Stockbridge Down

Stockbridge Down in May.

David Beeson, with butterflies by John Solomon.

 A butterfly walk that is best followed in the early afternoon.

North-west Hampshire’s geology is dominated by chalk.

Chalk is a soft, white, porous, sedimentary form of calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of the minute shells shed from micro-organisms. The rock is porous, soluble and alkaline in nature. As it is laid down in shallow seas it will also contain other sediments, such as clay. When rain dissolves away the calcium carbonate the clay is left behind and forms the clay cappings, with oak trees, so common on local hill tops.

Open, often sheep grazed, hills and pastures are called ‘downs’. Most of the shallower slopes have been ploughed for cereal growing. However, a remnant of the Hampshire downlands is owned and maintained by the National Trust – Stockbridge Down.

This exploration of this fragment of the once extensive Hampshire and Wiltshire downlands starts from the lower carpark, on the Winchester end of the land.

The area is described by the National Trust: ‘Discover breathtaking views and spot a variety of wildlife at Stockbridge Down on the Mottisfont estate. (It is) a chalk hill supporting grassland, areas of scrub and partially wooded margins, the habitat diversity of Stockbridge Down is hugely beneficial to local wildlife. (It possesses) the remains of an Iron Age hill fort, earthworks and around 14 Bronze Age burial mounds. This is a site of importance for archaeology, as well as nature conservation.’

Active management occurs in keeping a balance of trees, scrub and open chalky pasture.

The route you follow is not critical, but this clockwise walk will enable you to pick out areas in which you are likely to encounter particular species of, especially, butterflies – of which you could encounter thirty species over a year.

Just beyond the entrance gateway with its explanation board, one encounters the ubiquitous stinging nettles. Why here? The plant enjoys a nigh nitrogen input from human and canine urine, so grows especially strongly.

The chemistry of stinging nettles.

The easily broken, hollow stinging hairs (trichomes) that line the edges of the leaves act as needles and readily piece human skin. The chemicals they contain cause tingling, inflammation and pain that can last for several hours. An effective deterrent to pickers.

The hollow nettles are filled with two ingredient types: acids and neurotransmitters. The latter cause the inflammation (antihistamines should sort that out), while formic, tartaric and oxalic acids cause the pain. There is no scientific evidence that rubbing the area with dock leaves has any effect in reducing the pain.

The oak and blackthorn plants have a covering of lichens. These grey-green masses are a combination of algae and fungi in an inseparable mixture. Crusty, leafy and shrubby types can be encountered, with the last type usually associated with sulphur dioxide-free air. (The yellow-orange encrustation frequently seen on house roofs is a lichen called Xanthoria. It is stimulated into growth by bird droppings.)

Lichens

Early May is the oak’s breeding time. Small, pollen-laden catkins hang down from the new shoots, while at the end of other twigs are the minute red female flowers. The require some looking for! The light, yellow pollen grains are carried on the wind to the female flowers, so the plant is not associated with the buzz of bees.

Oak catkins

At this stage of the year, the oak trees are employing all their reserves into leaf growth. The plant needs the leaves to commence their photosynthesis as soon as possible. Because of this the leaves are unfilled with their ‘expensive’ chemical protection – tannic acid. This is produced mainly when the leaves are mature. Hence the young leaves are open to being eaten by the myriads of miniscule caterpillars that hatch now from the pinprick-sized eggs laid last year. Overwinter the tits have been seeking out the eggs for food, now they require the larvae for baby food. A poor caterpillar year equals a poor tit breeding year.

[https://www.gla.ac.uk/news/archiveofnews/2017/july/headline_536578_en.html] For information on urban tits.

This part of the reserve, with a patchwork of shrubs and open glades, has the correct environmental conditions for comma and peacock butterflies. Coppiced hazel is common and at ground level blue flowers seem to predominate – speedwell, forget-me-nots and the beautiful ground ivy. Later in the year the common bramble (blackberry) found here will be a rich food source with its flowers and juice-packed fruit. The plant is the food source for several dozen species of moth larvae, so, despite its aggressive habit, it is a valuable plant for natural ecology.

Peacock

Turning slightly left at the twin silver birches the chalky bedrock shows clearly on the pathway and by the burrowing of rabbits. Here there is more open scrub, and that variant of the dowland encourages other butterfly species.

