The Butterfly Monitoring Scheme (BMS) dataset does not show how abundant butterflies were that year. Analysis of all the years within the scheme places 1976 some way down the hierarchy of excellence. Scientists are well aware of how inadequate Year One datasets often are, and the scheme was launched in 1976, with just a few places contributing. The truth is that reliance on BMS analysis sells the Long Hot Summer of 1976 terribly short. Hopefully this account goes a little way towards remedying that situation.
9 The legacy of 1976
It is difficult to determine the impact of the great drought of 1976 on our butterflies, as those effects were muddled up with those of the subsequent wet summer. Certainly, populations of several species declined severely in localities where their foodplants had succumbed to drought. On many southern downs, for example, populations of the Adonis and Chalkhill Blue butterflies collapsed, as their vetches had desiccated. On Noar Hill, Duke of Burgundy numbers in 1977 were half those of 1976, doubtless because a great many of the Cowslips on which its larvae feed had wilted; the Grizzled Skipper colony there vanished, for the Wild Strawberry plants it bred on frazzled up early on in the drought.
In 1977, spring ran late, though it produced a couple of good spells. May started promisingly but soon became plagued by convective cloud spreading across from the west mid-morning after clear cool nights. However, from the 18th high pressure developed, and dominated the remainder of the month. This proved to be the best weather of the whole butterfly season. During this period, it became clear that spring butterflies were nothing like as numerous as they had been the previous year, that they were emerging decidedly late, and that many colonies had simply vanished.
Most salient by its absence was the Speckled Wood, which normally started around April 20th in that era. Although I saw a singleton on April 27th the butterfly did not appear in any numbers before late June. Larval development had been hampered either by the drought or by the excessively wet autumn, or by both. Even more delayed was the Small Copper, which I did not see before August 11th – a good ten weeks late.
Butterfly of the spring in Hampshire was undoubtedly the Holly Blue, which appeared in even greater numbers than it had done the previous year. At one point I watched two pairs of Holly Blues mating some 20 centimetres apart on a Holly bush, whilst two other females were busy placing their eggs on nearby flowers. That was impressive, but the second brood, in August, was almost non-existent, the victim of an atrocious June.
During May, several hours were spent following Green Hairstreak females on Noar Hill, in the far chalk pit, up against the Beech hanger. The conclusion was that individual females of this distinctly polyphagous or catholic butterfly, which utilises a wide range of foodplants, were each selecting only a single species of plant: a couple of females laid only on Common Rockrose, after testing and rejecting other plants within the foodplant range, whilst others laid exclusively on Bird's-foot Trefoil. It might be worth someone developing this little study further, to explore the hypothesis that individual female Green Hairstreaks behave somewhat akin to female Cuckoos – or maybe this behaviour was merely the trait of an odd year?
June was dire, memorable for the rains that marred the Queen's Silver Jubilee. Punk rock was all the rage, led by the Sex Pistols’ nihilistic ‘Anarchy in the UK’. We were perhaps fortunate: the hit song in Maoist China was a ditty entitled ‘How I Love to Carry Dung up the Mountainside for the Commune’. June was the fourth wettest on record, and one of the coolest and cloudiest. By its end, buttercups were still well in bloom in the meadows, whilst in the woods brambles and thistles were only just budding up. Large Skippers and Meadow Browns emerged decidedly late, not appearing in East Hampshire until late June. Marbled White, Ringlet and Small Skipper only commenced at the end of the first week of July, whilst White Admiral and Silver-washed Fritillary did not appear in Alice Holt Forest until July 10th.
High summer belonged to the White Admiral, which emerged in superb numbers – despite the fact that its larval foodplant, Honeysuckle, had dropped its leaves the previous August, and despite the fact that Dr Ernie Pollard's research had found high levels of mortality amongst the pupae during cool wet Junes. Somehow the tiny larvae had survived the great Honeysuckle wilt of August 1976, and somehow the woodland Honeysuckle itself had (largely) recovered. But doubtless White Admiral numbers in 1977 would have been even greater had June been less inclement. Above all, this was the year in which the White Admiral produced a great number of variations, or aberrations. I personally saw 18 ‘Black Admirals’ in the Straits Inclosure of Alice Holt, at least two of which were the excessively rare all-black version, ab. nigrina. Well into August White Admirals were skimming the edges of each and every glade in Alice Holt, often in twos and threes, summoning each other from afar, and meeting up briefly before continuing their lone pilgrimages.
