The Heath Fritillary (Mellicta athalia) on Exmoor: Changing Status 1980-2000 and Conservation

Recommendations

Butterfly Conservation Report No. S01-30

Katherine Stewart, Nigel Bourn, Martin Warren and Tom

Brereton.

May 2001

Master Copy - Butterfly Conservation Office, Wareham

National Trust - Cirencester Office, Holnicote Office

English Nature - Taunton Office, Exeter Office, Head Office

MAFF & FRCA - Taunton Office, Exeter Office, London Office

Exmoor National Park

Dartmoor National Park

Butterfly Conservation Branches - Devon and Somerset

South-West Fritillary Action Group (SWFAG) members

Exmoor Natural History Society (ENHS)

Tenants/farmers consulted during the survey

Wessex Water - Bath Office

RSPB - Exeter Office

Environment Agency - Exeter Office, Bridgwater Office

Wildlife Trusts - Devon & Somerset

CONTENTS

TABLES AND FIGURES

EXECUTIVE SUMMARY

1.0 INTRODUCTION

1 . 1 BACKGROUND 1 .2 ECOLOGICAL REQUIREMENTS OF THE HEATH FRITILLARY ON EXMOOR. 1.3 SURVEY HISTORY AND DISTRIBUTION 1.4 LAND ENHANCEMENT SCHEMES RELEVANT TO THE CONSERVATION OF THE HEATH FRITILLARY-THE EXMOOR ESA 1.5 AIMS OF CURRENT STUDY IN 2000

2.0 METHODS

2.1 TIMED COUNT SURVEYS AND POPULATION ESTIMATES 2.2 HABITAT ASSESSMENT 2.3 HISTORICAL POPULATION DATA AND MANAGEMENT INFORMATION

3.0 RESULTS

3.1 NUMBER OF SITES, DISTRIBUTION AND POPULATION SIZES IN 1999/2000 3.3 COMPARISON BETWEEN THE 1989 AND 2000 SURVEYS 3.4 CHANGES IN POPULATION SIZES FROM 1984 TO 2000

3.4.1. Collated Index from all Heath Fritillary sites on Exmoor 3.4.2 Fate of 1989 sites with respect to site size 3.4.3 Effect of Isolation and Area of Sites on Population Persistence

3.5 CHANGE IN VEGETATION STRUCTURE 3.6 MANAGEMENT HISTORY ON EXMOOR

3.6.1 Grazing regimes on Heath Fritillary sites 3.6.2 Changes in the burning regime on Heath Fritillary sites 3.6.3 Management agreements on Heath Fritillary sites 3.6.4 Impact of Deer Activity 3.6.5 Case Studies of Exmoor Heath Fritillary Sites and Overview of Management Changes

4.0 DISCUSSION

4.1 POPULATION RESULTS 4.2 THE IMPLICATIONS OF METAPOPULATION DYNAMICS FOR HEATH FRITILLARY CONSERVATION 4.3 MANAGEMENT CHANGES 4.4 EXAMPLES OF OTHER PRIORITY INVERTEBRATES THAT DEPEND ON EXTENSIVE GRAZING -IMPLICATIONS FOR THE ESA SCHEME 4.5 FULFILLING SAP OBJECTIVES AND CONTRIBUTING TO THE EXMOOR BAP 4.6 FUTURE RESEARCH AND MONITORING 4.7 GENERAL RECOMMENDATIONS

5.0 ACKNOWLEDGEMENTS

6.0 REFERENCES

7.0 APPENDICES

7.1 APPENDIX ONE - HEATH FRITILLARY POPULATION AND VISIT DATA 7.2 APPENDIX Two - TRANSECT DATA FROM BIN COMBE AND HALSE COMBE 7.3 APPENDIX THREE - AREA AND ISOLATION DATA USED IN THE STATISTICAL TESTS 7.4 APPENDIX FOUR - POPULATION ESTIMATE DATA 1984-2000 FOR ALL SITES 7.5 APPENDIX FIVE - VEGETATION DATA 7.6 APPENDIX Six- MANAGEMENT DATA 7.7 APPENDIX SEVEN- QUESTIONS ASKED TO FARMERS/LANDOWNERS DURING THE MANAGEMENT SURVEY 7.8 APPENDIX EIGHT - CASE STUDIES OF EXMOOR HEATH FRITILLARY SITES 7.9 APPENDIX NINE - PRIORITY BUTTERFLIES AND MOORLAND MANAGEMENT ON EXMOOR AND DARTMOOR

TABLES AND FIGURES

TABLES TABLE 1.1: EXMOORESA TIERS AND PAYMENT LEVELS

TABLE 2.1: SIZE CATEGORIES FOR POPULATION ESTIMATES

TABLE 2.2: COW-WHEAT ABUNDANCE SCALE

TABLE 3.1: ESTIMATED POPULATION SIZES IN 1999/2000

TABLE 3.2: UNOCCUPIED SITES IN 1999/2000 TABLE 3.3: SIZE POPULATION CATEGORIES IN 1989 AND 2000

TABLE 3.4: FATE OF 1989 SITES IN 2000 WITH RESPECT TO EXTINCTION AND PERSISTENCE TABLE 3.5: MANN-WHITNEY TEST RESULTS COMPARING EFFECTS OF ISOLATION AND AREA ON OCCUPIED AND EXTINCT HEATH

FRITILLARY SITES ON EXMOOR 1989-2000

TABLE 3.6: COMPARISON IN VEGETATION DATA BETWEEN 1989 AND 2000

TABLE 3.7: COMPARISON BETWEEN OCCUPIED AND UNOCCUPIED SITE VEGETATION DATA

BETWEEN 1989 AND 2000

TABLE 3.8: OVERALL CHANGES IN GRAZING FOLLOWING THE INTRODUCTION OF THE EXMOOR ESA ON THE 8 STUDY SITES

TABLE 3.9: FREQUENCY OF BURNING ON HEATH FRITILLARY SITES (LISTED IN DECREASING ORDER OF

POPULATION SIZE) TABLE 3.10: SUMMARY TABLE SHOWING SITES ENTERED INTO MANAGEMENT AGREEMENTS

TABLE 3.11 SUMMARY OF HABITAT AND MANAGEMENT ON CASE STUDY SITES

FIGURES

FIGURE 3.1: MAP SHOWING THE STATUS OF HEATH FRITILLARY COLONIES IN (A) 2000 AND (B) 1989

FIGURE 3.2: COLLATED INDEX GRAPH, 1984-2000

FIGURE 3.3: THE EFFECT OF ISOLATION AND SITE AREA ON THE OCCUPANCY OF HEATH

FRITILLARY COLONIES IN 2000

FIGURE 3.4: THE EFFECT OF ISOLATION AND SITE AREA ON THE OCCUPANCY OF HEATH

FRITILLARY COLONIES IN 1989

EXECUTIVE SUMMARY The Heath Fritillary (Mellicta athalid) is a species of high conservation importance: it is listed on Schedule 5 of the 1981 Wildlife and Countryside Act and is identified as a priority species in the UK Government's Biodiversity Action Plan (BAP) (DOE, 1995). Exmoor is a major stronghold for the species containing over half of all UK colonies in 1989.

