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CONFERENCE '94 'Butterflies in a Changing Countryside' The fourth Annual Conference of the Suffolk Naturalists' Society, entitled 'Butterflies in a changing countryside', was held on Saturday, 30th October 1994 at the Ipswich School Conference Centre. The event was co-hosted by Forest Enterprise and supported by Butterfly Conservation, Suffolk Wildlife Trust (SWT) and Ipswich Borough Council. Opening the Conference, the Chairman of English Nature and patron of the Suffolk Naturalists' Society, the Earl of Cranbrook, outlined the ränge of environmental issues threatening the existence of butterflies. He described the importance of butterflies as the 'Standard bearers' of threatened habitats and the significance internationally of the U.K. Bio-diversity Plan and the role played by butterflies in it. Lord Cranbrook congratulated the organisers on the conference and the support it had attracted and described the value to nature conservation of the enterprise that it demonstrated. The Chairman ofthe morning session, Mr. G. Hatfield, Regional Direclor — North & East England for Forest Enterprise. Mr. Hatfield gave a brief introductory talk outlining the role of Forest Enterprise within the Forest Authority, describing the value of the conference in helping to strike a balance between the wide ränge of interests shaping the multi-purpose management strategy adopted by them. Butterflies and multi-purpose forest management — Rod Leslie, Regional Environment Manager and national spokesman for Forest Enterprise. The Speaker outlined the scale of the Forest Authority's estate in Britain and the importance the Forest Authority attached to it for providing a diversity of wildlife habitats. A total of 27,000 hectares of forests provided the opportunity for habitat management on a large scale. Examples of successes for specific species of butterflies included those for Heath, Silver-washed and Duke of Burgundy Fritillaries. In Suffolk, a programme of sympathetic management over the 270 hectares of Rendlesham Forest had increased the number of species supported from 12 to 34. The authority will encourage the Silverstudded Blue to return. Butterfly populations had responded to the good, wide rides that had been established. Rod Leslie emphasised the very careful planning of habitat management undertaken by the Authority and the study of the effects of work on butterflies. The need to provide a succession of suitable habitats for butterflies had been recognised and the limitations of certain management regimes for achieving this, particularly those which did not provide adequately for the clearance of cut material. Experience had under-pinned the value of coppice for butterflies and the ground flora that supported many of the scarcer species. Setbacks were being caused by excessive grazing by deer in coppiced areas. Controlled high forest felling had produced results botanically similar to coppicing. He reported the success of a project to develop populations of Black Hairstreaks that involved the help of English Nature and Butterfly Conservation. The Authority recognised the value of amateur studies, like those encouraged by the Suffolk Naturalists' Society, and the Speaker announced a forthcoming scheme to offer grant aid to those engaged in such work.
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Woodland butterflies — the decline of traditional management and the Potential of new plantations — Dr. M. S. Warren, National Conservation Officer for Butterfly Conservation. Martin Warren introduced his subject by describing the importance of woodland habitats for butterflies; three-quarters of all species can occur in woodland. The management of Bradfield Woods illustrated the features that are important for woodland butterflies, with coppicing producing varied conditions. The condition of types of woodland that support specific species influences their fortunes. Populations of species like the Purple Emperor are supported by a canopy that is slow to change, but Heath Fritillaries in chestnut coppice are excluded after six years of stool regeneration. The recent expansion of the White Admiral was considered to be partly in response to sympathetic woodland management, as was that of the Wood White in coniferous areas. Vetches that support many of the important butterfly species are particularly sensitive to shade and will decline rapidly where unchecked growth exists. For certain species, like the High Brown Fritillary, eggs and larvae require very hot microclimates (50°C) associated with bracken among moss and rocks to develop. The Speaker described the need of many species to find and recolonise woodland habitats at a particular stage of development. This had been possible for them in former centuries when coppicing of woodland had taken place on a five-year rotation. In more modern times there had been a rapid decline of coppicing since 1950 and a need to restore traditonal coppicing wherever feasible, and to protect the coppice from deer with dead hedge fencing. High forest cannot provide a succession with any degree of certainty. Woodland rides are important for sustaining the continuity of butterflies, but knowledge about ride management is still rudimentary. Enthusiasm for ride management often wanes and more studies are needed on the effects of different machinery used. The most beneficial time for cutting may be summer and there is a need to investigate the effects of more radical management regimes like rotovation. Martin Warren sounded a warning about the status of the Pearl-bordered Fritillary which had been declining by 50% per decade. The use of 'bays' in woodland habitats, which were often cleared and then neglected, was not the answer. Finally, the Speaker drew the audience's attention to the 'Woodland Campaign' to be launched by Butterfly Conservation in 1994. The