canal for quite some way). Even at 17:00 hours it was still a warm haven, far more so than the cliff face descending from Elland's high cemetery. Turning off to Sowerby Bridge again we disturbed a couple on the Himalayan Balsam. Is the connection merely incidental or something more profound' The evening clouded over at 18 00 hours but not before we had noted two more on the Halifax arm of the canal.

    A general observation arising from having closely watched Green and Black Hairstreaks over the preceding four months. Purple Hairstreaks do not keel over to one side to flatten their closed wings against the leaves as do the Black Hairstreak and especially, the Green Hairstreak. In fact, with a nervy walking gait they strut over the leaves and up and down young stems searching perhaps for aphid honeydew and even sap. From time to time they stop and rest awhile opening their wings in the sunshine before flitting to another leaf close by. It is this behaviour more than any other that betrays their presence to the practised eye.

Judy Woods below Buttershaw and Wibsey, Bradford 12. August 10th 2001.

    Two weeks earlier one of us had walked through this woodland containing a fair number of old oaks and a mass of smaller oaks, which had grown up in the last 100 years or so once grazing ceased. We had in the spring convinced ourselves Purple Hairstreaks had to be here. Disappointed, we thought in all likelihood there were no Purple Hairstreaks in Judy Woods. Finally, convinced we must be wrong, one of us (David) returned and on that evening of August 10th persistence was rewarded. He had been looking through southern eyes and though there was a cool north westerly blowing on an otherwise clear evening he discovered them unexpectedly on the eastern fringe of the woodland in an area known as Royds Wood. Shaded from the sun but also sheltered from the wind, there was that unmistakeable flash high up in the oak canopy occasioning another flash: the flash of recognition. There appeared to be crowds of them, 50 plus or so, in this narrowly confined Purple Hairstreak cornucopia. Two descended from the heights whirling around each other in a close quadrille just above the grass. Eureka and ecstasy! Things would never be the same for Bradford and the Purple Hairstreaks and we were sufficiently inspired to press on.

Odsal Woods and Brownroyds Hill above Chapel Green and Little Horton, Bradford 5. 13th August 2001

    And press on we did regardless of the weather. August the 12th had been a blustery rainy day so we decided to reconnoitre these two sites chiefly to assess the number of oaks. We had previously come to the conclusion that in all likelihood the Purple Hairstreak would favour the more established woodland whose eastern limit in the Bradford area was Judy Woods. Generally the oaks growing in Odsal Woods and along the fringes of south Bradford golf course were young in comparison to the number of ancient oaks dotting Judy Woods and the immediate vicinity. Apparently, acres of oaks had been felled to make way for the South Bradford golf course in the first decade of the 20th century but it also seems likely that previously, oaks had been deliberately planted to bind together the railway cutting on the Bradford/Halifax line that runs from Raw Nook to Odsal Top. Oaks have a root structure equal to their visible area and hence were also favoured by canal builders especially when they had to gouge giant furrows through hilly terrain.

   However, August the 13th dawned reasonably bright though windy. We made our way up Brownroyd Hill but after staring fixedly without success at a number of oaks we moved on to Odsal Woods/South Bradford golf course a mile or so away. By now the weather was closing in and the day promised to be every bit as bad as yesterday though it continued to be warm and muggy. Walking along the sheltered path skirting the golf course and, though by now overcast, we were delighted to spot a Purple Hairstreak and then another and another''. Many others followed. Hey! They really do flutter about in damp, gloomy conditions in the north. It appeared to us these specimens were the sentinels of a large, even vast colony. Yet again, even on this inhospitable day, we noticed how it was only on trees sheltered from the wind we caught a glimpse of the butterfly. (Later on we briefly visited the site on a good day and we were not surprised to find it everywhere: even on an unpromising exposed spoil heap crowned by a couple of stunted oaks high above the railway cutting and no distance from the M62 feeder road running by the Euroways industrial estate).

    As the weather had improved we decided to try our luck once more returning via Brownroyd Hill. At 18:40 in the evening we struck gold, seeing the butterfly right where the oaks gave out on what appeared to be the most unpromising bit of all. How long would one have to try before it was possible to photograph the insect with virtually all of Bradford as a backdrop? And how did the butterfly get there? Perhaps it provided us with a clue as to the length of time the butterfly has been a native to the Bradford Metropolitan District because Brown Royds is not in the direction of the prevailing winds which could, at some time, have lifted an insect from Odsal Woods. An easterly would have been necessary for that and these winds are rare enough.