The principle aim of this study was to determine possible reasons for the recent decline of the Heath Fritillary on Exmoor, including changing habitat management and the metapopulation status of the species. A management survey was undertaken in autumn 2000 and the colony distribution data was analysed in terms of standard 'metapopulation' variables; the size and isolation of sites.

The results show that the Heath Fritillary has declined by almost 50% on Exmoor since 1989, from 29 colonies to 15 in 1999/2000. The size of many colonies has also decreased, with the number of large colonies declining from 17 in 1989 to 5 in 2000.

A collated index (based on timed counts of adults) calculated from 1984 to 2000 showed a decline in overall population size on Exmoor of 85%.

Between 1989 and 2000 significant vegetation changes were noted. The vegetation height and the percentage bracken cover have both increased significantly, while the percentage cover of bilberry has decreased.

The level of grazing has decreased on many Heath Fritillary sites, with a cessation of winter grazing on half of eight study sites where management details could be retrieved. There is seldom shepherding of stock and many combes have little keep to encourage animals to stay and graze, exacerbating the problems associated with a reduction in stock density.

A conflict has been identified within the ESA, where a prime aim has been to improve heather quality by reducing grazing pressure. However this reduction appears to be leading to a severe decline in the quality of habitat in the combes for the Heath Fritillary and other threatened invertebrates.

It is thus vital that methods are developed to allow appropriate grazing intensities to be maintained in these combes without compromising heather quality on the higher land. One mechanism recommended is to allow derogations to increase (or maintain) grazing levels on known or potential Heath Fritillary sites.

To enable targeted management it is essential that information about the location and requirements of these threatened invertebrates are made known to the MAFF Project Officers responsible for adminstering the ESA scheme.

There appears to be a strong correlation between regular burning and the size and persistence of Heath Fritillary populations. A more regular burning programme needs to be instigated on Heath Fritillary sites in conjunction with scrub removal, to eliminate some of the build-up in vegetation biomass that makes habitat unsuitable for breeding.

The pattern of occupancy and extinction on individual sites shows that occupancy in 2000 appears to be determined, at least in part, by the size and isolation of a site. Extinctions have been more frequent on smaller, more isolated sites.

The pattern of isolation and area of sites in 1989 and 2000 demonstrates that levels of isolation are increasing as sites are lost. This increased isolation then reduces the rates that a relatively immobile species like the Heath Fritillary can re-colonise former sites or colonise new habitats. Thus the Heath Fritillary on Exmoor is in an even more perilous condition than the loss of 50% of sites implies, as the metapopulations (comprising groups of nearby populations) break down and extinction rates escalate.

The conservation of the Heath Fritillary needs to be considered from a broad landscape perspective, where metapopulation dynamics can be accomodated. Suitable management needs to be carried out in existing and potential habitats over a wide area, allowing populations to build up and naturally colonise new sites.

Butterfly Conservation is collaborating with the National Trust on burning experiments and discussing the practicalities of increasing grazing/burning with MAFF and landowners.

Continued detailed surveys are essential to determine responses of colonies to management and to monitor metapopulation dynamics.

It is important that at least one transect is recorded each year for the duration of the Heath Fritillary flight period, according to the standard criteria. This allows the timed count data to be adjusted to peak flight period and population levels to be assessed accurately.

More research needs to be undertaken into the impact of livestock and deer grazing on Heath Fritillary sites.

1.0 INTRODUCTION

1 .1 Background

The Heath Fritillary (Mellicta athalid) is a species of high conservation importance: it is listed on Schedule 5 of the 1981 Wildlife and Countryside Act and is identified as a priority species in the UK Government's Biodiversity Action Plan (BAP) (DOE. 1995).

A study by Butterfly Conservation in 1999 showed that the Heath Fritillary had declined by almost 50% on Exmoor in the 10 years since the last thorough survey (Feber et a/., 2000). The number of known colonies on Exmoor had declined from 29 in 1989 to only 15 in 1999. Bad weather has hindered recent surveys and a thorough re-survey of all the past known sites was undertaken in June/July 2000.

The principle aim of this study was to determine possible reasons for the decline, including changing habitat management and the break-up of metapopulations1 (natural extinctions exceeding colonisations). A management survey was undertaken in autumn 2000 and the colony distribution data was analysed in terms of standard 'metapopulation' variables, the size and isolation of sites.

1.2 Ecological Requirements of the Heath Fritillary on Exmoor

On Exmoor, the Heath Fritillary thrives in short heathy habitats when the larval foodplant, cow-wheat (Melampyrum pratense) grows amongst bilberry (Vaccinium myrtilhis). The sheltered heathland with scattered common cow-wheat is NVC community HI 2, Upland Heath. Heather (Calluna vulgar is) and bilberry dominate the vegetation with locally abundant bracken (Pteridium aquilinum). Sites usually lie between 200m to 400m in altitude (Barnett and Warren, 1995). These sheltered heathland combes occur in the transition zone between upland and lowland heath and need to be actively managed. A lack of management can lead to a loss of open areas with scrub encroachment and denser vegetation causing a decline in habitat quality for the Heath Fritillary. Management needs to be undertaken through appropriate burning or grazing regimes, with cattle and pony grazing especially valuable for breaking up dense bracken stands and helping to maintain open areas of bilberry and cow-wheat.

The primary larval food plant on Exmoor is cow-wheat but an occasional secondary foodplant is foxglove (Digitalis purpurea) (Warren, 1985). The larvae emerge from hibernation in March/April and feed when the weather is warm. This is thought to be a crucial period with high mortality; especially during a cold spring which slows larval development.

1 A metapopulation is a collection of local populations connected by occasional dispersal, in which there are local colonisations and extinctions (Gilpin and Hanski, 1991).

1.3 Survey History and Distribution

In 1980, the Joint Committee for the Conservation of British Insects coordinated a thorough survey of all Heath Fritillary colonies in the UK (Warren et al, 1981). That survey found only one Heath Fritillary site on Exmoor. Since 1980 a further 28 colonies had been found by 1989 (Warren, 1989). However it is not known whether these were recently established colonies or simply overlooked.

The total number of Heath Fritillary colonies in the UK is now 40, with two on the Devon/Cornwall border, a re-introduced colony in West Devon, 15 sites on Exmoor, 18 sites in the Blean Wood complex in Kent, and four re-introduced colonies in Essex (Brereton et al., 1998).

