1. Habitat Management for Boloria euphrosyne at its Last Site in North East Wales – A Case Study
Jan Miller, Butterfly Conservation Volunteer,
Eyarth Rocks Reserve
Eyarth Rocks has been a Butterfly Conservation reserve since Its 9 ha supports a rich variety of butterflies and is the last stronghold in North East Wales of the Pearl-bordered Fritillary (Boloria euphrosyne).
B. euphrosyne is a woodland edge species requiring freshly cleared areas to breed. On this east-facing, thin-soiled, limestone pavement, the larvae need a balance between the sole larval foodplant Viola riviniana and shade and shelter from bracken (Pteridium sp.)
Boloria euphrosyne
Scrub & bracken in 2000 before work started
Restoring Habitat
The first task was to clear overgrown areas to allow Viola riviniana to regrow. The habitat management plan was to clear approximately 1 ha each winter leaving shelter belts.
Chain-saw contractors were used to cut down trees, and volunteers to clear and burn felled timber and scrub. About 6 volunteers from a pool of 20 worked 2 days a week between November and March.
The maximum population count of B. euphrosyne increased from 5 individuals in 2000 to 98 in 2006. 40
Cleared area with shelter belts
Some of our volunteers
Management work starts on reserve
Maximum Counts of Boloria euphrosyne at Eyarth Rocks
Testing different Management Methods
Cleared areas must be kept attractive to egg-laying females. Scrub is controlled by limited sheep grazing in August. To maintain the balance between pteridium and viola three methods were tested:
1. not cutting pteridium;
initial strong growth of viola after clearing scrub, but pteridium grows back strongly and dominates
2. cutting pteridium once a year and allowing re-growth in summer;
enough light for new violets to grow early in the year and shade to protect them later in the summer.
3. cutting pteridium twice a year and raking the ground clear.
violets dry out and die later in the summer
The results were monitored with biannual fixed quadrats and percentage cover of plant species. The percentage cover of viola was 40% with treatment 2 compared to 10% and 5% with treatments 1 and 3 respectively.
V. riviniana regrowth shaded by Pteridium
Pteridium Cut Once a Year
Conclusions
Areas where Pteridium regularly cut and raked off encourages growth of grass and decrease in violets.
Balance between Pteridium and viola is crucial - Too much Pteridium litter = no Viola
- Too little new Pteridium growth = dries out in summer =no Viola
Cutting once a year in early summer encourages most Viola.
Rabbit damage appears to create seedbeds for Viola; this could be worth further study