Brackenhill Park. Great Horton. Bradford 7. August 14th 2001

    All the same we thought there must be a limit and Brownroyd Hill was it. We were still some days away from reaching the conclusion we now hold: that every oak tree in the Bradford Metropolitan District is worth inspecting.

    So imagine the surprise when visiting Brackenhill Park as we had done on thousands of times previously, almost as if in a dream, a Purple Hairstreak lazily flapped its way into a small stand of oaks like one of those cardboard cut outs of butterflies we animated as children by pulling on a wire lever. Virtually on our doorstep, how could we have overlooked it for so long! And to think of all the time we had spent looking here in the past for the White Letter Hairstreak amongst the suckers of young elm! And all we had to do was raise our eyes and look up to the oaks to see a Hairstreak that in our wildest dreams we never ever imagined could be there.

Bireley Hall Woods and Wibsey Park, Bradford 4 and 6. August 25th 2001

    Work interrupted research. Eleven days later our investigation began again in earnest. On the aforementioned rainy day on the August 12th we had noticed a fair number of oaks behind the Yorkshire Building Society headquarters on the ring road between Odsal and Bierley. We also found the occasional oak in Bowling Park but in the rest of Bradford's parks like Peel Park they appear to be absent (is Manningham an exception?) On this rain-drenched slog we noticed, through binoculars, Bierley Hall Woods in the distance where, it was clear, oaks abounded. On a much better day on the 25th of August, our expectations proved correct and within a fairly short space of time we saw 3 Purple Hairstreaks on the abundant tall oaks. As it was getting late in the year this small number gives little indication of the actual size of the colony. Moving to Odsal Wood passing underneath the M62 feeder we were only to see two of the creatures and getting closer we observed how dished they looked. We came to the conclusion most of the population must have perished in the preceding eleven days. ( Even so we were to see a couple in the same place on the 14th and 16th of September respectively). But we could not be dissuaded from continuing on to nearby Wibsey Park arguing that because the park was even higher and more exposed to the north westerlies there was a good chance of a late emergence. Our hunch was correct and though it was starting to become overcast we saw three still flying vigorously around the low oaks about 18.30 hours in the early evening. On some of the park information boards put up by the council, mention was made of how in the 70's part of the park had been allowed to run wild. Where previously the grass had been close shaven, various trees were planted among which were oaks. This early eco experiment had born fruit because it was on these young oaks we saw the Purple Hairstreaks. An Asian family doing a bit of gardening were attracted to our enthusiastic shouts and peering over the fence were thrilled to learn that their garden was probably host to this little butterfly.

Bull Grieve Wood, Clayton Quarries and Scholemoor Cemetery. Bradford 14. August 26th 2001

    Partly as a result of finding the butterfly unexpectedly in Brackenhill Park in Great Horton we decided to pay a visit to Bull Grieve Wood which dips into a gully behind Scholemoor through which a small stream flows. It was here we espied a Hedge Brown in the mid 90s and the warm, damp conditions sheltered from the winds on all sides are just perfect for the Ringlet which, however, has yet to arrive. It is also a good spot for fungi like Fly Agaric and Shaggy Ink Cap. This was more of a jump than a short step to the next adjacent strand of oaks. However, we thought it essential in order to verify if the butterfly was still in the process of colonising Bradford. We had provisionally come to the conclusion there was a  "Calderdale effect" sweeping up from Brighouse and Halifax. But were we right' Standing for quite a while above a mass of oaks which climb up the banks of this wooded dell it seemed we were right in our provisional theorising. Slowly we moved around to the western edge of the gully skirting the perimeter of the quarries where some stately high oaks grow some distance from each other and which stand slightly apart from the main body of this rift wood. In this much more exposed position quite quickly we saw three Purple Hairstreaks and our provisional theory began to look weaker. Managing to get some photographs of a bedraggled specimen we then descended down the warm gully slopes covered in oaks without, however, seeing one Hairstreak. We came to the conclusion this surely be the main body of the colony which had perished some days prior to our arrival. Clambering up the other side of the gully and out on to the top we managed to catch sight of two other Hairstreaks on an exposed oak close to the Scholemoor estate. Scholemoor cemetery, a hundred or so yards away, produced a last desultory sighting.