The Heath Fritillary sites (occupied and unoccupied in 1999/2000) occur in seven main areas on Exmoor (ENPA, 2001):

1. Alcombe (Alcombe Common, Periton Combe and Grabbist Hill) 2. Porlock Common (Berry Castle and Shillett Combe) 3. Rodhuish (Rodhuish Common) 4. Dunkery (Bin Combe, Hanny Combe, Spangate, Luccombe Plantation,

Hollow Girt, Halse Combe, Rey Combe, Godsend Moor, Horner Hill, Horner Side, Nutscale Reservoir, Lang Combe, Bagley Combe, Sweetworthy, Hollow Combe and Aller Combe)

5. Lillycombe Estate (Metcombe, Lillycombe, Holmers Combe and Weir Wood) 6. Haddon (Haddon Hill) 7. Yealscombe (Yealscombe and Yealscombe Water)

1.4 Land Enhancement Schemes relevant to the Conservation of the Heath Fritillary - the Exmoor ESA

The need for management on sites to prevent succession to scrub and woodland means that there is a potential cost to the site owner. However, in recent years payments for positive management of sites have become available on Exmoor through the Environmentally Sensitive Area (ESA) in 1993 and other schemes such as agreements with Exmoor National Park and English Nature. The ESA covers an area of 80,615ha and covers the whole of the Exmoor National Park (ADAS, 1997). The scheme involves different tiers of payment for farmers for a variety of environmental management prescriptions. The relevant tiers and payments are given in Table 1.1, including the payment ' rates following a review in 2001.

Tier 1 (part 4) is for grassy moorland and has prescriptions that include maintaining the moorland in its present or an improved state. No fertilisers or lime can be added and no poaching, over-grazing or under-grazing is allowed (stocking levels have to be agreed with the Project Officer). Livestock must graze lightly and not be allowed to concentrate in vulnerable areas such as heather margins or recently burnt heather. Supplementary feeding is only permitted with MAFF's approval.

Tier 1 (part 5) is for heather moorland and coastal heath and stipulates that a stocking level of 0.225 livestock units (LU) per hectare must not be exceeded. No winter cattle grazing is allowed. Sheep may be grazed, but not to exceed one ewe per hectare. Tier 2 (part 1) stipulates a summer stocking rate of 0.1 LU and no winter grazing apart from pure-bred Exmoor ponies. This tier is particularly for moorland that is in a "poor" or "suppressed" condition.

The sympathetic management of heather moorland is encouraged through the ESA as these areas are recognised as an important national wildlife resource. Overgrazing, winter feeding and poaching were identified as important factors in the decline of heather quality, and the ESA scheme aims to reverse this sitviation by providing farmers with incentives to undertake appropriate and sustainable management. Integrated moorland management is encouraged through a plan that includes burning, cutting, stock management and scrub/bracken control. It is possible to adapt an ESA agreement to make allowances for a species of particular nature conservation importance, such as the Heath Fritillary. ESA Project Officers need to be aware of the appropriate management requirements for these priority species.

Table 1 . 1 : Exmoor ESA tiers and payment levels

TIER

LAND ELIGIBLE

PAYMENT PER HA

PAYMENT REVIEW 2001

Tier I (part I) all land £14 £16 Tier 1 (part 2)

improved permanent grassland (for existing agreement holders only)

£27

£25

Tier 1 (part 2A) improved permanent grassland £18 £19 Tier 1 (part 2B) low input permanent grassland £30 £31 Tier 1 (part 3) enclosed unimproved permanent grassland £38 £40 Tier 1 (part 4) moorland £34 £34 Tier 1 (part 5) heather moorland and coastal heath £50 £50 Tier 2 (part 1)

heather moorland and coastal heath with lower stocking rates

£60

£60

Tier 2 (part 2) reversion of land to heather moorland £225 £225

1.5 Aims of current study in 2000

• To confirm the precipitous decline indicated in 1999 by repeating a survey of all recorded sites.

• To determine reasons for the decline. • To analyse population data collected on Exmoor over the last 20 years. • To analyse extinctions, population persistence and adult number

fluctuations with respect to landscape management changes. • To make recommendations for Heath Fritillary conservation to enable

this serious decline to be reversed. • To instigate a series of site meetings to aid the introduction of

appropriate management on sites.

2.0 METHODS

2.1 Timed Count Surveys and Population Estimates

Timed count surveys were carried out on Exmoor between 7th June 2000 and 18th July 2000. All of the sites that were visited in 1999 were resurveyed (with the exception of Lang and Holmers Combe) with the help of volunteers and conservation staff at Butterfly Conservation, the National Trust and English Nature. Counts were also carried out periodically along fixed routes (transects) at Bin Combe and Halse Combe by the National Trust.

Timed counts provide a rapid method of monitoring the population size of a colony, and importantly also enable monitoring of the area (ha) occupied by the butterfly (Warren et a!., 1984). The timed count method has been validated for Heath Fritillary by mark-recapture experiments in coppiced habitat in Kent and Cornwall. No more than a single visit is required, as long as this is made close to the predicted peak flight period (determined from local transect data and weather conditions), although three or four visits are ideal.

The number of butterflies seen is recorded in a measured time period of a systematic search of the flight area. The results are used to obtain an estimate of adult density (number of adults per hour x flight area (measured in ha)). Ideally the adult density is multiplied by a correction for the peak flight period (as estimated from the transect data) to give relative adult numbers. This is then used in the equation (y = 0.499x-2.396) where y is the relative adult numbers and x is the estimated population size (Warren, 1985). These population sizes can then be placed into size categories as in Table 2.1.

Unfortunately, not enough individuals were counted on the two butterfly transects in 2000 to enable an annual transect index to be calculated, according to the BMS methodology2. This means that the transect data cannot be used to adjust the timed count data. Several timed counts were undertaken in week 11 (10th - 16th June) for which there is no transect data at all. The population estimates have still been calculated but have not been adjusted according to when they were walked in the flight period. The data used in the calculation can be found in Appendix One (Section 7.1.1).

" The BMS (Butterfly Monitoring Scheme) has strict rules concerning the calculation of » transect annual indices. Each transect walk has to be made in the appropriate weather conditions (above 17°C or 13-17°C with at least 60% sun). A walk has to be undertaken before and after the flight period to enable a curve to be fitted to the weekly data for index calculation. A walk has to be undertaken each BMS week during the flight period, such that Week 1 = 1-7 April, Week 2=8-14 April. Data for one missing week can be calculated as long as there is enough data for the other weeks. There was not enough data collected on the Exmoor Heath Fritillary transects. Only one butterfly was seen at Halse Combe and too few weeks of data were collected at Bin Combe.

