This article is more than 2 years old

This article is more than 2 years old



The combination of a harsh winter and sunny May and June has given the population of the UK’s most endangered butterfly, the high brown fritillary, a welcome boost.

Volunteers have been counting rare butterflies in a wooded valley on the Devon coast, which has been the focus of a project to encourage species such as the high brown fritillary.

Matthew Oates, a National Trust volunteer and one of the UK’s leading butterfly experts, said: “The butterfly seems to be having a very good year, with over 200 seen during the count.

“Ideal weather conditions; a cold and harsh winter, which has helped knock back the bracken and then a warm and sunny May and June have been ideal for caterpillar development.

“As we are having some fairly dry weather, it’s now the perfect time for seeing this large and powerful butterfly.”

Conservationists believe changes to woodland management, such as the abandonment of coppicing, have contributed to the steep decline of the large, fast-flying butterfly over the past 50 years.

The National Trust has been given £100,000 by the People’s Postcode Lottery to improve 60 hectares (150 acres) of lowland heath and wood pasture at Heddon Valley in north Devon as a habitat for the butterfly.

Other butterflies including the heath fritillary, as well as birds such as the nightjar and Dartford warbler, are also expected to benefit.

To make Heddon Valley more butterfly friendly, pathways have been cut through the bracken using a remote-controlled flailing machine to allow them to move through the landscape.

The high brown fritillary (argynnis adippe) is usually seen flying over bracken and low vegetation in woodland clearings or resting on flowers such as thistle and bramble. The butterfly has orange and black wings and distinctive ringed “pearls” on the underside of its hindwings.

It was once widespread in England and Wales but since the 1950s has suffered a dramatic decline and is only found at about 50 sites. In addition to Exmoor, other sites include Dartmoor in Devon and outcrops of limestone at Morecambe Bay.

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High brown fritillaries overwinter as eggs, which are laid singly on leaf litter on dog violets or among moss growing on limestone outcrops.

The larvae hatch in early spring and spend long periods basking on dead bracken or in short, sparse vegetation.

The temperatures in these microhabitats can be 15-20C higher than in surrounding grassy vegetation, allowing the larvae to develop quickly even in cool spring weather. The larvae have feathered brown spines, giving them the appearance of dead bracken fronds.

A charity warned last week that Britain’s biggest butterfly, the swallowtail, could become extinct within four decades because of rising sea levels.

The Swallowtail and Birdwing Butterfly Trust called for new inland habitat to be created for the swallowtail because much of its home, the Norfolk Broads, are predicted to turn into salt marshes later this century.