Large Blue and other grassland butterflies — Dr. J. A. Thomas of Furzebrook Experimental Station, broadcaster and author. Jeremy Thomas described the fortunes of grasslands as habitats for butterflies as being similar to those of woodland, with a rapid deterioration of their extent and diversity in modern times. For 6,000 years the pattern of agriculture had sustained large acreages of grassland for animals to graze. There were also meadows to provide hay for animals in winter. Grasslands throughout Europe had been subjected to 'improvement' through the application of chemical fertilisers and changes in mowing regimes. These had enhanced the growth of grasses to the exclusion of other plants which had sustained a variety of butterflies. There was some evidence that the increase in level of nitrates had lead to the expansion of nettles, enhancing populations of nettle-feeding butterflies, particularly in Holland. The greater productivity of agriculturally 'improved' areas and the decline in Trans. Suffolk Nat. Soc. 30 (1994)
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the number of grazing animals had also led to the abandonment of areas of grassland, which had then become overgrown. The Speaker described how grassland species need turfs of specific lengths, with long grass excluding all but skippers. Many species that were dependent on the plants that existed among the short-cropped grasses of the traditionally grazed meadows had become threatened by changes in grassland recently. There is a need to conserve ancient grassland. Recent research has revealed that the Brown Argus demands foodplants in a specific condition. Plants chosen for oviposition need to have 'fat' leaves with a high nitrogen content. Ants have a significant role in the ecology of a third of grassland species, and the Speaker emphasised the importance of rabbit grazing in areas that supported species associated with shorter turf. like the Adonis Blue. High temperatures promote populations of the 'short' species that are generally at the northern edge of their ränge in Britain. Short turf and high temperature also sustain ant populations that support many of the 'short' species. The Large Blue, and its re-introduction to Britain, are subjects that many of the audience associated with Jeremy Thomas and the presentation gave the Speaker an opportunity to illustrate some aspects of the ecology of that species. In conclusion, Jeremy Thomas stressed the importance of creating different types of habitat to conserve butterflies. The work done to manage habitat in support of the Large Blue has enhanced the populations of many other valuable butterflies and plants. Butterfly introductions and re-establishments — why?— Matthew Oates, Advisor on Nature Conservation for the National Trust and Conservation Committee Member for Butterfly Conservation. Matthew Oates offered some controversial perspectives on the subject of butterfly introductions (an 'introduction' is an attempt to establish a species in a place where it does not exist), and described changes in the understanding of the subject. The recognised 'Code of Conduct' for the introduction of insects is considered to be out of date. The urge to introduce butterflies was present long before it was seen as a conservation tool. Butterflies were a populär hobby with the Victorians. They collected them, attempted to produce aberrant strains and, to enhance their hobby, made some introductions, but with no knowledge of butterfly ecology. It was not until 1981 that it became illegal to introduce species not native to an area. Why introduce? Extinction is a natural process. However, there is always a desire to make releases into the wild. In view of the harm that uncontrolled action can bring it is constructive to try and influence such activities so that they are favourable to the species and the associated wildlife at the point of release. Fragmentation of wildlife habitats by development and agricultural practices means that many species have become vulnerable in isolation, and often lost. Where it was possible to manage isolated fragments of habitat in which a species would not normally be viable, is it reasonable to sustain a species' viability with introductions? There is no evidence that butterfly introductions have done any positive harm to either their old habitats or their new. The 30% success rate achieved by introductions will be improved. The justification for re-introducing an 'extinct' species, especially one that is a recognisable variant, may have been based on limited inteiligence about the Trans. Suffolk Nat. Soc. 30 (1994)
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status of the resident variety. The 'extinction' may not actually have taken place but could have been precipitated by the arrival of the introduction! Introductions may be unnecessary; butterflies can regenerate themselves without the arrival of ' f o r e i g n ' stock. This has been demonstrated by the recovery to 1970 levels of the populations of the White-letter Hairstreak, in spite of the demise of its foodplants through Dutch Elm Disease. Matthew Oates ended on a personal note with a plea that conservation Problems should not be handed down to our children. Introductions should be seen only as part of any conservation strategy and releases should only be made to re-establish butterflies where population can be expected to expand. W h e r e threatened species exist in a secure area they should be conserved in situ and not moved elsewhere. H e supported the principle of the Swallowtail being introduced to Wicken Fen and the Large Blue to their undisclosed site. Finally, he stressed the importance of adequate scientific investigation before butterflies are removed from any d o o m e d site. Taking the Chair of the afternoon, Dr. R. E. (Bob) Stebbirtgs, Suffolk Naturalists' Society, introduced the first Speaker.