Table 2.1 : Size categories for population estimates

SIZE CATEGORY POPULATION ESTIMATE large >250 adults medium 100-250 adults small 10-100 very small <10

2.2 Habitat Assessment

At each site the habitat was assessed using the same method as in the 1999 survey (Feber el al., 2000). The location, size, aspect and slope of the site were recorded. Estimates were made of average vegetation height (cm) using a metre rule, bracken cover (%), dominant vegetation and abundance of cow-wheat. The cow-wheat abundance was measured on a rank scale of 0-5 (Table 2.2), as developed during earlier Heath Fritillary surveys (Warren et a/., 1981). The surveys in 1999 and 2000 collected vegetation data in a similar way to the survey in 1989 to achieve consistency between study periods.

The weather was recorded with an estimate of temperature, wind speed and percentage of sun during the survey. Notes were made of any evidence of site management/condition including indication of deer or stock grazing and burning.

Table 2.2: Cow-wheat abundance scale

SCALE DESCRIPTION 0 absent 1 rare, a few spikes only 2 scarce, a few patches present i j frequent, patches always in view 4 common, ground cover more than 10% 5 abundant, ground cover more than 40%.

2.3 Historical Population Data and Management Information

Analysis of population data on Exmoor was possible over the 20 year recorded history of the Heath Fritillary. This data has mainly been collected by volunteers, with recording in recent years being co-ordinated through the South West Fritillary Action Group (Brereton et al, 1998). There are long runs of data from some Heath Fritillary sites on Exmoor and a collated index was calculated using a method adapted from Pollard (Moss and Pollard, 1993). The collated index is calculated by summing the population estimates for all sites for each year and comparing them to the previous year.

The management data was collected mainly through interviews with the farmers and landowners responsible for land management on the Heath Fritillary sites. Ten people were consulted to cover 15 Heath Fritillary sites. Detailed information was collected from eight of those sites. Examples of the questions asked can be found in Appendix Seven. Conservation staff consulted

included David Lloyd (Exmoor National Park), Nigel Hestor and Paul Camp (National Trust), Majory Taylor (FRCA), Fiona Bowles (Wessex Water) and Flemming Ulf-Hansen (English Nature).

Slides and aerial photos were also examined, in particular the aerial photos held at Exmoor National Park (the whole of the Park is photographed once every four years). Burning records kept by various organisations (e.g. National Trust, Exmoor National Park) were also examined.

3.1 Number of Sites, Distribution and Population Sizes in 1999/2000

The survey in 2000 found colonies at only 14 sites (Table 3.1) confirming the high loss of colonies since 1989 when 29 colonies were located. The past and present distribution of the Heath Fritillary on Exmoor is shown in Figure 3.1. The results show that colonies in the north and west of Exmoor are no longer occupied (e.g. the Lillycombe Estate, Yealscombe and Porlock Common), while those in the south and east have survived better. Full results are given in Appendix One (7.1.2. - Full Visit Data) and Appendix Two (National Trust transect data).

Of the 15 colonies identified in 2000, 5 were large, 1 medium and 9 small. This is an improvement on the size recorded in 1999, especially at Alcombe, Bin Combe, Grabbist Hill, Haddon Hill and Hanny Combe. These were all calculated as medium populations in the 1999 survey but were classified as large in 2000, probably reflecting the better weather during the 2000 flight period. Luccombe Plantation and Periton Combe were also calculated as medium in 1999 but are small populations in 2000. The amount of suitable habitat is declining on both of these sites as succession takes place at Luccombe Plantation and scrub encroachment occurs at Periton Combe. All the other sites have the same population classification in 2000 as in 1999 (see Table 3.1).

Table 3.1: Estimated population sizes in 1999/2000

SITE NAME

GRID REF

ESTIMATED POP SIZE

POP SIZE CATEGORY 2000

POP SIZE CATEGORY 1999

Haddon Hill SS975286 3652 Large Medium Grabbist Hill SS975435 790 Large Medium Alcombe Common - Total* SS9743/4 585 Large Medium Bin Combe SS906410 389 Large Medium Hanny Combe SS913418 356 Large Medium Spangate SS916413 136 Medium Medium Luccombe Plantation SS905444 95 Small Medium Aller Combe SS893425 85 Small Small Luccombe Hill/Hollow Girt SS909437 53 Small Small Sweetworthy SS885424 53 Small Small Hollow Combe SS900429 37 Small Small Periton Combe SS953443 37 Small Medium Halse Combe SS895456 25 Small Small Rey Combe SS895451 11 Small Small Rodhuish Common SS994402 9 not seen in 2000 Small

*All the Alcombe Common sites estimated together as one 'metapopulation'.

3.0 RESULTS

3.2 Unoccupied Sites in 1999/2000

During 1999/2000 surveys failed to locate adults at 14 former sites of the Heath Fritillary (Table 3.2). Lang Combe and Holmers Combe were visited only in 1999 but the other sites were searched thoroughly in both 1999 and 2000 in fine weather when Heath Fritillaries were flying in good numbers at other sites.

Table 3.2: Unoccupied sites in 1999/2000

SITE NAME

GRID REF

DATE SEARCHED IN 2000

NOS SEEN/TIME SEARCHED IN 2000

Bagley Combe SS877424 16/6, 19/6,26/6 0/20, 0/30, 0/80 Berry Castle SSS59449 12/7, 18/7 0/40, 0/40 Godsend Moor SS883413 26/6 0/45 Horner Hill SS902437 26/6 0/35 Horner Side SS898450 during flight period not recorded Lil lycombe SS820467 28/6 not recorded Metcombe SS827467 during flight period not recorded Nutscale Reservoir SS858432 12/7 0/30 Shillett Combe SS860450 28/6, 6/7 not recorded, 0/75 Weir Wood SS828462 during flight period not recorded Yealscombe SS792464 6/7 0/45 Yealscombe Water SS792459 6/7 0/60

3.3 Comparison between the 1989 and 2000 surveys

The maps of the status of the Heath Fritillary in the two survey periods show that there has been a clear reduction in the number of sites, as well as a reduction in population size on those sites that remain occupied in 2000 (Figure 3.1). Since 1989. the number of large colonies has fallen from 17 to 5 and the number of medium colonies from 3 to 1. The number of small colonies has increased from 5 to 9 (see Table 3.3). There have been two new sites found since 1989, Periton Combe and Rodhuish Common.

Thus, as well as a significant loss of colonies, there has also been a reduction in the population size on many sites.

Table 3.3: Size population categories in 1989 and 2000

POPULATION SIZE NUMBER IN 1989 NUMBER IN 2000

large 17 5 medium 3 1 small/very small 5 9 not assessed (but occupied) 4 0 TOTAL 29 15

3.4 Changes in population sizes from 1984 to 2000

3.4.1. Collated Index from all Heath Fritillary sites on Exmoor

The collated index of Heath Fritillary population size shows a build-up from 1984-1990 and then a sharp decline (Figure 3.2). Over the 17 year period there has been a clear downward trend (R2 = 0.54, p= 0.001, n=16). There are also fluctuations that may correlate with weather conditions, although this wras not tested in this report. This decline represents a total reduction in population size of 85% between 1984 and 2000.

