Many of these sites are owned by the National Trust, who graze them with cattle or sheep.

Habitat of Lulworth Skipper, Wall Brown, Marbled White & Dark Green Fritillary ï¿½ Adrian Hoskins

Wall Brown Lasiommata megera, Dorset coast – Adrian Hoskins

Erosion

Cliff faces, landslips and eroded slopes are of major importance to the Grayling and Wall Brown, whose larvae feed on fine grasses and require a warm microclimate. Other species which thrive on the steep slopes include the calcareous race of Silver-studded Blue on Great Orme, the Wood White in Devon, and the Glanville Fritillary on Wight.

The Glanville Fritillary is confined to coastal landslips on the south coast of the Isle of Wight – the only part of Britain where the climate is warm enough to support it ( although temporary colonies periodically appear on the Hampshire coast ). Landslip habitats are by definition transient, and only remain in suitable condition for the butterfly for a few years before becoming overgrown, so the colonies are short-lived and the butterfly depends on the creation of new landslips for it’s continued existence.

Glanville Fritillary Melitaea cinxia, male, Wheelers Bay, Isle of Wight – Adrian Hoskins

Heathlands and moors support quite a limited range of butterflies, mainly amongst the Satyrinae, Lycaeninae, Polyommatinae and Hesperiinae.

Controlled burning

Some heaths, such as those in the New Forest and Exmoor are traditionally grazed by ponies; but controlled burning is the primary heathland management tool. Areas that are not periodically burned become very overgrown with heather, gorse, birch and young pines, and eventually revert to woodland.

Burning releases nitrates, and allows the habitat to regenerate, producing fine grasses, trefoils, milkworts and a carpet of fresh young cross-leaved heath, foodplant of the Silver-studded Blue. Fires can get out of control, so heaths nearly always have a network of wide firebreaks, and these are mown periodically, producing a mix of fine grasses and exposed soil, which is favoured by Satyrines such as the Grayling and the Small Heath.

Silver-studded BluePlebejus argus – a typical heathland butterfly, still found in thousands on certain heaths in Hampshire’s New Forest – Adrian Hoskins

Colonies of the Grayling Hipparchia semele occur on dry heathlands in southern England, and on coastal grasslands throughout Britain – Adrian Hoskins

These and many other wild flowers such as marjoram, thyme, knapweeds, self heal, germander speedwell, buttercup, dandelions and daisies are also extremely important as nectar sources for the adults.

Finally of course are the grasses – fescues, bents, couch, timothy, Yorkshire fog, wood false brome etc; which are the larval foodplants of various Skippers and Browns.

Chalk grassland at Cerne Abbas, Dorset, England – Adrian Hoskins

Extensive areas of calcareous ( chalk or limestone ) grassland such as the South Downs, North Downs, Chilterns, Malvern Hills, Purbeck Hills and Cotswolds can support enormous butterfly populations, but even small areas of grassland, in woodland clearings, along railway cuttings, in meadows and in abandoned chalk quarries are of immense value if suitably grazed and managed.

Disused railway line running through chalk grassland and woodland, Dorset – Adrian Hoskins

Grazing and scrub control

To ensure the continuing survival of a wide diversity of butterfly species, it is essential to manage grasslands so that they support a variety of different vegetation types.

Management has to be tailored according to the situation – some sites, because of their situation, can only be managed by mowing or flail cutting, but cattle or sheep grazing generally creates much better conditions for butterflies.

Sheep graze in a manner which produces a uniformly fine sward, with a profusion of vetches and trefoils, and creates a habitat particularly suitable for certain blues and skippers.

Cattle grazing, in conjunction with scrub control measures, has been shown to be the best overall management technique however, as the grazing pattern tends to create a mosaic of different sward heights, with a more diverse flora that accommodates a wider range of butterfly species.

The timing of grazing is extremely important – summer grazing can for example have a detrimental effect on species which spend summer in the larval stage, feeding on grasses or herbaceous plants.

Wild rabbits are of immense value as natural grazers, particularly as their excavations expose patches of bare soil where butterfly foodplants can germinate. Periodic surges in rabbit populations however can result in severe over-grazing that can easily wipe out certain butterfly species. Stock densities of cattle and sheep therefore need to be carefully tailored to take account of the effects of rabbit grazing in any particular year.

Another consideration is that each species of butterfly has different requirements  – some need the grasses to be lush and tall, while others need it to be very short. The Adonis Blue and Silver-spotted Skipper for example will only breed at warm sites, favouring south facing slopes where the grass is short and sparse.