President
ofthe
Climate and butterfly distribution — Dr. T. G. Shreeve, lecturer in Ecology at Oxford Brookes University. The Speaker reviewed the dire predictions of climate changes and the effects of climate on butterfly ecology. It is uncertain whether climate changes effect different species alike or not. Changes in broad climate and micro-climate conditions could both result in extinction and recolonisations of butterflies. Tim Shreeve referred to the shortage of ecological information about butterflies, but it is accepted that temperatures between 28°C and 38°C are crucial for adult activity. The differences between the way individual species bask was illustrated by the Speaker: Small Tortoiseshells are 'dorsal absorption baskers', Graylings 'lateral absorption baskers' and Green-veined Whites 'reflectance baskers'. Small butterflies warm up quickly, but achieve a less stable body temperature than larger species. T h e need for butterflies to regulate their body temperatures affects predator/prey relationships; when they are basking or drinking they are vulnerable to attack. Climate can influence butterfly populations by its effect on larval food plants. Any change in climate is likely to be a gradual increase in temperature. This would results in greater changes in northern areas and in winter. A northerly migration of species would be predicted with the rising temperatures, although the extent to which all of them could move is uncertain. Generally the climate change is expected to be beneficial to butterflies in Britain, although there would be a decline in bog species. The rise and fall ofthe Holly Blue — Tina Yates, co-ordinator of the National Butterfly Monitoring Scheme at the Institute of Terrestrial Ecology at M o n k s Wood. Tina Yates described the changes she had seen in the population of the Holly Blue in Britain over the 17 years she had been engaged upon the National Butterfly Monitoring Scheme. Many questions remain unanswered. It is unclear whether the species has two distinct generations and the larvae are not entirely dependent upon berries or
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any particular foodplant. A variety of foodplants, in addition to the accepted ones of Holly and Ivy, are capable of supporting the Holly Blue. She described how counts were made by recorders involved in the Monitoring Scheme, operating since 1976 and colloquially known as the 'Pollard Walk', after its originator, Ernie Pollard. The Speaker illustrated the classic Holly Blue 'boom' and 'bust' between 1984 and 1990. Not only was there an expected increase in populations during the 'boom' years but also a northward expansion of the species. The northward expansion was still taking place when southerly populations were 'crashing'. Tina Yates accepted that Holly Blue population 'crashes' were neither wholly attributable to climate or to predation by parasitic wasps. The familiar pattern of population cycles of the Holly Blue was not necessarily bound to continue. The whereabouts of the species in the years following a 'crash ' is unknown. Are there stable populations somewhere to provide seeds for the following 'boom'? History and future of the Swallowtail in Britain — Dr. J. P. Dempster, University of Cambridge Director of the Institute of Terrestrial Ecology (South) (retired). Jack Dempster described the former widespread distribution of the Swallow tail in Britain and compared it to the present confined broadland sites. The Swallowtail existed throughout the world and was common in some countries. The historical account of the British strain had been confused by frequent immigrations of Continental butterflies. Although they are very similar in appearance, Continental strains of Swallowtail differ significantly from the British in being very mobile, existing in arid habitats and being supported by a variety of foodplants. The larvae of immigrant Swallowtails in Britain feed on carrots, fennel and rue, but second generations fail during winter. Several factors are associated with the decline of the British strain. Milk Parsley, its favoured foodplant, is dependent upon wet habitats and has become rare with the decline of fenland. By 1850 Wicken Fen had been reduced from 4,000 to 1.3 hectares. Peat removal had then created some suitable habitats on the margins of the broads that had formed, but more recently these have become dryer and more scrubby. A rapid fall of Swallowtail populations followed the very hot and dry summer of 1976. Larval mortality is high. The larvae have specific feeding requirements, grazing on the upper