That July R W (Robert or Bob) Watson, the last of the great New Forest collectors and a glorious eccentric, appeared in Alice Holt Forest in pursuit of Black Admirals. A Forest man born and bred, he worked as a milkman and even as a prize fighter before becoming an accountant. Women, though, were his nemesis. He married five times, each time unsuccessfully. Early in March he would hold an open weekend at his house, at Sandy Down near Brockenhurst, for anyone with an interest in butterflies or wider Lepidoptera. Other doyens of the final era of New Forest collectors gathered there, notably the butterfly artist A D A Russworm and Rear Admiral A D Torlesse. Watson was a most generous host, if a little over-interested in escorting young men's girlfriends around his garden, on the pretext that he wanted to show the young ladies his plums (or was it grapes? Either way they were seriously out of season in March, and at least one young lady stated that the experience was akin to an outing with Benny Hill). He was obsessed with pigs, naming his house Porcorum, after the Latin for pigsty. He passed away, rather spectacularly, in 1984. One should not promulgate rumour, so the following account must be offered as fact, safe in the knowledge that Bob himself would thoroughly approve. Having being advised by his doctors in the strongest possible terms to avoid alcohol (his personal intake consisted of a bottle at lunch and at least one at supper) he partook somewhat splendidly at the Royal Entomological Society's annual Verrall Supper, only to pass out on the steps there, supported by two fellows’ wives. That is precisely how Robert Watson would have wanted to depart this mortal coil. His immaculate collections were bequeathed to the nation.
For the most part, a veil needs to be drawn over the 1977 Purple Emperor season. It appeared absurdly late, scarcely getting going before July 24th. Larval development had been retarded by the wet June – I found a full-grown larva on Midsummer Day. The Emperor season did produce some magic moments, however: notably a frenetic few minutes on July 30th when half a dozen males were seen in a vista, attacking anything on wings, whilst two Black Admirals, including a full ab. nigrina, floated innocently by. In Alice Holt, a few females lingered into September, the last being recorded there on the 7th, a record for the modern era.
If the Purple Emperor was poor in 1977 the White-letter Hairstreak was even worse: I saw none all season, for I knew of no surviving mature elms. More curiously, the Ringlet was scarce for several years on Hampshire's downs after the 1976 drought. Somehow, though, the Brown Hairstreak emerged in exceptional numbers at Noar Hill in September, almost redeeming a rotten summer.
Alice Holt Forest
People need trees, though whether trees need people is another matter. We have a special relationship with forests, for we were once forest people – though we have largely cleared our forests away. That relationship has a metaphysical dimension, which often extends to particular forests and wooded places – the sacred grove of Greek mythology.
In the 1970s much of Alice Holt Forest, an 851-hectare (2100-acre) expanse of woodland on the Hampshire/Surrey border, was a secret and shadowy place. Public access was tolerated in most of it, but was by no means encouraged, and naturalists had to apply for an annual access permit – to be shown o
n demand. The Forestry Commission, which runs the forest, wanted primarily to grow trees, shoot deer and meet financial targets imposed on it by the Treasury.
Historically, entomological activities in Alice Holt concentrated on the Lodge Inclosure, in the north-west of the forest. ‘The Lodge’, as it was known in butterfly-collecting circles, lies close to Bentley Station, which enabled field-meeting parties from London to descend on the place. Baron de Worms himself started to lead excursions of the British Entomological Society there before the Second World War.