The Leeds/Liverpool canal from Shipley through to Apperly Bridge and the side of Calverley Wood. Bradford 17 and 10. August 27th 2001

    Were Purple Hairstreaks on the wing in significant numbers way over to the north west of Bradford' If they had spread from Caderdale (the aforementioned, "Calderdale effect") this would constitute a big jump. The butterfly had been occasionally seen in Heaton and Northcliffe Woods and at Hollin Hall and in the vicinity of Esholt. Surely there must be more? A short distance from Dockfield Junction and the factories and warehouses of Shipley, smallish oaks often are to be found here and there along the canal bank. In next to no time we found our first Purple Hairstreak and from here to Apperley Bridge we recorded about 22 stragglers. Walking a little way beyond Apperly Bridge we caught sight of a couple more: high in the canopy of Calverley Woods there was that unmistakeable flash as the rays of the early evening sun glanced off these butterflies wings.

    We began to ponder on the actual size of these populations. Seeing how they appear to be far more reluctant to come down to ground level than their southern counterparts maybe one could arrive at a rough average by counting the numbers on any one tree then counting the number of oaks over a given distance or area? A simple multiplication sum would provide a rough guess but it was beginning to look as if their actual numbers were not far short of favoured spots on the North Downs like Ashstead Forest. Again we expressed astonishment how such a dense population had escaped notice.

    Crucially, different behaviour prevents proper assessment. How on earth have they been so over-looked for so long? The more one becomes aware of the insect's range in Bradford the more astounding this oversight becomes. The fact that canals and railways have been vitally important in the spread of the Purple Hairstreak into the Pennines may explain some of their behavioural idiosyncrasy. The oaks on the canals for instance come right down to the water's edge and the woodland floor is typically barren of all flowering plants including bramble. Consequently, they often have to fly across the canal before encountering any flowers. This may lead to a certain reluctance causing Hairstreaks to remain within the confines of the oak trees on the opposite side of the canal. This pattern of behaviour or something similar may not pertain to railway embankments. Despite difficulties of access, their behaviour in these spots needs to be observed more precisely.

The Leeds/Liverpool canal From Shipley to Hirst Lock through Hirst Wood to the aqueduct then back along the River Aire to Trench Meadows and up the bridleway to the top of Shipley Glen adjacent to The Old Glen House pub. Bradford 17. August 28th 2001

     We had barely passed Salts Mill before we encountered our first oaks around 14. 00 hours. There was nothing doing here. Moving on to Hirst Wood locks we saw our first Purple Hairstreaks on very tall oaks which fringe a small car park a short distance from the canal lock. We also detected the familiar flash on big, broader oaks bordering the railway side. Returning to the locks we also caught a glimpse of them on the smaller oaks nearby. As we walked along the canal toward Bingley we saw another 10 butterflies or so where Hirst Wood comes down to the edge of the water. The sun's rays, now becoming lower in the sky, were beginning to catch the oaks and on a late July evening it must be quite a sight as Purple Hairstreaks cascade down the trees on the far side of the canal embankment. Crossing the aqueduct we walked back towards Shipley via the banks of the river Aire stopping every now and then to give an oak the once over. Leaving the path shortly before Saltaire, attracted by a lone oak with its now inevitable companion - a Purple Hairstreak - we stumbled on Trench Meadows, the triple SSSI site resplendent with a huge, thick carpet of devil's bit scabious. It must be greater in length and breadth than Little Scrubbs Meadow, in Chambers Farm Wood, Lincolnshire, where the Marsh Fritillary flies. Whatever would English Nature think of a controlled introduction on what looks to be a perfect site? Today though the attention was on the free standing oaks in the meadow. It was a full 15 minutes before we caught our first glimpse of the Purple Hairstreak. But it was on the wooded slope of Trench Wood descending from the top of Shipley Glen that the butterfly was most active. Then something out of the ordinary happened, at least for the northern Purple Hairstreak. We accidentally disturbed one nectaring on devil's bit scabious! Purple butterfly on purple flower! What a missed opportunity for a photograph as invariably they are photographed nectaring on bramble flowers. But this was no freak accident because in the space of 15 minutes we saw two other Purple Hairstreaks flying low over the scabious. Having descended from Trench Wood they flew toward the oaks on the far side toward the Aire. This was around 16 30 hours and the time of day may turn out to be significant so it is well worthwhile taking a closer look in 2002.