Chalkhill Blues, Small Coppers and most other grassland butterflies need a slightly taller sward of about 10cms, where the habitat is moister and rich in wild flowers. Most of the Satyrinae and Hesperiinae on the other hand require a sward of between 15 – 30cms.

Getting the balance right, to create a habitat that will support viable populations of a wide variety of species, can be very difficult particularly if the site is small. Unfortunately it is sometimes necessary to prioritise and cater for one particularly scarce species at the expense of another. On larger sites this is less of a problem because different parts of the site can be grazed at different times of year or at different livestock densities, to cater for a multitude of butterfly and moth species, while at the same time providing habitat for other forms of wildlife.

Ramsdean Down, Hampshire – Adrian Hoskins

It is not only the grasses and wild flowers that need to be managed – a site left unmanaged would within a few years become overgrown with bramble, privet, dogwood, buckthorn, gorse, hawthorn and blackthorn bushes which would shade out the herbaceous plants and grasses. Eventually the site would revert to woodland, and all the wild flowers and grassland butterflies would disappear.

Bushes therefore need to be periodically cut back – a process known colloquially as ‘scrub-bashing’. It’s very important however to get the balance right, because a certain amount of bushy vegetation is beneficial to butterflies, providing much needed shelter from wind and blazing sunlight. Bushes also provide perching places which males use as lookout posts from which to survey and intercept potential mates.

Excessive scrub removal can cause major problems for butterflies, because many species lay their eggs on herbaceous plants that grow around the base of bushes.

If they laid their eggs on plants in open areas away from bushes, the resulting caterpillars would perish – either through desiccation in bright sunlight, or because rabbits would eat the plants on which they depended ( plants growing close to bushes are normally ignored by rabbits ).Grassland butterflies thrive best, both in diversity and abundance, at sites where a well considered grazing and scrub control regime produces a mosaic habitat in which bare ground, short turf, lush vegetation and bushes are all essential elements.

Hazel coppice with scattered mature oaks – a transitional woodland habitat ideal for species such as Pearl-bordered Fritillary and Duke of Burgundy – Adrian Hoskins

Transitional woodland

There are many different types of woodland in Britain, most of which are plantations of oak, beech or conifers, managed by the government agency Forest Enterprise. Only a small number of woods are now privately owned. Most of these are managed for timber, and a tiny number are coppiced.

In coppiced woods the trees are cut near the base of the trunk, which stimulates the growth of new shoots. The shoots are used mainly for hurdle making or charcoal production. Coppiced woodlands are of huge value as butterfly habitats. The regular cutting regime stimulates a continuous stable supply of larval foodplants and adult nectar sources. It also creates a warm sheltered environment that is ideal for butterflies.

Sweet chestnut. After 8-12 years the shoots reach a diameter of about 8″, and are harvested again.

Trees which are traditionally coppiced include hazel, sweet chestnut and hornbeam. Hazel coppice is particularly valuable as a butterfly habitat. The fallen leaves decompose very quickly, exposing the ground to direct sunlight, which stimulates the germination of violets, primroses, bugle, trefoils, wild strawberry and other larval foodplants. 

In sweet chestnut and hornbeam copses however the leaves decompose slowly, leaving a year-round carpet of dead leaves beneath the trees. This reduces light penetration and stifles germination of wild flowers. Consequently butterfly diversity and abundance is considerably lower than in actively coppiced hazel woodlands.

In most coppiced woodlands a small number of trees are allowed to reach maturity.

These include oak, ash and beech, sometimes supplemented by wych elm, lime or field maple. The shrub layer also invariably includes several incidental species such as buckthorn, hawthorn, blackthorn, sallow, holly and birch. A coppiced woodland thus includes a great diversity of trees, shrubs, herbaceous plants and grasses, providing foodplants for many caterpillars, and a variety of nectar sources for adult butterflies.

Butterflies confined mainly to transitional woodland habitats include Wood Whites, Heath Fritillaries, Pearl-bordered Fritillaries and Small Pearl-bordered Fritillaries. Many other species also use such places as supplementary or secondary habitats. These include Duke of Burgundy, Grizzled Skipper, Dingy Skipper, Holly Blue, Orange tip, Green-veined White, Brimstone, Peacock and Comma.

When coppiced woodland reaches maturity the amount of light reaching the forest floor diminishes, the herb layer virtually disappears, and butterflies are unable to continue breeding. Unfortunately most butterfly species have very poor powers of dispersal and rarely travel more than about 100-200 metres from their emergence site. It can take several years for successive generations to find a new breeding area. During the intervening years they struggle for survival, existing in only very low numbers, breeding along the edges of sunny woodland rides.

