In Pursuit of Butterflies

by Matthew Oates

  Spring was in danger of overheating. April slowed it down, just a little, producing a cold third week. Then, from St George's Day there was no holding it back, with the first Duke of Burgundies appearing at Noar Hill, along with a significant hatch of Dingy Skippers and Holly Blues. Diary: This has the makings of an excellent butterfly year… At the end of the month the Pearl-bordered Fritillaries began to emerge, down in the New Forest, and I even saw an absurdly early Small Blue at Noar Hill, where the Duke of Burgundy was having a bumper year.

  The spring of 1990 belonged to Harewood Forest, the ancient forest that straddles the A303 just east of Andover in north-west Hampshire. I had surveyed the insect fauna of the northern sector for the Nature Conservancy Council in 1989, and now had to investigate the southern third. Much of this southern block was old oak woodland, either high forest or derelict oak coppice with a heathy ground flora where the Clay-with-Flints cap had leached. Best of all was a shallow valley where the chalk came to the surface. I called it Happy Valley, for I was immensely happy there. Here, in an area where outgrown oak coppice had recently been thinned, was a magnificent colony of the Pearl-bordered Fritillary, visiting their beloved Bugle and Bluebell flowers and skimming low beneath the myriad yellow-greens of young oak leaves. The colours here – sapphire sky, yellow-green oak leaves, deep blue flowers, golden butterflies – formed the perfect combination that is forever spring. A Cuckoo called, perhaps eternally. A relic area of chalk grassland on the forest edge contained a few Dingy and Grizzled skippers, and several Duke of Burgundies, all tussling together. By May 25th the Pearl-bordereds were on the wane but a surprisingly large hatch of Duke of Burgundies had occurred: I counted 90 spread out along Happy Valley, fighting with each other and their arch enemy, the Dingy Skipper, launching themselves at passing Pearl-bordered Fritillaries and visiting Bugle flowers. True woodland Burgundies they were too, small and dark, breeding on Primrose, and flying much later in the spring than their downland counterparts. Holly Blues were present in high numbers too. Drought was kicking in, and many insects were seen imbibing the last of the moisture remaining along the woodland rides, including at the vestiges of the last puddle, two Burgundies, two Holly Blues, a Peacock, and a Pearl-bordered Fritillary. It was a time of kicking dust and cracks appearing in the rides, and Harewood revelled in it. Beneath the oak canopy Britain's dullest moth abounded, the aptly named Drab Looper, along with its foodplant, Wood Spurge.

  Noar Hill produced an exceptional emergence of its star butterfly, the Duke of Burgundy. Habitat and weather conditions were, for once, spot on. On Monday May 7th, under an azure haze, I counted 96 of them along the butterfly transect route, which takes just over an hour to walk. This remains a transect record, anywhere. I failed to attain the century because a lone butterfly photographer had ensconced himself in the Top Pit, the butterfly's favoured area up against the Beech hanger, and had displaced most of the resident males from there. Many butterfly photographers do not know how to move amongst butterflies without disturbing them. By the end of a perfect May the Dukes were almost finished for the year, having laid a remarkable number of eggs – by mid-June virtually every suitable Cowslip plant on the reserve was peppered with holes left by Burgundy larvae.

  In mid-May, Ivinghoe Beacon in the north Chilterns challenged Noar Hill for the right to be lauded as Britain's premier Duke of Burgundy locality. The way to sort this out was to conduct timed counts during the peak season period over the main flight areas of both sites, in good weather conditions – which for this butterfly means calm hazy sun. Luckily May 1990 produced many such days. At Noar Hill, 198 were counted in ideal weather on May 5th, and at Ivinghoe 207 in three hours of eye-straining concentration. Noar Hill won on a faster scoring rate (determined by cricket's Duckworth–Lewis method), averaging 1.32 individuals per minute as opposed to Ivinghoe's 1.18. It was a close-run thing.

  The Holly Blue was ubiquitous that spring, in town and country. Normally the spring brood lays its eggs almost exclusively on Holly buds, favouring female trees – for the larvae feed on and even in the developing berries. But in 1990 they were also laying eggs commonly on the flowers of Dogwood, which was strongly favoured at Noar Hill, Purging Buckthorn on the west Hampshire downs, Alder Buckthorn on damp heaths, and elsewhere on Privet and Spindle. A number of berry-bearing garden shrubs were also selected, notably Portuguese Laurel and Snowberry. Like the Burgundies, though, the brood was all but finished by the end of May.