Even on the dull day of my visit, dingy and grizzled skippers were present, although the coolness kept them comatose. Bird’s-foot-trefoil leaves supply the caterpillars with one of their food sources.

Female, grizzled skipper
Dingy skipper

Small copper butterflies were about in numbers and far more active than the skippers. Males are territorial, often choosing a piece of bare ground or a stone on which to bask and await passing females. They behave aggressively towards any passing insects, returning to the same spot when the chase is over. Sorrel is the larval food plant and there can be several ‘flushes’ of adults during a season.

Small copper

(See the Butterfly Conservation web site for more details on all species. https://butterfly-conservation.org)

Small copper

The other butterflies frequently seen over Stockbridge Down in May are the orange-tip and yellow brimstones.

Ant hills are becoming more obvious now. The Yellow Meadow Ant is familiar to us as the ant that creates anthills in grassland and downland habitats, but also appears in our gardens if the grass is not cut too often. They build a soil dome above the nest (which can extend a metre below the ground) to help regulate temperature and humidity. The Yellow Meadow Ant is social and forms colonies; the workers are mainly active underground and not often seen unless the nest is disturbed by, for example, green woodpeckers or rabbits.

Observe the vegetation on a mature hill – for it is often quite distinct from that nearby. Rabbit droppings, left on the site, are common and they add nutrients that encourages different plants to establish themselves.

With the surrounding area opening out beyond the white-leaved whitebeam tree there is a rich ground flora.  The vegetation is a stark contrast to the bare ground under the trees and dense shrubs. Beneath your feet will be aromatic marjoram, wild strawberries with their glowing white flowers, ground ivy with its pungent foliage, statuesque bugle and bright blue-flowered speedwells. The natural plant diversity is high on chalky soils – a stark contrast to what is found on heathlands.

Ground ivy

Various paths lead leftwards towards the old racing gallops (in the C19 there were race courses at Danebury and on the northern edge of Harewood) that run parallel to the road. Once there, my advice is to turn back (left) towards the parking spot. Along this route, on a fine May day, the skippers and other species (including green hairstreaks) will be around in abundance.

Conservation activities have opened the land between the path and the road and this has caused a burst in a rich ground flora. You’ll spot: burdock with its annoyingly adhesive seed heads, insect-friendly viper’s bugloss, creeping buttercup, St John’s wort and many other species. All of these will have their animal ‘partners’ – be that larvae that eat their leaves, butterflies feeding of their sugar-rich nectar or ground-nesting solitary bees taking both pollen and nectar. Voles, mice and shrews will feed here too. 

This location is usually especially populated with lepidoptera and deserves plenty of attention.

It is possible that you may have noticed male (yellow-coloured) and female (essential white-coloured) brimstone butterflies. Some think that it is the colour of the males that generated the common name of this delightful insect – the colour of butter!

Male, brimstone.
Brimstone

Having enjoyed the butterfly high spot of this mid-May exploration, perhaps it is time to resume the routeway westwards and up the slope, soon passing a semi-enclosed burial site of possible hangings (execution cemetery).

https://hampshirearchaeology.wordpress.com/2015/11/16/buried-in-time-an-execution-cemetery-on-stockbridge-down/

The downland is more open here, and less suitable for the butterflies already encountered, so, enjoy the views and vegetation.

When given options follow your selected pathway towards the right and you’ll encounter the Iron Age fort – Woolbury Ring. With the earthworks providing steep slopes and soil-rich bottoms the edges of the ring has a stimulating vegetation pattern that provides hosting for many butterflies. Rockroses, a magnet for early-day bees, and cowslips are common here. Look out for small heath butterflies and the amazing colour of the small copper butterfly whose larvae usually feed on sorrel leaves.

Small heath
Small heath

With the slopes facing the sun in the afternoon the area seems to attract insects.

The pathway leads us slowly down a gentle slope, through shaded areas and open chalky meadows and eventually back to the starting point.

Weather conditions earlier in the year, the previous year and around the time of your own visit influence butterfly numbers and diversity – so select your visit date carefully and try again in a few weeks’ time – you may well encounter new species.

Female, brimstone.

https://www.nationaltrust.org.uk/mottisfont/features/butterflies-at-stockbridge-down

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