Figure 3.2 Collated index graph, 1984

2000 3

3.4.2 Fate of 1989 sites with respect to site size

Table 3.4 shows the status of 1989 sites in 2000, and how many have persisted or become extinct during the 11 year time period. A Chi Squared test was undertaken on the data to see whether the population size in 1989 had any effect on persistence in 2000. The Chi test result was 0.54, which was not significant, indicating that persistence (or conversely extinction) was not affected by the population size in 1989. Large sites are as likely to remain occupied as small ones, and conversely large sites are as likely to have gone extinct in the same period.

Graphs showing population estimates from timed count data for each Heath Fritillary site (1984 - 2000) can be seen in Appendix Four. The graphs are groviped together by their status in 1989, i.e. the first set of graphs are the sites with the six largest population estimates. Those sites are all still occupied, although three of them now support small populations. There is no pattern with the other sites and their persistence or extinction does not appear to be dependent on their status in 1989.

The population estimates have shown a clear downward trend over the 17 year period analysed (see the collated index). Extinctions have occurred regardless of the population sizes in 1989. However, those sites with very large populations in 1989 (>3000 individuals) have fared better with no extinctions, possibly due to the larger size of site.

Table 3.4 Fate of 1989 sites in 2000 with respect to extinction and persistence

1989 2000 Large 4 Medium 1

Persistence

Small 4

9

Large

17

Extinctions 8 Large Medium

Persistence

Small 1

1

Medium

3

Extinctions 2 Large Medium

Persistence

Small 1

1

Small

4

Extinctions 3

3.4.3 Effect of Isolation and Area of Sites on Population Persistence

The Exmoor Heath Fritillary sites were analysed in two groups, one consisting of occupied sites and the other of former sites that have now become extinct. Comparisons were made between occupied and extinct sites with respect to the area of the site (ha) and the isolation (distance to the next nearest site in Ion). The data used can be found in Appendix Three. As the isolation and area data are not normally distributed, the non-parametric Mann-Whitney U-test was used to compare the median of each group (Table 3.5).

The results indicate that the area of the site and the distance from the nearest occupied neighbour were significantly different in the two groups. Occupied sites tend to be larger and nearer to other occupied sites.

To examine this further, a binary logistic regression was undertaken to examine which factors influence the probability that a site is occupied in 2000 (Figure 3.3). The results show that 84.1% of the variation in the response variable (whether a site is occupied or not in 2000) can be explained through the area and isolation factors (p=0.06 and 0.02 respectively. The isolation factor is significant at the 5% level. The plots confirm that occupied sites tend to be much less isolated than extinct ones and are larger, with 8 sites more than 4 ha (value of approximately 0.6 on the log 10 scale). Moreover, no extinct sites had an area greater than 4 ha in 2000. The same pattern of site area and distance to nearest occupied site using just 1989 data is shown in Figure 3.4. The results show that when all sites were occupied in 1989, the majority of sites were near to an occupied neighbour and only two were isolated (Haddon Hill and Grabbist Hill).

Overall the results show that occupancy appears to be determined, at least in part, by the size and isolation of a site. During the study period extinctions have been more frequent on smaller, more isolated sites.

Table 3.5: Mann-Whitney Test Results comparing effects of isolation and area on occupied and extinct Heath Fritillary sites on Exmoor 1989-2000

TEST U VALUE RESULT SIGNIFICANCE Comparing distance to nearest occupied site 167.0 p=0.0213 <5% Comparing the area of the site 264.0 p=0.0341 <5%

3.5 Change in Vegetation Structure

Table 3.6 shows the comparison of vegetation changes between 1989 and 2000. (The full data can be found in Appendix Five). A Chi Squared test shows that the vegetation height categories were significantly different between years with 11 sites showing an increase (p=0.004, df=2). The percentage bracken cover was also significantly different with nine sites showing an increase between 1989 and 2000 (p=0.047, df=2). The percentage bilberry cover was significantly different with seven sites showing a reduction between the two survey periods (p=0.034, df=2). These results were all significant at the 5% level. No significant differences were found with cow wheat abundance or heather cover between the two periods (p=0.327, df=2, p=0.132, df=l respectively).

The vegetation changes in occupied and extinct sites are shown in Table 3.7. Chi Squared tests were carried out on contingency tables for each factor to see whether the changes are correlated with extinction. However none of the factors showed any significant effect, which may be due to the low number of sites. Thus, site occupancy does not appear to be directly related to these measured changes in vegetation.

Between 1989 and 2000 vegetation height has increased significantly, the percentage bracken cover has increased and conversely, the percentage bilberry cover has decreased on the majority of sites. No significant changes were noted for the cover of cow-wheat or heather. These changes cannot be directly related to site occupancy, but indicate a general deterioration of site quality for the Heath Fritillary. This may partially explain the low population numbers on many sites as the habitat is generally deteriorating.

19

Table 3.6 Comparison in vegetation data between 1989 and 2000

FACTOR

NO. OF SITES WITH DATA

INCREASE

REDUCTION

NO CHANGE

COW-WHEAT RANK

17

6

3

8

VEGETATION HEIGHT

15

11

i _> 1

% BRACKEN 16 9 6 1 % BILBERRY 8 1 7 % HEATHER 11 ->

j 8

Table 3.7 Comparison between occupied and unoccupied site vegetation data between 1989 and 2000

FACTOR

OCCUPIED

NO. OF SITES WITH DATA

INCREASE

REDUCTION

NO CHANGE

0 11 3 2 6 COW-WHEAT RANK N/O 6 -t

3 1 2 O 10 8 9 0 VEGETATION

HEIGHT N/O 5 3 1 1 O 11 8 j 0 % BRACKEN

N/O 5 1 j 1 O 7 1 6 % BILBERRY

N/O 1 0 1 O 7 3 4 % HEATHER

N/O 4 0 4

3.6 Management History on Exmoor

3.6.1 Grazing regimes on Heath Fritillary sites

The grazing histories of eight Heath Fritillary sites were examined in detail. On other sites, details were difficult to obtain because they are Commons where animals roam over a large area and it is difficult to estimate their local impact. Because of these problems a case-study approach has been taken below. The sites have been chosen because they are considered to be representative of the Heath Fritillary sites as a whole.

Tabl&3.8 shows overall changes in grazing on the eight study sites before and after entry into the Exmoor ES A (the full data can be found in Appendix Six, Section 7.6.1). The main impact of entry into the ESA is that winter grazing has ceased on half of these sites (apart from one site with pony grazing).

In addition to the eight study sites, all sites that are now currently in the ESA (Tier 2, part 1), which includes all the heathland National Trust sites, only have winter grazing by pure-bred Exmoor ponies. The previous grazing history on some of these sites could not be retrieved, but it is likely that they have experienced a similar reduction in grazing pressure.