  By then the season was so advanced that many spring butterflies were nearly over for the year, including Dingy Skipper, Duke of Burgundy, Glanville Fritillary, Pearl-bordered Fritillary and Orange-tip. Also, some of the summer species were remarkably advanced: summer-brood Small Tortoiseshells started to appear in Hampshire in late May, whilst in the woods White Admiral larvae were pupating. The downs had turned grey as drought conditions stealthily developed. The five months from January to May had been the warmest for at least 300 years. Then the weather broke, slowly and subtly, from June 1st. Gloom descended, accompanied by heavy showers or drizzle, giving day after day of lost time. The 1990 butterfly season stalled as, yet again, June proved to be a neurotic month.

  The hot weather returned with a vengeance on July 11th, but by then much damage had been done. The most obvious casualty was the Large Skipper, whose flight season coincided with six cool and cloudy weeks, but some other butterflies suffered from becoming trapped in the vulnerable pupal stage for too long. The White Admiral appeared in very low numbers, probably for this reason. Had the fine weather held it would have come out at the start of June, if not earlier, as I had found a near-full-grown larva in Harewood Forest on May 3rd. As it was, the first Hampshire individuals were seen on June 19th. Then, and perhaps equally significant, the butterflies that did emerge had to contend with much bad weather, including a tremendous gale on July 4th. The Purple Emperor suffered similarly. Ken Willmott, whose heart is eternally Purple, reckons it was the poorest Emperor season he had known. I struggled to see a pair, close by in Harewood Forest. First, a male flew low and slow past me, with scarcely a wingbeat, and glided off under the oak canopy in search of a sap run on which to feed; then the Empress herself appeared around a group of shady sallow trees, where she was going about her business. This was quality, not quantity.

  A week was spent surveying for High Brown Fritillaries on Exmoor, but little progress was made owing to poor weather. The weather allowed me one good day, during which I discovered a series of small colonies on south-facing Bracken slopes above the East Lyn River downstream of Robbers Bridge, in Lorna Doone country. Sadly, the butterfly was never recorded again in those rough paddocks. Also, a delightful little combe just north-west of Exford produced small colonies of High Brown Fritillary and Marsh Fritillary, as well as a lone Heath Fritillary, plus the more standard fare of Dark Green Fritillary and Small Pearl-bordered Fritillary – five species of fritillary. Within a decade the combe had been taken over for horsy culture and all its fritillary butterflies had gone.

  In early July the second brood of the Holly Blue began to emerge, seeking world domination. This azure butterfly was even more profuse than in the spring, and easily won Butterfly of the Year. The brood peaked at the turn of July and remained prominent until a wet and windy third week of August, which relieved the developing drought conditions. As is their habit, most summer-brood individuals were seen on or around flowering bramble patches, with females also visiting flowering Ivy growths on which to lay their eggs. Later, a scatter of rare third-brood specimens was seen during September and October.

  Two days of intense heat were spent up on the Morecambe Bay limestone hills with Martin Warren, looking closely at where High Brown Fritillaries were breeding, and also assessing the strength of Duke of Burgundy colonies by looking for the distinctive larval feeding marks on Primula leaves. We spent an oven-like day on Whitbarrow, north of the Kent estuary, where the High Brown was at peak season, and wonderfully numerous, and an even hotter day on Gait Barrows NNR down near
Silverdale. Here, the butterfly flies and finishes earlier in the season than on the high hills, and was starting to look tired and ragged. It was wet-hat weather – take a white sunhat, soak it in water and put it on your head, and top it up regularly. That stops the brain from frazzling, though it produces a sticky damp patch at the base of the neck. I learnt it from an Australian who captained me at cricket. Without a wet hat the intense heat off the grey limestone rocks on Gait Barrows would have generated hallucinations, or even dried up the blood. High Browns, of course, loved it, and were darting about frenetically, and all was well with the world. The Burgundy had already had a good time, judging by the abundance of Cowslips and Primrose leaves bearing the tell-tale eating marks. Up on Arnside Knott, the Scotch Argus was just beginning to emerge – we saw the first two males.