By the mid-1970s a few butterfly enthusiasts had explored beyond Lodge Inclosure and discovered Straits Inclosure, in the south-west part of the forest. Straits Inclosure was by far the wildest and least frequented part of the forest. It lies on Gault Clay, a heavy thug of a clay that turns to cracked and fissured concrete during summer droughts and intractable glue in the wet. It grows good-quality oak, but timber extraction is extremely difficult. In effect, forestry operations are only viable there during periods of sustained drought. The surfaced main ride, ‘New Ride’, now frequented by butterfly photographers each July, was installed early in 1987 to facilitate the Forestry Commission's thinning and harvesting programme. But throughout the 1970s there was only one L-shaped grassy open ride, which was opened up in 1970, and some narrow linear glades along overhung rides. These rides were dominated by huge tussocks of Tufted Hair-grass that rendered walking difficult. The place hummed with clegs and other biting flies in high summer. Bramble patches were frequent, though mainly in dappled shade. The understorey of Hawthorn and Hazel was draped in vast tangles of Honeysuckle. Tall sallows lined many of the rides, and were profuse amongst the younger blocks of oak woodland. Turtle Doves purred in the distant shade. Traffic noise was absent. It was a world apart. The inhabitants of nearby Frith End were largely ex-colonial types who did things colonially, like mass fly-mowing on Sunday afternoons, and seldom ventured into the wood.
The inclosure is some 80 hectares (200 acres) in size. It had been replanted extensively with oak during the 1930s, though some curious narrow bands of Norway Spruce were added, which blew down spectacularly in the great storms of January 1990. The mess was cleared, and the bands left to natural regeneration. They are now choked with sallows and other young broad-leaved trees. A small plantation of Corsican Pine, established in 1965, survives on the west edge. Efficient deer management has meant that the growth of the Hazel and Hawthorn understorey is vigorous. It is this shrub layer that holds the Honeysuckle tangles on which the White Admiral breeds.
The Gault Clay also comes to the surface in Goose Green Inclosure, across the Frith End road from Straits Inclosure, and further east across the busy A325 in Abbots Wood Inclosure. These inclosures too are primarily oak country, holding remnant stands of oaks planted in the 1820s for navy timber. At the southern end of Abbots Wood Inclosure is an area of some 10 hectares that was clear-felled in 1981 and replanted with oak, much of which failed or was out-competed by broad-leaved natural regeneration. For many years this clearing held sizeable colonies of the two spring-flying pearl-bordered fritillaries, along with Dingy and Grizzled skippers, before sallows grew up and converted it into a massive Purple Emperor breeding ground. The Gault Clay also extends northwards along the western edge of the forest into Lodge Inclosure.
Much of the forest lies along a transition line between the Gault Clay and the Tertiary sands. The northern and north-eastern inclosures lie on former heathland. These sandier areas have been vigorously exploited for growing conifers, though old oaks still fringe the inclosure margins. The butterfly interest is primarily associated with the more clayey areas. Clearings and young plantations on the sandier soils tend to be utilised more by Nightjars than by butterflies.
In the late 1970s the Forestry Commission designated the Straits Inclosure as a Conservation Area, primarily for the Purple Emperor and other butterflies. That internal designation did not actually mean much, as few funds were available for conservation work, though some ride widening and glade creation was carried out in the late 1970s and early 1980s, and a large pond was created along the southern edge during the 1977/78 winter. The pond failed to contribute towards the conservation of the existing wildlife interest, and drained the conservation budget. In time it will silt up and grow sallows, and Purple Emperors.
My diaries document the highs and lows of ‘the Straits’ over nearly forty years, and record some of the most wonderful events of my life as a naturalist and butterfly lover. They chronicle the highs and lows of three butterfly species in particular, Purple Emperor, White Admiral and Silver-washed Fritillary. I have kept a record of every sighting of Purple Emperor, whilst White Admiral and Silver-washed Fritillary have been monitored through rough timed counts during their peak season periods along the more open sections of ride, which have of course changed from era to era due to ride creation, widening and canopy closure. The problem with such data is that route, time and distance have varied considerably between different epochs.
In effect, there have been four distinct monitoring phases: the period 1975–1982, during which there was only some 300 metres of open L-shaped ride; 1982–1987, after the open ride system had been extended to the wood's centre; from 1987, when ‘New Ride’ was cut out, to the late 1990s, when there was a triangular route of open ride that extended for almost a kilometre; more recently, parts of this system have closed over, only to be reopened. Above all, my records track massive and often horrendous change, whilst illustrating the difficulties of consistently monitoring butterfly populations in dynamic woodland environments.