    Walking up the bridleway to the top of Shipley Glen which comes out at the Glen House pub we looked amongst the tall oaks breaking the skyline oaks at the summit of Trench Wood. In spite of the wind and the exposure of the oaks to north westerlies we were in luck espying 3 Purple Hairstreaks in quick succession. All in all, we'd seen about 13 in the Trench Wood area.

   After these latest finds it was obvious the Purple Hairstreak really had taken complete possession of Bradford City which has undoubtedly now put itself top of the league table of urban sites for at least two Hairstreaks. What remained now was to determine the limit of the Purple Hairstreak's range which meant going further afield and ascending even higher ground. On the bus journey from Lucy Hall to Baildon we passed several fields dotted with ancient oaks which gave out just below Windy Hill on Baildon Moor. We resolved on taking another look.

Undercliffe Cemetery, Baildon Moor, Saltaire Road and the Prince of Wales Park, Eldwick, Bingley South Bog. Bradford 16 and 17. August 29th 2001

    So on the very next day we set out, aware that time had all but run out. But first a quick dash to Undercliffe cemetery where we caught sight of one lone Hairstreak. Then on to the approaches to Baildon Moor via Shipley Glen Road which runs from Baildon Moor to Lucy Hall. We each positioned ourselves before large oaks and gazed into the branches. Within minutes we had caught sight of one, and on every subsequent oak we cared to spend time looking at, we saw the same familiar flash. We were so impressed by this discovery we took a panoramic photograph of the area revolving through nigh on 180 degrees. Pressed for time, we had only had moments to visit a fraction of the oaks spread out below us. But it's a fair bet each oak contains a small colony. Interestingly, very few of the oaks we looked at on this slope had any fresh green leaves. In all they looked very autumnal and the leaves were beginning to turn yellow around the edges and yet still the butterflies continued to fly.

    We then walked up and up to the tree line and were rewarded to our complete astonishment with several Purple Hairstreak sightings above the caravan site of Crooked Park. Surely this must be the highest colony, bar none, of Purple Hairstreaks in this country. Not every day does a Lepidopterist make such a discovery and we were walking on air. It seemed to open a new chapter in the history of the butterfly in the UK. However, on climbing a little farther up to some exposed oaks just beneath the summit of Windy Hill we were disappointed not to crown our coup. But at the height of the butterfly's emergence it may well be worthwhile to take a second look. This really would be the insect's ultimate triumph because moorland birds were flocking in the trees and the chances of escaping predation by these insectivorous birds would be much reduced. Yet even if the butterfly is absent from these wind-raked trees, immediately below on the Crooked Farm caravan site there is undoubtedly a colony on the gnarled and twisted oaks of an indeterminate age. For all we know they may be like the oaks in Wistman's Wood on Dartmoor and be of a considerable age, their growth stunted by exposure.

     Descending from the moor toward Eldwick we saw a number of Hairstreaks in the oaks across the stream running alongside Saltaire Road. Arriving at the Prince of Wales Park we immediately made for the heather-clad upper reaches where thickets of splayed oak were growing and where, earlier in the year, the Green Hairstreak flies. Within 25 minutes between 16.30 and 17.00 hours we had spotted 3 Purple Hairstreaks, one flying directly over our heads a mere 8 feet from the ground. Descending the steep bank side of this intriguing park which somewhat resembles a 19th century Spanish park with its pines and more characteristically English beeches and oaks we espied another butterfly high amongst the exceptionally tall oaks. This steep slope, which catches the sun all day, may be the colony's core. It would, however, be difficult to verify because there is no vantage point from which to view the bank side at close quarters. As a finale, we walked along the canal from Bingley to Shipley noting a couple of Hairstreaks in the vicinity of Bingley South Bog and four at Dowley Gap locks. We could do no wrong.