  The heat intensified. A massive anticyclone came over for the start of August, in time for a field-course weekend I was running on insect ecology at the newly opened Kingcombe Centre in west Dorset, just a few miles from my birthplace. It was to be a memorable weekend. The Kingcombe Centre came into being after one of the many celebrated conservation crises of the 1980s. In 1985 old Arthur Wallbridge died aged 94, blind and intestate, having farmed 600 acres of low-grade agricultural land in a west Dorset valley in the old-fashioned way. He avoided chemical sprays and fertilisers, and did not drain the marshy meadows. The outgrown hedges were managed by hand. Time stood still here, surrounded by a world of agricultural intensification and habitat loss. This was the Dorset Thomas Hardy knew and loved. After the National Trust failed to purchase the farm, Lower Kingcombe was acquired by a property developer for half a million pounds and split into fifteen lots for resale. The Dorset Wildlife Trust met the challenge of raising £150,000 in a month to purchase the SSSI meadows. The remainder was sold off in plots associated with rundown buildings, which were prime candidates for conversion to weekend homes for wealthy Londoners. The yuppification of the countryside was well under way.

  One such plot, a few acres of tumbledown and a couple of derelict barns, was purchased by a young biology teacher from Blandford Forum, Nigel Spring. A man of vision and immense energy, Spring tamed the jungle and rebuilt the barns as an environmental studies centre, which opened in 1988, offering short courses for adults and children. Spring and Oates first met at a Jimi Hendrix concert in 1970, and were destined to meet again. Over the years I ran a number of long-weekend butterfly events, the odd course on other insects, and contributed to a long-running course on managing grazing animals for conservation. But it all began on one of the hottest weekends in the history of the British Isles, when the temperature reached a staggering 37.1 degrees Celsius in Cheltenham and 37 degrees in Leicester. My course participants rebelled en masse, and threw themselves into the sea at Ringstead Bay, where we had gone to see Lulworth Skippers and other insects – all except for one who was wearing a wet hat, and a lady from Madras who was not in the least bothered. Earlier I had taken them to a bog on Purbeck where they had been eaten alive by a rare species of horse fly, Chrysops sepulcralis, a Purbeck speciality, and been treated to a good flight of Graylings and the last Silver-studded Blues of the year.

  August was heating up, and drought was returning. A visit to Alice Holt Forest on August 5th found Hazel leaves yellowing and curling, Honeysuckle leaves turning brown, the grasses in the rides droughting off, and deep cracks and fissures appearing in the clay. A second brood of the Small Pearl-bordered Fritillary was emerging. This occurred in central southern England only in the hottest of summers.

  A visit to Watlington Hill in the Chilterns on August 7th found the drought conditions badly compounded by heavy Rabbit grazing. Diary: Today the turf was ludicrously and dangerously short, sun-scorched and void of flowers. There's few things worse than a droughted Rabbit desert. The bunnies had even nibbled off the Ground Thistle buds and were starting on Hawthorn bark (which they strip during severe winter weather). Silver-spotted Skipper numbers were well down, probably in part owing to poor weather during June, though doubtless in the main because of excessive Rabbit grazing. The heat was getting to me, despite the wet hat. The violence of the heat here scarred the earth, whilst the sun struck from above and also from sideways and below, reflecting off the arid turf. Worrying signs of drought were also noted at Coombe Hill, further north in the Chilterns, where (diary) a tiny and unhappy colony of Duke of Burgundy based on exposed and droughted Cowslips at the foot of the slope (was) threatened by Rabbit pressure. Shortly afterwards that colony died out.

