The Heath Fritillary in the Blean Woodland Complex

Targeted management as a result of continued monitoring work have helped Heath Fritillary numbers in the Blean Woodland Complex recover to pre-1980 levels. 

The Heath Fritillary is one of Britain’s most threatened butterfly species, having undergone population declines of 73% between 1984 and 2004.  The Blean Woodland complex in Kent is now a major stronghold for the species and contains approximately 60% of all UK colonies. 

In the Blean Woodlands the Heath Fritillary uses sunny clearings such as; coppice coupes or recently clear-felled woodland where its larval foodplant, Common Cow-wheat Melampyrum pratense, is abundant in sparse vegetation; these clearings should be connected by wide, sunny rides.  The butterfly was locally known as ‘Woodman’s Follower’ as it followed the traditional coppice cycle.

The Heath Fritillary occupies areas which remain suitable only for short periods of time, it reaches maximum population size in the first two or three years after management then populations decline as conditions become too shady. Without regular management Heath Fritillary colonies can be lost, there was a rapid loss of colonies in the early 1990s (with just 14 colonies and 19 ha occupied in 1989).

Butterfly Conservation has been monitoring all known Heath Fritillary sites in the Blean Woodlands since 1980 and since 2002 has co-ordinated all the survey results, mapping management areas and the occupied habitats.  All management work in the Blean is under-taken by the woodland owners, principally the RSPB, Forestry Commission and Kent Wildlife Trust.

Project Aim

The aim of the project was to recover Heath Fritillary numbers to 1980 levels (25 colonies), with a target of achieving 30 ha of suitable occupied habitat each year. To maintain populations in such a dynamic landscape suitable clearings must be created (and colonised) at the same rate at which colonies are being lost.

Methods

• Monitoring data was used to target management close to existing colonies.

• Management included the creation of clearings such as coppice coupes (greater than 0.2 ha) and clear-fell areas.

• The clearings should be connected by wide, sunny rides; these rides can be managed by wide ride cutting, ride-widening/creating scallops and managing way-leaves.

• Using timed-counts and habitat suitability assessments continue to monitor occupied sites, sites of new management and unoccupied management blocks from the past two years. Monitoring will assess the success of management and continue targeting future management. 

Results

• 136.7 ha of management was conducted by woodland owners between 2008-2011, including clear-felling, ride management and coppicing.

• Area occupied in 2011 was nearly back up to 1980 levels, with 28 ha occupied.

• The total number of colonies in 2011 (23 colonies) was similar to 1980 levels (25 colonies), with fewer fragmented small colonies and an increased number of colonies occupying a larger area.

• In Thornden Woods (within the Blean woodlands) there was a change in the occupancy of cut coppice from 18% in the early 1990s (without targeting) to 75% by the late 1990s (by targeting with monitoring data).

Success!

Following a rapid loss of colonies from the Blean Woodlands in the 1990s numbers have now recovered to pre-1980 levels, this is largely due to the targeted management as a result of continued monitoring. The project demonstrates the importance that monitoring data plays in successfully targeting management for a highly dynamic species.  The monitoring data also keeps managers and landowners informed and focused on priorities.  The cost of adding this species element to the conservation of the woodlands is only about 3% of the overall budget and it adds huge value to the overall conservation effort. 

Funders

Natural England as part of the Species Recovery Programme and Butterfly Conservation Members and Donors

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