Table 3.8 Overall changes in grazing following the introduction of the Exmoor ESA on the 8 study sites

No. of sites Pre-1993 Pre-1993 Post- 1993 summer % change summer winter only grazing (excluding grazing grazing (excluding ponies) ponies) 8 8 8 4 -50%

3.6.2 Changes in the burning regime on Heath Fritillary sites

Table 3.9 shows the burning records that were collected during this study. The extent of burns has not been quantified and not all accidental burns will have been documented, but the results indicate the general frequency of burning on Heath Fritillary sites.

In general, larger occupied sites seem to have a more regular history of burning than either small or extinct Heath Fritillary sites. The site with the largest Heath Fritillary population in 2000 is Haddon Hill, which is also one of the most regularly burned. Alcombe Common, Grabbist Hill and Bin Combe are sites with more regular burning and they all support large populations.

Halse Combe and Rodhuish Common have had less regular burning regimes and contain small populations. Sites without the butterfly and with little burning include Porlock Common (Berry Castle and Shillett Castle), Nutscale Reservoir and Yealscombe. At Yealscombe there is no burning programme and burning has been severely reduced at Porlock Common.

There seems to be a strong relationship between regular burning and both size and persistence of Heath Fritillary populations. Sites with large populations tend to have a more regular burning regime, whereas small/extinct sites have either no or sporadic burning.

Table 3.9 Frequency of burning on Heath Fritillary sites (listed in decreasing order of population size)3

:. :: . SITE.

POPULATION SIZE .

FREQUENCY OF BURNING OF THE SITE

Haddon Hill large 88,89,91,92,93,95,99 Grabbist Hill larae 87, 92, 97 Alcombe Common large 92, 97, 2000 Bin Combe large 95, 2000 (planned 2001) Hanny Combe large 74, 76, 84, 97 Spangate medium 84,97 Luccombe Plantation small / Aller Combe small 77, 88, 95 Hollow Girt small Sweetworthy small 85,88 Hollow Combe small 82 Periton Combe small 92,97 Halse Combe small 87, 98 (planned 2001) Rey Combe small Rodhuish Common

small

middle 80s, 99, plan to burn a section every year

Bagley Combe not occupied 91? Berry Castle not occupied 90,99 Godsend Moor not occupied 85,95,97 Holmers Combe not occupied / Horner H i l l not occupied Horner Side not occupied 82 Lillycombe not occupied 95/96 Metcombe not occupied / Nutscale Reservoir not occupied No burning carried out Shillett Combe not occupied 85? Weir Wood not occupied 89 Yealscombe not occupied Accidental burn in 98 Yealscombe Water not occupied Accidental burn in 98

3.6.3 Management agreements on Heath Fritillary sites

The survey found that all Heath Fritillary sites (occupied or not) are now under a management agreement, either with English Nature or within the ESA/CSS (Table 3.10). The populations surrounding Dunkery Beacon are all within the ESA boundary and all are entered on the scheme. The Dunkery, Yealscombe and Porlock Common populations are all on SSSIs. Nine of the 13 colonies in the Dunkery area are within the Dunkery and Horner Wood NNR (ENPA, 2001). The full data can be found in Appendix Six, Section 7.6.2.

•Table 3.10 Summary table showing sites entered into management agreements

NO OF SITES

ESA OR CSS AGREEMENT

EN MANAGEMENT AGREEMENT

OTHER

15 occupied 14 0 1 14 unoccupied 1 9 4

' The extent of burns has not been quantified, most have affected only parts of the site.

22

3.6.4 Impact of Deer Activity

It is extremely difficult to quantify the impact of deer activity on Heath Fritillary sites because of the lack of research about numbers in particular locations. Deer are likely to play an important role in grazing and browsing and may have an impact on thinning bracken stands by flattening places to sleep and moving through the vegetation, although evidence for this is largely anecdotal.

A study carried out by Langbein (1997) suggests that the number of deer on Exmoor have increased significantly from 1950 until 1990. Throughout the 1990s deer numbers appear to have remained stable, although their areas of activity and impact may have changed. At the end of the 1990s there was a minimum of 3000 deer on Exmoor and in the Quantocks. Their distribution is very uneven with many concentrated around wooded valleys such as Dunkery. Radio-tracking data suggests that deer spend 25% of their time in bracken/gorse combes although the actual amount of that habitat available constitutes a much smaller percentage. This suggests that deer may be concentrated in the combes near to wooded valleys, which is the habitat occupied by Heath Fritillaries.

Deer diet constitutes mainly of grass in the summer although heather and bilberry contributes 26% in the winter. The deer may play an important role through browsing on bilberry. If the bilberry plants become too dense they will not remain suitable for parasitism by cow-wheat which appear to develop in more 'open" patches of bilberry (Gates, pers. comm.). Further study is required to determine the impact of deer activity on maintaining Heath Fritillary sites.

3.6.5 Case Studies of Exmoor Heath Fritillary Sites and Overview of Management Changes

Summaries from the eight case study sites are in Table 3.11 (the details can be found in Appendix Eight, Section 7.8). The main conclusions are that:

• There has been a clear reduction in the level of grazing on all Heath Fritillary sites.

• There has been a reduction in the frequency of burning on the majority of sites (with the exception of Haddon Hill and Alcombe Common for example).

• There has been an increase in the amount of dense vegetation and considerable scrub encroachment on many sites.

• There is little shepherding of stock, so they are free to wander over large areas looking for the best places to graze. Most combes where Heath Fritillaries breed have little keep to encourage the animals to stay and trample amongst the bracken or control scrub.

• There has been a change in breeds of stock in many cases. This may lead to farmers keeping continental stock and those that are not as good

as trampling through the combes keeping down the bracken and scrub (see Appendix 7.8, Case Studies of Heath Fritillary Sites). The aims of the ESA are to prevent further heather/moorland vegetation deterioration through excessive grazing and poaching. However the case studies show that the effect has been to greatly reduce grazing pressure in the combes with a strong adverse effect on Heath Fritillary breeding habitat. Undergrazing in combes is leading to bracken and scrub encroachment which could have an adverse impact on many other species of moorland fringe (Boyce, 2000). The ESA will need to find ways of restoring or maintaining grazing levels in certain areas on Exmoor in order to maintain a wide range of open heathland habitats and prevent deterioration.

4.0 DISCUSSION

4.1 Population Results

Results of the 2000 survey show that there has been a serious decline in the number of colonies and the population sizes over the approximate twenty year recorded history of the Heath Fritillary on Exmoor. The number of colonies has almost halved since 1989 from 29 to 15, and the majority of populations in 2000 had decreased in size and many were small (see Table 3.1, Table 3.3 and Figure 3.1).

The pattern of extinction of Heath Fritillary colonies over the last 20 years shows that a site was more likely to remain occupied if it contains a large area of breeding habitat and is close to other occupied sites. The results indicate that metapopulation dynamics, as well as habitat management, are playing a crucial role in the survival of the Heath Fritillary on Exmoor.