Baildon Baildon
The covering of bracken surrounding the summit of windy Hill, Baildon Moor. Purple Hairstreaks have colonised the line of stunted oaks just visible in the middle ground.
Looking down from Baildon Moor towards Lucy Hall. Each individual oak most likely contains a small colony of Purple Hairstreaks.
 Elland  Opposite: Elland Cemetery, West Yorks

 around 1400 hours, August 9th 2001.

 Female Purple Hairstreak on low lying

 oak branches.


Skipton. September 1st 2001

    Three days later and our luck ran out as, incidentally, did the oaks. Between Steeton and Silsden and Skipton the number of oaks declines dramatically. As the railway and canal run across flat ground there was no need to plant oaks to bind bank sides together to prevent slippage and soil creep. The door at the end of the corridor had been slammed shut. It took at least an hour to locate suitable oaks in Skipton but foot and mouth restrictions kept us out of the grounds of Skipton Castle Woods. The day had also began to cloud in and we spent a fruitless couple of hours in a likely looking abandoned 18th century graveyard on the Grassington Road. On the fringes of the limestone upland the oaks that were present in Skipton had probably been planted deliberately. Typically, in the countryside around Skipton oaks are replaced by ash, crowned, as one goes further up Wharfedale, by the magnificent limestone ash wood of Grass Wood in Grassington. For this reason looking for the Purple Hairstreak here could be like looking for a needle in a haystack.

Return to Judy Woods. Bradford 12. September 2nd 2001

    On this dismal, autumnal day with occasional bursts of watery sunshine we set off, more in hope of turning up that elusive Speckled Wood colony which we thought may well be in Judy Woods. The medium format Mamiya camera had been left behind. What was the point of lugging that weight around? What an oversight because in the late afternoon walking by the side of the woods where we had first seen Purple Hairstreaks we noticed one on the lower branches of the oak some five feet from the ground. Fluttering weakly it almost fell on to the damp cold grass in the field. Once there it was unable to muster the strength to fly up once more and when disturbed it dropped ever deeper into the grass with a falling motion reminiscent of a Green Hairstreak trying to escape detection. After a while from the bottom of the grass stalk it mustered a painfully slow climb towards whatever heat and light there was to be gathered from the rays of the sun. We were witnessing the death throes of a Purple Hairstreak. When finally it opened its wings it was obviously a very dished specimen. For the majority of Purple Hairstreaks on this easterly fringe of the woods, this large field was their death bed and graveyard. In the Pennines, Icarus-like, the Purple Hairstreak spends its life in the top canopy of oaks, soaking up the sun, only eventually to fall to earth, never to arise. These aspects of the Hairstreaks behaviour need to be closely studied. A little later, in a hollow deep in the woodland, another Purple Hairstreak vainly flapped its wings as it sought to rise once more into the oaks. Giving up, it sank behind the bank of a stream becoming lost to view. We even searched the stream in the hope of finding its lifeless corpse. Early evening - and of a sudden - the sun shone brightly. Scanning a cluster of oaks we suddenly noticed a most agile Hairstreak possessing sufficient strength to fly into the brisk wind. Obviously, a few were more than just clinging on.

Keighley, Steeton and Silsden, Bradford 20 & 21. 3rd September 2001.

     There are certainly far more oaks in Keighley parks than in Bradford. For instance in Victoria Park in the Lawkholme district there are two reasonably sized oaks. In Cliffe Castle Park there are far more, all of sufficient size to each support a small colony though tending to stand apart from one another. Late, late, late, though it was in the season we saw one survivor. It seems likely they are present in considerable numbers in and around Keighley wherever oaks are to be found - e.g. Devonshire Park and the adjacent Alder Carr Wood fringing Keighley golf course where brief glimpses gave the game away. Again though, the very moment we arrived at the Leeds/Liverpool canal, poking our heads over a stone wall, we saw a Purple Hairstreak. Three more were seen that day right up to the dog's leg where the oak trees give out on the approach to Silsden on the canal bank side. And then - no more!

Some provisional general conclusions.  

