Marsh Fritillaries and Dukes

Lambourn, near the Berkshire-Oxfordshire border, is a hotspot for several rare butterflies. The keen naturalist can still record some seldom-seen blues, fritillaries and skippers in the surrounding countryside known as the Berkshire Downs.

Marsh Fritillary (underside)Two butterflies in particular – Marsh Fritillary and Duke of Burgundy – have their last local breeding colonies in this area. Nowhere else in Berkshire seems to host these threatened butterflies any more. Moreover, the last sites are tiny fields, very vulnerable to change.

Special conservation projects are underway to help the Dukes and the Marsh Frits… but will they achieve results before Berkshire becomes bereft of them?

The hills have eyes

The race is on to beat the threat of extinction, so it is important to know if extra sites have recently appeared (or old colonies reappeared). Next time you’re in the Berkshire Downs, look out for Duke of Burgundy and Marsh Fritillary. If you have seen these butterflies in the Berkshire Downs, I’d like to know.

Photos – the rarest butterflies in Berkshire

Marsh Fritillary (upper side)
Marsh Fritillary (upper side)
Marsh Fritillary (underside)
Marsh Fritillary (underside)
Duke of Burgundy (upper side, male)

Duke of Burgundy (upper side)

Duke of Burgundy (underside, female)

Duke of Burgundy (underside)

Why are they disappearing?

The rolling landscape of chalk downland was once covered in age-old pasture, with an ancestry dating back to the last Ice Age. These noble, ancient grasslands are extremely rich in their variety of life and are just as vital to British biodiversity as any ancient woodland, the habitat many people consider to be a ‘climax’ of nature.

Marsh Frits and Dukes each evolved to fit a tight ‘niche’ in the ecosystem, living in a way no other creature does. That means they don’t compete with similar species, in the way that, for instance, Great Tit and Blue Tit compete for food. On the flipside, the specialist survival strategy means these butterflies are ‘living on the edge’. Each thrives only where its caterpillar food plant flourishes, and that limits where they can exist.

Marsh Fritillary larvae lunch on Devilsbit Scabious (Succisa pratensis) which grows abundantly when grazing and soil conditions are a particular combination. Duke of Burgundy caterpillars eat Primula (cowslip or primrose) whose leaves dry out too soon if not shaded, but the adults cannot tolerate shade, they need to bask in sunshine. Hence the Dukes are tied to places where primulas have a combination of sunshine and cover, such as young coppiced wood, or grassland being invaded by scrub.

For ages the ancient pasture of the Berkshire Downs lay across vast areas, interwoven with small crop fields and coppiced ancient woods. Despite the landscape’s constant flux under the influence of humans and grazing animals, the Duke and Fritillary had many places to live within a distance they could fly. In fact, the sustainable rate at which humans managed the countryside was vital to the survival of many species which adapted to use different stages of change.

There were once plenty of places where conditions were just right. Today there are fewer good spots and they tend to be further apart! Modern agriculture has destroyed and divided ancient grassland, and now the remaining fragments are often isolated and small. Woodlands are not coppiced as often nowadays, if at all.

What can be done?

Landowners, farmers and foresters are the key, because they manage the countryside. Commonly the landscape around Lambourn is dominated by large crop fields, and there are also large pockets of land dedicated to horses (“Lambourn, Valley of the Racehorse“). Money to pay for wildlife projects is available to land managers, and projects could include butterfly-saving schemes.

Many farmers, understandably, are cautious of the terms linked to grant schemes. But these can be highly agreeable contracts, especially for the more difficult areas of ground on a holding.

I am involved with large-scale butterfly conservation projects for two landowners near Lambourn, who certainly did not turn land over to Environmental Stewardship for the feelgood factor alone. Their agents were astute in making sure the grant aid was definitely worth the effort and maintenance. With careful consideration, and a positive attitude to possibilities, we developed very good schemes to suit the business interests and the top local wildlife targets.

Please contact me if

  • you see these butterflies   – or –
  • you’re an interested landowner or farmer

Enquiries will be treated confidentially.

Jason Ball @ Natureheads.com – 07719 225965

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