Woodland managers can help butterflies to win their struggle for survival by creating networks of sunny rides which can be used as migration corridors. If butterfly diversity and abundance are to be sustained it is vital that the coppice cycle is maintained. This ensures a varied age structure and diverse range of habitats, rich in the foodplants and nectar sources on which butterflies depend.

Conditions similar to those of coppiced woodland can be found in other transitional habitats such as the corridors of regularly cleared woodland beneath electricity pylons, or sunny railway embankments in wooded areas.

Ancient woodland

The New Forest in Hampshire is a unique area. It covers an area of over 57000 hectares which is largely managed by the government agency Forest Enterprise. It comprises of a mosaic of heaths, mires, pastures, conifer plantations and ancient oak / beech forest.

Records show that a century or two ago it was the richest area of Britain for butterflies, supporting a vast number of woodland, heathland and grassland species. Sadly that is no longer the case. Wild ponies and domestic cattle have been allowed to wander within the forest, and grazing has been so intensive that the herb layer of much of the area has disappeared, decimating butterfly populations.

Recently a more enlightened management policy has improved the situation. A small number of inclosures are now beginning to regain their former glory, with violets, bugle and other wild flowers reappearing. Consequently many species including Pearl-bordered, Dark Green and Silver-washed Fritillaries are now flourishing.

Mature oak woodland in the New Forest ï¿½ Adrian Hoskins

Broadleaf and conifer plantations

The vast majority of modern forests in Britain are plantations. Some are in private hands but most are state owned. These forests are typically broken up into small blocks of between 1-6 hectares in area, divided by firebreaks. Often several species of tree will be planted, but each individual block will consist of a monoculture of conifers such as pine, spruce, larch, cypress and fir trees.

Butterflies cannot survive in the gloom within conifer plantations, but when the trees are felled and sunlight once again reaches the forest floor, millions of dormant seeds germinate, carpeting the ground with violets, trefoils and bugle – the nectar sources and larval foodplants of butterflies. This abundance of food sources however is very short-lived, because within about 4 or 5 years, the new trees will have grown sufficiently to shade out the herb layer.

If butterfly colonies are to survive, it is vital that plantations are managed so that new clearings are created every year or two, to supply a continuous availability of suitable breeding habitat. It is also essential to give the butterflies a helping hand so that they can easily and quickly find their way to suitable new areas of breeding habitat. This can be done by creating wide sunlit rides which act as migration corridors between the forest blocks. Scalloping ride edges, and enlarging intersections provides additional temporary habitats where butterflies can breed.

Pine plantations are dark dismal places where butterflies cannot survive – Adrian Hoskins

Timber nowadays offers little financial return, and this fact, together with increasing public demand for leisure facilities has brought about a change in Government forestry policy. The tendency now is for the plantations to be periodically thinned, rather than clear-felled and replanted, and for the woodlands to become retained for their amenity value – many former timber plantations are now Country Parks.

The edges of the tracks and rides in plantations are often planted with a narrow strip of amenity broadleaves such as oak, sallow, buckthorn, field maple and wych elm. There are also often a few ornamental species such as scarlet oak, sycamore, lime and cherry.

Most woodland blocks are edged with drainage ditches and small embankments, while other habitats may include small semi-permanent glades, grassy avenues, riversides and ponds. A modern woodland is thus comprised of a multitude of sub-habitats which support many native trees, shrubs and bushes. The structure of the woodland usually ensures that there is an abundance of sheltered sunny areas, supporting a rich variety of grasses and wildflowers growing along the ditches, embankments and ride edges.

Wide grassy forest rides can be thought of as “linear meadows”. Vetches, trefoils and violets growing along the ride edges are used as larval foodplants by many species, as are buckthorn, sallow, dogwood and holly. Nectar sources also abound – hemp agrimony, thistles, bugle and bramble each attracting numerous butterfly species.

The consequence of this rich botanical variety is that many plantations in southern Britain support not only true woodland butterflies such as Silver-washed Fritillary, Purple Emperor, White-letter Hairstreak, Purple Hairstreak and White Admiral, but also often have populations of species normally associated with scrubby grassland – e.g. Dark Green Fritillary, Brown Hairstreak, Grizzled Skipper, Dingy Skipper, Large Skipper, Marbled White, Meadow Brown, Ringlet and Gatekeeper.

Most species however exist at very low densities and there is an absolute and immediate need for landscape-level conservation management to be implemented to prevent their continuing decline and ultimate extinction.