Nature Features

A survey of pearl-bordered and small pearl-bordered fritillary butterflies at a Devon nature reserve has revealed that numbers have increased dramatically during the past 20 years.

The butterflies are thriving at the Devon Wildlife Trust's Marsland nature reserve on the North Devon coast.

The survey has taken place over two decades, during which the habitat has been carefully managed for the benefit of the butterflies.

The work is clearly paying dividends, and the species are flocking to the reserve in stark contrast to the national picture, where their numbers are in decline. 

Marsland nature reserve (Andrew Taylor)

The trust's nature reserves officer Gary Pilkington has been managing the wooded valley's glades at Marsland for over 20 years.

He said: "We have worked hard over the last two decades to improve the habitat for these beautiful and rare insects and it is great to see such positive improvements compared to the over 50% decline nationally for both the species.

"Over the years we have learnt exactly what they need to thrive here including appropriate bracken control, scrub management and providing the open ground loved by the pearl-bordered fritillaries.

"This is the ideal time of the year to see small pearl-bordered fritillaries in flight so our next job this month (May 2008) will be to monitor their numbers."

At the height of their numbers, in 2003, there were 288 pearl-bordered fritillary butterflies at Marsland. The peak for the small pearl-bordered fritillary was in 2005, when 106 were counted.

A butterfly enjoying the Marsland habitat

The management work - carried out by DWT staff, local contractors and volunteers - has helped to remove gorse, willow, alder and other scrub in the habitats best suited to the butterflies.

The work has seen large increases in the numbers of common dog-violets which is the food plant of the fritillaries' caterpillars, as well as bugle which is the main nectar source for the adults. 

The 212-hectare reserve is home to five species of fritillaries - and they have different needs.

Gary said: "The small pearl-bordered fritillary thrives in the damper sections of the woodland, whilst the pearl-bordered fritillary enjoys the sunny west-facing slopes.

"Even though we are doing well, the work still has to continue each year, it' a constant battle. One of the other fritillaries, the high brown, is only just hanging on here so we certainly can't rest on our laurels."