  •     How long has the Purple Hairstreak been present in massive numbers in the uplands and valleys of West Yorkshire' In all probability not that many years. There is no mention of it in past records of naturalist societies. W E Collinson's book, The Lepidoptera of the Halifax Area, in the 1950s, omits the butterfly from his local lists whilst recording sightings of the Silver Washed Fritillary. It is possible the butterfly was present in small colonies in ancient woodland during the paleo-industrial era. Like so many other insects, the Purple Hairstreak has benefited from reduced carbon and sulphur emissions.
  •     Which leads on to our second point. Nowhere have we found evidence of the butterfly haunting oaks on roadside verges - even those on minor trunk roads. However, it is known to reside in roadside oaks east of Harrogate. Other Lepidopterists though have noted the butterfly's sensitivity to chemical pollution. However, the lone oaks in suburban gardens along West Lane/Lucy Hall Drive running from Baildon to Shipley Glen may contain a few. We are now convinced that its passage through the Pennines was almost wholly dependent on the railways and canals - especially the latter. It would, however, be worthwhile to slowly traverse the length of the Bradford to Manchester railway line via Todmorden, Littleborough, Moston and right into Manchester. It is true the oaks thin out after Todmorden but not enough to halt the Purple Hairstreaks expansion. The oaks that can be seen west of Littleborough tunnel tend to be immature and probably have grown up since the replacement of steam train by diesel. Notoriously bank sides would frequently ignite during the era of the steam train burning recently germinated oaks. (Railways, which ran through the fens, had the opposite effect burning off the reed smothering the delicate milk parsley, the Swallowtails food plant). Interestingly, travelling from Manchester to Wilmslow only resulted in the sighting of one Purple Hairstreak in the mighty oaks in Styal Country Park even though it was a perfect day for them. But how far does the butterfly extend in a north westerly direction towards the three Yorkshire peaks? Can the Purple Hairstreak be found in Skipton, Gargrave and beyond up to Settle and upper Cravendale? Or are we awaiting its immanent arrival? Perhaps it has leapt the remaining few miles to the Lancashire coast where the butterfly resides in considerable number on Gait Barrows? But more research is needed - difficult, arduous, but exciting research.
  •     Although the industrial revolution was probably primarily responsible for the virtual demise of the Purple Hairstreak in the Pennines, the hand that took away also finally gave back in an unexpected way. The original canal engineers were probably keenly aware that the oak had roots which spread as far, wide and as deep as does the branch structure above the earth's surface. As a binding structure containing soil creep it was unbeatable. A few decades later, the railway engineers adopted the same policy. There was one draw back though. Oaks take a long time to mature and their growth is slow so such a solution was also a long term one. Some 150 years later, together with the near demise of smoke-stack industry, railways and canals have become the major factors in the spread of the Purple Hairstreak. Recent global warming must also have helped. Porritt, for instance, originally noted the creature in the Doncaster area. Little could he have realised that the oaks recently planted along the rail network fanning out of Doncaster would help spread the butterfly to many an outlying Yorkshire region.
  •     At the same time young oaks were being planted along railway and canal banks they were being felled in far greater numbers for machine frames before wood was replaced with wrought iron. More generally the wooded sides of magnificent hills and mountains were denuded of timber to be used as fuel in the iron smelting furnaces of Sheffield and places like Low Moor in Bradford. The bare-backed Pennine hillsides came into existence as a social not a natural fact. There were also ideological factors to the planting of oaks. The canal network was well under way when Nelson defeated Napoleon in his oak ships at the battle of Trafalgar in 1805. And the opening of the first steam railway was only 20 years away. So planting oaks was a patriotic duty as well as serving a functional purpose on railway and canal embankment. But once the first wrought iron ships were built in the 1870s,"Hearts of Oak" sentiment was reflected in the merely ornamental planting of oaks in the parks and suburban gardens of the industrial and colonial middle classes. Of course, there was also a natural spread of oaks assisted by squirrels and jays etc which eventually would lead to entire bank sides becoming covered in oaks once protected from felling. There is a particularly outstanding example of this process on the fringes of Royd Wood, part of the Judy Woods complex. On open grassland (on which there had been a market garden some 100 years previously) young oaks have spread some 70 metres either side of a large oak. It is unlikely the most violent storm could have carried acorns that far and the only other explanation is that squirrels had buried the fruits and then forgot to retrieve some of them.
  •      Would it be reasonable to expect to find the Purple Hairstreak away from its main corridors, the canals and railways? Obviously, this does not apply to the Plain of York and it seems scarcely credible that only five years ago we recall reading in The Argus that every oak their was worth investigating causing us to bemoan its absence in West Yorks! Also, we are in need of a detailed search of the North Yorks Moors and the more northerly Pennine dales. The butterfly has been recorded in Nidderdale, Wensleydale, Swaledale etc but was this on the valley floor or high up the valley sides? The Baildon Moor colony shows the butterfly is capable of surviving at high altitudes and well able to weather the storms and winds. But is this necessarily true of the slopes of Pendle Hill, Ingleborough or Pen-Y-Ghent?
  •     And why is the butterfly all but absent in Wharfedale? Is it only a matter of time before it arrives? Standing on top of the north east quarried face of Baildon Moor it is easily possible to trace stand after stand of oaks going all the way from the Leeds/Liverpool canal near Esholt around into Wharfedale. Plantation Wood to the east of Otley is resplendent with likely oaks but no Purple Hairstreaks fly here it seems. Hours spent crawling around the railway bank sides and dodging trains across the field from Ben Rhydding gravel pits and not a sniff. The final humiliation came when standing in a field contemplating a free standing oak, a farmer approached to say although it was a public footpath there was a rampaging bull loose so, in the interests of safety, we must leave. How very Wharfedale to try by foul means or fair to limit the right of access! It is one of the few places in the north of England where naturalists straying off the beaten track are looked on as animals. Above Addingham on the Silsden road to Keighley in Airedale large oaks abound. These disappear on the exposed watershed that marks the boundary between Wharfedale and Airedale then reappear as the road descends into Silsden and Keighley. This is a possible transmission belt and it would be a turn up for the natural history books if the Purple Hairstreaks were present on these oaks but not on those, more ideally suited oaks, in Otley. A little later one of us spoke to the Lepidopterist David Howson who resides in Ben Rhydding. He, with others, had done a thorough search of that part of Wharfedale but had come up with next to nothing apart from seeing two Purple Hairstreaks in Middleton Woods lying to the north of Ilkley across the Wharfe. Middleton Woods is an ancient woodland containing large oaks and it is surprising just a couple were seen. Interestingly, a little further down the Wharfe close by the Harewood Estate yielded nothing after an admittedly brief search. If Purple Hairstreaks are in lower Wharfedale where do they begin? Presumably they must have moved westwards from the Plain of York.
  •      Is there a more than incidental relationship between the Purple Hairstreak and the Himalyan Balsam? We have only ever seen them at rest on the flowers by the side of the Calder Canal around Elland but it was on two occasions separated by a couple of weeks. It seems unlikely they would be nectaring because the bell-shaped flower would prohibit the butterfly from entering and its proboscis is too small to extract the nectar without so doing. So far either, we haven't noticed Hairstreaks descend for an evening sup on bramble flowers in West Yorks. However, we have never seen Hairstreaks feeding on devil's bit scabious before as they did in Trench Meadows. It is possible the habits of the Purple Hairstreak change as they age preferring flowers for an hour a day following the emergence from their ground pupation lair. After that they may prefer the oak leaf aphid sweet meats in the canopy. Or does this only really apply to the Pennine region? Moreover, between imago youth and old age low altitudes are given generally a miss when it again descends through weariness to earth. If we saw battered singletons on grass in early September, why shouldn't we see them on the heather in the Prince of Wales Park in Eldwick, Bradford 17?
  •      One can only marvel at how the Purple Hairstreak has succeeded in conquering the cities and countryside of West Yorks on territory that was formerly so alien to it. The dramatic suddenness of milder winters beginning some 10 years ago and the easing of carbon and sulphur emissions from smoke-stack industries and trains can never be sufficiently emphasised. But there must be another factor also. It is possible that more insects reach the imago stage from a single clutch of eggs than is usually the case when populations were not in flux. Darwin always maintained the balance of nature ensured that of the parental offspring only two would reach adulthood. However, the equation is upset once a species is able to exploit a new niche as the Purple Hairstreaks are doing in West Yorkshire. It could be the insect has outrun for the moment its predators, particularly parasitic wasps. For some reason the latter may prefer the lower branches of oak trees and given that the butterfly shows a definite preference for the high canopy, egg laying may tend to take place here also.The name Purple Hairstreak refers to the bands of purple on the upper sides of the male and female. It appears to serve no other function than sexual display. Otherwise the dominant impression in the field is of a blue gray, slightly buff, silvery colour as the underside wings are invariably turned towards the spectator - and the butterfly's predators. It is an apt combination for the oak, particularly when the insect perambulates up and down the young shoots of oak. The colour almost perfectly matches the young twigs which are encased in a kind of transparent cling film (which may be a defense mechanism guarding the tender shoots against insect attack) that turns a bluish colour when wrapped around the brown twigs. Also oaks, particularly in wetter areas, may often suffer from oak mildew fungus which in its early stages mottles the leaves with grayish brown patches of hyphae produced by the fungus spores and resembling the underside of the Purple Hairstreak. If stationary on one of these leaves that show signs of being attacked, the butterfly is easily overlooked. During the later stages of the disease, the trees appear covered with a fine, off-white powder - a not unfamiliar sight in West Yorkshire. Once this happens the butterfly seems to forsake the tree for good.