4.2 The Implications of Metapopulation Dynamics for Heath Fritillary Conservation

Studies of Heath Fritillary population persistence in this report show that occupancy in 2000 appears to be determined by a site being large and near to other occupied sites (see Table 3.5 and Figure 3.3). The implications for conservation are that management needs to be carried out on as large a scale as possible across the Exmoor landscape, so that large areas of suitable habitat are maintained, preferably in close proximity.

The maximum colonisation distance of the Heath Fritillary is poorly known and, although the butterfly is thought to be quite sedentary, some individuals are known to have travelled over 2 km (Warren, 1987). Luccombe Plantation was re-colonised when the site became suitable, presumably colonised from the next nearest site only 700m away. The unoccupied sites in 2000 range in distance from the nearest occupied neighbour from around 500m to just less than 10km. It can be assumed that any site under 2km has a reasonable chance of being re-colonised under the right conditions (Bagley Combe, Godsend Moor, Horner Hill and Horner Side). All the other sites are less than 2km away from another unoccupied site, so if one of these is colonised the others stand a chance of being colonised as well. However the two unoccupied sites at Yealscombe are more isolated and the nearest occupied site is still a number of kilometres away, making natural re-colonisation less likely in the short term.

As mentioned in Section 1.3, the Heath Fritillary sites can be grouped into seven areas, which may represent separate metapopulations (although further research would be needed to confirm this). The seven areas suggested are Dunkery, Alcombe, Haddon, Rodhuish, Porlock Common, the Lillycombe Estate and Yealscombe (ENPA, 2001). All the sites in the Alcombe, Haddon and Rodhuish areas were occupied in the 1999/2000 surveys. Ten out of 14 Dunkery sites were occupied and no sites in the Porlock Common, Lillycombe Estate or Yealscombe areas were occupied. This implies that re-colonisation will be less likely for those areas which currently contain no occupied sites, (i.e. those sites in the north and west of Exmoor -Porlock Common, Lillycombe Estate or Yealscombe). The unoccupied sites around

Dunkery Beacon should be the first to be re-colonised once the habitat is suitable (Bagley Combe, Horner Hill, Horner Side and Godsend Moor).

The results indicate that a landscape approach is needed to conserve the Heath Fritillary on Exmoor, where each individual site is seen in relation to others in the region. If appropriate grazing and burning regimes can be instigated this should create good habitat conditions that will aid the re-colonisation of the currently unoccupied sites. Since 1989, two new colonies have been discovered (on sites not previously recorded), which suggests that there is a potential for creation of additional habitat on Exmoor. Such sites are an essential component of a metapopulation, when in a stable situation, colonisations equal the number of extinctions.

The pattern of isolation and area of sites in 1989 and 2000 (Figures 3.3 and 3.4) demonstrates that levels of isolation are increasing as sites are lost. This increasing isolation then reduces the rates that a relatively immobile species like the Heath Fritillary can re-colonise former sites or colonise new habitats. Thus the Heath Fritillary on Exmoor is in an even more perilous condition than the loss of 50% of sites implies, as the metapopulation breaks down escalating the rate of extinction. The analysis demonstrates still further the need for urgent action across Exmoor.

4.3 Management changes

Case studies on Heath Fritillary sites and habitat data from surveys show that the reduction in grazing pressure and lowering of frequency of burning cycles has resulted in scrub encroachment and a taller and ranker sward on many sites. There is thus an urgent need to reverse the habitat deterioration by instigating appropriate management regimes. These management regimes need to be implemented over as large an area of potential habitat as possible.

The reduction of grazing is driven by the introduction of the ESA and its emphasis on reducing grazing pressures to restore overgrazed heathland vegetation. The history of farming practices sheds light onto the vegetation changes that have been noted since the 1970s. In many cases farmers have changed the type of stock that they keep several times on Exmoor in response to economic subsidies. For example increases in headage subsidies in the 1970s coincided with a 44% increase in sheep reared on Exmoor from 1973 to 1988 (ADAS, 1997). This change was concurrent with the initial discovery of Heath Fritillary colonies on Exmoor. It is possible, though not proven, that heavier grazing may have created more suitable habitat for the Heath Fritillary at that time. After the introduction of the ESA (and the halt or reduction in winter grazing) many farmers changed to breeds that are better at over-wintering in sheds but less likely to be effective at trampling and grazing in the combes in summer. The problem is exacerbated by the lack of shepherding which might heft animals to certain areas and spread grazing more evenly and also little keep in the combes to encourage grazing animals.

Current burning cycles are clearly not able to keep up with vegetation growth, which may have been exacerbated by recent mild and wet weather. Low levels of burning have been evident throughout the 1990s on Exmoor. For example, in a review of the Environmental Monitoring carried out in the Exmoor ESA from 1993-1996, a study

of aerial photographs showed that in 1992 only 1% of the moorland was burnt (ADAS, 1997).

Past studies of burning on Heath Fritillary sites (see Warren, 1991) indicate that when a whole site is burnt the population is destroyed but will be re-colonised if there is an occupied site nearby. After re-colonisation, population levels then increase rapidly to vastly exceed the level before the burn took place. On sites that were only partly burnt, the area was easily re-colonised by individuals that had survived on other parts of the site. On all burnt sites the cow-wheat regeneration was considerable, leading to a big increase in numbers of Heath Fritillary (Warren, 1991).

Burning appears to play a crucial role in keeping habitat suitable for the Heath Fritillary and should be encouraged on shorter and more regular cycles than at present. Currently the National Trust and Butterfly Conservation are collaborating on burning experiments at Bin Combe and the effects of burning will be documented. This will help when disseminating advice to landowners of other Heath Fritillary sites. Questions that need to be addressed include the practicalities of burning sites that are now significantly overgrown and the need to spray after burning to stop a strong regrowth of bracken.

4.4 Examples of other priority invertebrates that depend on extensive grazing - implications for the ESA scheme

The transition zone between wooded combe and heathy moorland is the crucial habitat where the Heath Fritillary breeds and thrives. However this habitat appears to be declining in quality as the grazing levels and burning frequencies have been reduced in recent decades. Other threatened invertebrates occur in similar habitats to the Heath Fritillary and similar problems were shown in a recent report on Dartmoor (Boyce, 2000).

The main conclusion from Boyce (2000) is that in the Dartmoor ESA a lowering of the summer stocking level and removal of stock in the winter period may enhance some heathland vegetation but has a detrimental effect on other habitats on the Commons and several priority invertebrates. These surrounding areas are becoming undergrazed and affect species such as the High Brown Fritillary (Argynnis adippe), the Pearl-bordered Fritillary (Boloria euphrosyne), the Fairy Shrimp (Chirocephalus diaphanus), the Southern Damselfly (Coenagrion mercuriale), Kugelann's Ground Beetle (Pterostichus kugelanni) and the Bog Hoverfly (Eristalis cryptarurri). The report demonstrates the importance of maintaining appropriate grazing levels for these species. For example, the Fairy Shrimp requires high levels of grazing close to the temporary pools where it breeds and Kugelann's Ground Beetle occurs on open, rocky outcrops maintained by grazing.