  In early August I carried out an approved reintroduction of the Silver-spotted Skipper to two large areas of suitable habitat on the downland massif of Butser Hill, south of Petersfield in East Hampshire, by transferring butterflies from Broughton Down in the west of the county. At the time scientific thinking held this to be a highly sedentary butterfly, incapable of colonising far-flung habitat patches. Twenty females and nine males were released on Oxenbourne Down, and eighteen females and ten males in a deep combe called Grandfather's Bottom. The release was sanctioned by the Nature Conservancy Council, Hampshire Wildlife Trust and Hampshire County Council. Unfortunately, a spell of cool and wet weather set in almost immediately, which relieved the burgeoning drought conditions but was not good for the skippers. The long and short of it was that the butterfly definitely took to Oxenbourne Down but was not adequately searched for on the precipitous slopes of Grandfather's Bottom. Then, the butterfly went into a major expansion phase and colonised the area naturally, probably from populations in the Meon valley a few miles to the west. One of the main conclusions from a review of butterfly introductions in Britain which Martin Warren and I published in 1990 was that, historically, a great many introductions had taken place just in advance of, or even at the same time as, periods of natural spread. Here, I was hoist with my own petard, so to speak, though this particular release was based on the scientific evidence that existed at the time; it is just that the skippers, taking advantage of climate change and the resurgence of grazing on the downs, suddenly moved the goalposts. These changes have been well documented by Professor Chris Thomas.

  Late in the second week of August the Clouded Yellows came in, accompanied by a fair few Painted Ladies. As a birthday treat I was offered the choice of having a party or going to the seaside. Given the weather, it was a no-brainer, so off we went to Compton Bay on the Isle of Wight for the day. The first butterfly seen on the cliffs was a Clouded Yellow. Shortly afterwards another came in low over the sea, and hurtled up the cliffs at great speed. By mid-afternoon at least ten were present on the cliffs, feeding avidly on Fleabane flowers. There is little I would like more for a birthday present than a Clouded Yellow immigration. Strangely, though, the females did not seem to be interested in laying eggs, in contrast to the influx witnessed at the same place in June 1983. Painted Ladies and a couple of Red Admirals were also seen flying in low over the sea. ‘Welcome to Britain!’ I said to each and every one in my best Margaret Thatcher voice, stamping their passports and sending them on their way.

  On August 15th the weather broke, though only for five days, producing the first effective rain in the south since July 6th. By the end of the day the lawns had visibly greened up, for brown lawns and fields almost instantly flush green again after a drop of rain. But by late August the drought had reasserted itself, especially on the thin chalk-soil slopes of the North Downs in Surrey. A visit to the Reigate downs with Gail Jeffcoate revealed desert-like conditions.

  Diary, August 28th 1990: Juniper Hill is quite the worst Rabbit drought-scape I've yet encountered. Incredibly hard-grazed and droughted. Some 40–50 per cent of the slope is bare, with a stunted flora just managing to survive – bald-toothbrush tussocks of Sheep's Fescue Grass, tiny hard-grazed Tor-grass tussocks, and a prostrate carpet of Common Rockrose. Upright Brome Grass has been grazed out.

  A little further east the slope had been grazed hard by sheep during the winter, for conservation, and the Rabbits had moved straight in and turned it into another
‘Rabbit drought-scape’. Similar problems were seen at Denbies Hillside, the scarp slope across the Mole Gap from Box Hill. Again, well-intentioned conservation grazing had been grossly exploited by Rabbits. In effect, conservationists were wanting to ‘coppice’ the grassland – graze it down and let it grow up again more modestly – only the combination of drought and Rabbits was preventing any regrowth and generating visions of desertification. Of course, after a couple of strong grass growth seasons the turf recovered well. We had seen drought impacting on the downs before, notably in 1976, only then Rabbits were still at a low ebb. During the 1980s Rabbits recovered in many places, just as sheep and cattle grazing was being restored to many nature conservation sites. The irony was considerable.

  Overall, 1990 saw the hottest August in Britain since records began in 1659, and the summer period (June, July and August) was the ninth warmest of the century. Gradually, summer eased away during September as cloud and showers took over, the cracks and fissures disappeared and the fields and lawns turned green again. On many of the thin-soil chalk downs in the South-east, though, the Rabbits had taken over, and their vision was to restore the downs to pre-myxomatosis conditions. There were unexpected challenges for conservation here.

  18 Moving on

  New Year is often a time of illusion, or even self-delusion. Caught up on a wave of optimism we misread the signs, assuming they were signs in the first place. The truth is that New Year is in the wrong place: it should either be the day after the winter solstice or when the Rooks start building, though the latter is a variable feast. No wonder signs are misread and resolutions quickly abandoned.