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       Having spent countless days looking up at the oak canopy we observed another cryptic phenomena. On most days on West Yorkshire's high ground a wind shakes the trees. Rather than the entire tree branches and foliage bending to the wind in one direction only, springing back once the gust has abated, different planes appear to move against each other, so one gets a very definite sense of front, intermediate and back plane. They are "tossed" by the wind and this conventional description can hardly be bettered. If the sky is clear or broken by clouds, chinks of blue will briefly appear like the flashing of a heliograph amongst the leaves, to be followed by another in quick succession, which to the lazy eye can be mistaken for the jinking flight of the Purple Hairstreak! Yet it may save many a Purple Hairstreak's life and given the fondness of the northern Purple Hairstreak for the high life, could well be a factor in the insect's successful colonisation of the region. Mistaken perceptions are central to the survival of butterflies. For purposes of concealment it is mostly on the underside of butterflies wings that deceit is stamped. However, study of the upper sides of butterflies wings has, other than their eyespots and pronounced bands, been much neglected.The draught board markings of Fritillaries, Chequer Spots etc may have an equivalent role to play in flight. A waving field of grass tends to blur into a grid of moving lines and almost angular shapes ceasing to resemble individual grass stalks. (This can best be seen on soft focus film or video footage and could be profitably investigated scientifically ). For example, against this moving background a Heath Fritillary in flight can lose itself with ease.