The aim of the Dartmoor ESA is the same as on Exmoor: to improve the botanical richness of the heaths and mires, which is achieved by reducing the grazing in the higher hills. This leads to undergrazing on the outer edges of the moor in the combes and bracken stands. Traditionally the condition of habitats has been assessed by measuring the botanical communities, but this may overlook the health of invertebrates and other key animal groups. On Dartmoor a smaller proportion of common land has been entered into the ESA compared to Exmoor. Currently grazing

levels on Dartmoor still appear relatively high. The report by Boyce suggests that if there is a widespread cessation of winter grazing and reduced summer grazing, the impact on some threatened invertebrate communities could be highly detrimental. This seems to be exactly what has happened on Exmoor and is exemplified through the dramatic decline of the Heath Fritillary.

The reduction in grazing may have improved the heather quality on the tops of the hills but the combes are changing in an adverse way for a number of threatened invertebrates.

A review of the Environmental Monitoring carried out in the Exmoor ESA from 1993-1996 (ADAS, 1997) states that there is still widespread evidence of high grazing pressure on heather. The report notes that frequent burning in the past, along with high levels of grazing and poaching has led to severe degradation of dwarf-shrub heath. It also notes that there is now a relatively low level of burning which leads to a predominance of old heather which is more vulnerable to grazing. This suggests that there might be pressure for a further reduction of grazing levels in the Exmoor ESA, which will be precisely opposite to the recommendations made in this report for the Heath Fritillary and other threatened invertebrates.

Proposals for changes to the Exmoor ESA prescriptions include greater flexibility to promote biodiversity objectives, including modifications to the agreement if there is a species of particular importance present. FRCA (Farming and Rural Conservation Agency) intends to allocate resources specifically for the positive promotion of such work. In order to assist with these changes of the ESA, Butterfly Conservation and others involved need to supply FRCA with as much information as possible. Hopefully this study will provide such a base and promote a closer partnership between FRCA, Butterfly Conservation and others involved with Heath Fritillary conservation.

It is essential that information about the location and requirements of these threatened invertebrates are made known to the FRCA Project Officers responsible for adminstering the ESA scheme. It is also vital that derogations are actively encouraged to increase grazing levels where necessary on Heath Fritillary sites. Monitoring needs to be carried out on Exmoor BAP invertebrates to assess in more detail the impact of the ESA scheme.

4.5 Fulfilling SAP Objectives and Contributing to the Exmoor BAP

Butterfly Conservation's Species Action Plan for the Heath Fritillary (Barnett and Warren, 1995) elaborates the plan in the UK BAP (DOE, 1995) and has the following aims relevant to this report: • to maintain the range of the Heath Fritillary in South-west England

• to maintain appropriate burning and grazing regimes on sites

• to undertake further research into the species' habitat requirements on Exmoor • to include the species" requirements when revising management prescriptions for land

enhancement schemes

• to manage all sites positively and to encourage suitable management on nearby sites to encourage colonisation

• to advise land management agencies on practical habitat management • to continue transects and monitoring of all colonies every 2-5 years

This study aims to help further all of these objectives and follow up work is clearly needed to disseminate the results of this report to those who are undertaking practical habitat management on Exmoor or who are involved with Heath Fritillary conservation.

The Exmoor Biodiversity Action Plan aims to increase Exmoor's biodiversity, targeting those species and habitats most valued nationally and locally, by building partnerships with others (ENPA, 2001). The aims of the Exmoor BAP with respect to the Heath Fritillary include: • maintaining all existing metapopulations

• increasing the size of all the metapopulations

• establishing new colonies

• increasing public awareness

• creating new areas of suitable habitat • establishing some oak coppicing close to existing Heath Fritillary colonies

• incorporating the needs of the Heath Fritillary into reviews of land enhancement schemes

• encouraging positive management for the butterfly through the uptake of ESA BAP payments

• monitoring all Heath Fritillary colonies

• carrying out further research on the ecology of the Heath Fritillary.

This study has helped by elucidating the current Heath Fritillary status on Exmoor, increasing public awareness, identifying key management priorities and current threats to Heath Fritillary populations. We are confident that given sufficient additional resources, it is possible to dramatically improve the status of the Heath Fritillary and implement both plans.

The importance of forming partnerships is also identified in the BAP and this has been acted on by Butterfly Conservation, which has organised several meetings with a wide range of interested parties on Exmoor. The minutes of a meeting organised by

Butterfly Conservation and FRCA entitled "Priority Butterflies and Moorland Management" can be found in Appendix Nine.

4.6 Future Research and Monitoring

• More research needs to be undertaken into what constitutes good quality habitat for the Heath Fritillary on Exmoor. The scale used for measuring cow-wheat abundance in this study did not appear to be sensitive enough and it may be more appropriate to use quadrats and domin values to estimate % coverage.

• Continued detailed surveys are essential to determine responses of colonies to management and to monitor metapopulation dynamics. More extensive surveys of occupied and unoccupied habitat would enable colonisation events to be assessed.

• It is important that at least one transect is walked for the duration of the flight period for the Heath Fritillary, according to the BMS criteria. This allows the timed count data to be adjusted to peak with confidence according to when they were walked in the flight period.

• More research needs to be undertaken into the impact of deer grazing on Heath Fritillaries sites. This will enable total grazing pressure to be calculated more accurately and will help to define appropriate stocking numbers for moorland combes.

4.7 General Recommendations

• Target management on those sites that are most likely to be naturally re-colonised once the habitat is suitable.

• Instigate and perpetuate appropriate grazing regimes on actual and potential Heath Fritillary sites.

• Encourage a more regular burning programme on actual and potential sites (an 8-10 year cycle would be the minimum to aim for).

• Encourage wider dissemination of the information about the importance of threatened BAP invertebrates in moorland fringe habitats.

• Improve knowledge of Exmoor ESA Project Officers over the location of BAP invertebrates and their habitat/management requirements.

• Incorporate special grazing regimes for threatened butterflies and invertebrates in future ESA reviews.

• Improve monitoring and survey levels of actual and potential Heath Fritillary sites, especially the maintenance of at least one regular transect.

• Further reviews of monitoring on all previous sites.

5.0 ACKNOWLEDGEMENTS

We would like to thank English Nature and Wessex Water for their continuing financial support and interest in the project, and also for a donation from a local charitable trust. We are very grateful to all the people who helped with the surveying and have supplied information used in this report. These include Matthew Dates, Nigel Hestor, