Endangered butterfly does well on Warton Crag

Highest count for nearly 20 years

November 2010: The number of endangered high brown fritillary butterflies has significantly increased this year at Lancashire Wildlife Trust's Warton Crag Nature Reserve, with surveys showing the highest count for nearly 20 years.

CONSERVATION SUCCESS: The high brown fritillary

The high brown fritillary is of great conservation concern in the UK, having declined more rapidly than any other butterfly species in recent decades. It has disappeared from many of our woodlands, where suitable habitat has been lost through development or the ending of traditional management practices.

It is now found only at a small number of sites in the country, most of which are in the limestone areas around Morecambe Bay.

Warton Crag nature reserve is an area of open limestone woodland that is extremely important for threatened butterfly and moth species, with many - such as the pearl-bordered fritillary and barred tooth-striped moth, as well as high brown fritillary - identified as priorities for conservation under the UK Biodiversity Action Plan.

Complex life cycle

The caterpillars of high brown fritillary hatch in early spring and feed on violets, before pupating to emerge as adult butterflies in June and July. These butterflies are only on the wing for a few weeks each year and so habitat must be right to allow nectaring, mating and egg-laying in this short time.

The management work undertaken by the trust over the past three years has been funded by Lancashire Environmental Fund. This work aims to establish the right mix of woodland and scrub, bracken and flower-rich grassland to benefit high brown fritillaries at each stage of their complex lifecycle.

To help assess the effectiveness of habitat management work, weekly surveys for high brown fritillary are carried out as part of an annual programme of butterfly monitoring on Warton Crag, involving Trust staff and volunteers.

North Lancashire Reserves Officer Reuben Neville said: ‘This is fantastic news and we're hoping that the significant increase in High Brown Fritillary numbers recorded in 2010 is an indicator of better times ahead for this beautiful butterfly.'

In the meantime, Lancashire Wildlife Trust will continue with habitat management work and monitoring to help safeguard Warton Crag as a hugely important site for butterfly and moth conservation.