A final word. It is a pity not more Purple Hairstreaks cannot be found with relative ease in Bradford's parks. This is due to the paucity of oaks. An oak tree planting programme would eventually bring them into the more intensely urban areas of Bradford.

                                                                              David and Stuart Wise. Winter 2002.

There are to be sure many more points to be made. The really pleasant thing is the on-goingness where one is able to add, to modify or change completely, previously existing views if experience and theory demands it. Taking photographs in the Bradford Metropolitan District will not be easy. To take them in situ with, as a background, a panoramic view of Bradford would be a real achievement. If what we say about their behaviour is right, low level shots will be a betrayal of their true "local" identity and we have not the wings to record their behaviour more accurately!

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A later addition........

(The following is an extract from a letter to Sam Ellis, summer 2003, published in "Street One & Codlings" elsewhere on this web).

  "I was also interested to read about the discovery of the Purple Hairstreak in Durham City. Two years ago we found it all over the Bradford area even up to where the stunted oaks gave out close to the summit of Baildon Moor. Encouraged to venture further afield last year we found it in Skipton Castle Woods. These specimens were still in pristine condition unlike the dished examples we were seeing around Bradford at the same time and which suggested a later emergence. This year we intend journeying to settle and beyond to Dent head in the hope of finding in the high Pennines.

      I am also beginning to wonder if the Skipton colony, in particular, is not an ancient colony which may have been there since time immemorial but which has escaped notice because of the Purple Hairstreaks secretive habits in these northerly latitudes and relatively high altitudes. Their behaviour is so very different to their southern counterparts and it took us some considerable time to learn how to look for them. Only rarely do they descend from the oak canopy and the best time to get a closer look at them is toward the end of their brief lives when they literally seem to fall to earth in a crazy, almost uncontrolled fashion. To say that they are on their last legs is not just a manner of speaking because the northern Purple Hairstreaks do appear to spend far more time perambulating around the twigs and branches of oak trees, interrupted by the occasional brief flight. I even speculated if the Skipton butterflies were in the process of becoming flightless, virtual butterflies! "