surfaces of leaves as young larvae and on flowers when mature. Although exposed when feeding they are well camouflaged as bird droppings, but 70% larval mortality of British populations has been attributed to arthropods, with a further 25% in winter from uncertain causes. Butterflies now have an enlarged thorax compared with specimens collected at the turn of the Century, suggesting that the species has recently evolved, with a decreased capacity for mobility. The fact that an attempt to re-introduce the Swallowtail at Wicken Fen in 1975 had failed because females did not lay eggs should not prevent further efforts. The condition of the fen has improved since 1971 and its potential for another trial should be investigated. Swallowtail habitats should be managed by cutting of herbage in spring rather than summer, and peat should be cut to meet the water table. 'Pretty big' areas of habitat should be planned to sustain
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populations and it should be noted that successful Norfolk sites had a density of 5,000 foodplants supporting five females on each hectare. Silver-studded Blue — the future of isolated populations in Britain — Dr. C. D. T. Thomas of the University of Birmingham. The Speaker described the seriously reduced ränge of the butterfly. Pre-war records showed it extending to Scotland. It had latterly been confined to a few sites in North Wales, East Anglia and the South Coast of Britain. In former times the species existed as a small number of recognisable races, supported by a variety of habitats and foodplants. One of the races associated with chalk grassland of the South Coast of Britain can no longer be found. The decline of the species cannot be attributed to a shortage of foodplants, which were relatively common, including Bird's-foot Trefoil, Rockrose and heathers. Favoured habitats have broken ground with short turf and eggs are usually laid at the boundaries of plants at the rate of 100 to the Square metre. Pupae had been found beneath rocks. The association of the Silver-studded Blue with ants has been known since Victorian times, but their precise role in the butterfly's ecology is still not fully understood. The enigmatic oviposition of the species on Bracken, linked to the trails of ants, was first revealed in an amateur study by members of the Suffolk Naturalists' Society in 1987. 'Moonscapes' replaced landscapes as 'ant's-eye' views of the body surface of larvae were provided by electron photomicrographs. They show previously unknown organs, the function of which is thought to be linked to the butterfly's relationship with ants. Chris Thomas commented upon some of the factors in habitats which favour the butterfly. The importance of 'hot spots' and microclimate had been identified and often south-facing slopes were preferred. Heathland is in a constant State of change and there is a need for a succession of suitable habitats to be available in the proximity of existing colonies. The species should considered in terms of 'meta-populations' — concentrations of sedentary butterflies needing to shift their locations over short distances as the flora of sites outgrow them. Rabbits help to maintain a suitable habitat, and they should be encouraged. Areas supporting Silver-studded Blues need to be at least 100 hectares. To summarise, the conference Chairman, Bob Stebbings, spoke of the value of butterflies as a 'barometer' of the abundance of wildlife. Butterflies seen in sparse numbers in recent times were seen in large numbers when he was a child. Many speakers at the conference had stresses the gaps in knowledge about many species and highlighted the need for more ecological studies of butterflies to be made to determine effective conservation management. There is often difßculty in balancing the demands of conflicting interest when managing habitats. Many butterfly species are dependent upon large areas of habitat to provide a rotation of places in the right condition to sustain viable populations. Large forest estates controlled by the Forestry Authority are being managed in a way sympathetic to the needs of threatened wildlife. He found the prospect of fragmented habitats resultings from 'privatisation' of the forests, being promoted by the present Government, 'too horrendous to concede', and urged the
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audience to campaign against it. Bob Stebbings thanked all who had supported the conference and announced that the subject of the 1994 event would be 'birds'. Eric Parsons
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