It is probable that I discovered the Straits at the end of its golden era: would that I had known it during the 1960s, when Purple Emperor and White Admiral must have abounded! Duke of Burgundy and Pearl-bordered Fritillary, Dingy Skipper and Grizzled Skipper all died out from the west-edge conifer plantation after 1976, though Small Pearl-bordered Fritillary lingered on until 1980. A small colony of Wood White, established in July 1976, lasted until 1981. It might have thrived had its favoured ride not been pulverised by timber hauling associated with pond creation during the 1977/78 winter.
Major ride widening took place in August 1982, to prepare the site for timber extraction. In late July 1983 heavy thinning work started in the eastern half of the wood, and an era of entomological greatness ended suddenly. This work was hugely exploitative and took no obvious account of nature conservation interests. Most of the mature sallows in the wood's eastern half were felled during three summers of thinning and harvesting. The impact on the Honeysuckle tangles beloved of the White Admiral was equally acute. Purple Emperor and White Admiral populations collapsed, despite a sequence of three good summers.
Tufted Hair-grass increased strongly when the oaks were thinned. This could have adversely affected the Silver-washed Fritillary, which breeds on violets beneath the oaks. Yet, the opposite occurred, for after modest seasons in 1984 and 1985 paphia exploded in the wood: the 1986 emergence is still the best on record for the Straits. Also, Essex Skipper invaded the open grassy rides in numbers, before dying out in the 2000s.
The Straits showed impressive indifference to the 1987 ‘hurricane’, and sallow regeneration was encouraged along the newly cut-out broad New Ride. However, thinning work got into full swing in the remote western half of the wood during the summer of 1988, at a time when July butterfly populations were falling due to bad midsummer weather. By the end of 1988 nearly all the mature ride-side sallows had been felled – long before they would have been out-competed by taller-growing trees.
After a short lull, thinning work returned with a vengeance in 1991 and I wrote mournfully in the diary: I think I've seen the last of iris here. I was wrong, of course, for the following year thinning ceased and the sun shone. I saw my first Straits Emperor for six years. Even better, White Admiral resurged in the eastern half, which was recovering nicely from collateral damage incurred during thinning works. Matters improved further in 1993, especially for Silver-washed Fritillary, wh
ich had a bumper year. The following year brought the first Black Admiral for eleven years, and an encouraging flight of Purple Emperor.
But heavy thinning work returned with a vengeance in 1996, and Straits Inclosure was abandoned as a conservation area and de-prioritised for nature conservation by the Forestry Commission as it was not a Site of Special Scientific Interest (SSSI). Again, White Admiral and Purple Emperor populations collapsed; the former to the point of near-extinction, whilst the latter became dependent on the young New Ride sallows. At this inapposite time, the Purple Emperor was adopted by the Forestry Commission as the symbol of its new commercial creation, Alice Holt Forest Woodland Park. A visit in perfect weather on July 17th 1999 revealed a wood almost void of butterflies, as populations of both White Admiral and Silver-washed Fritillary had plummeted. The Straits entered the new millennium at an unprecedented nadir, especially as the harvesting work had failed to open any of the overhung rides. I could scarcely visit, the experience being too painful, the desecration of spirit of place and personal memory too great.
There then began seven peaceful years, during which vegetation and butterflies recovered from the maelstrom inflicted by Euroforest, the Forestry Commission's contractors. Of course, vegetation conditions recovered ahead of the butterflies, which meant that 2001 was a particularly bleak year for Silver-washed Fritillary and White Admiral – the latter was not recorded at all, and only produced a singleton in 2002. Yet all the while the Emperor population was rebuilding. The great summer of 2003 saw Purple Emperor breeding in the New Ride sallows. Populations of other butterflies were recovering too. The only gremlin was an infuriating bleeping machine, erected on a pole in the centre of the wood by Forest Research, contributing data to the Forestry Commission's Environmental Change Monitoring Programme. The good people of Frith End raised such a rumpus that the wretched thing was switched off, permanently.
In Pursuit of Butterflies Page 10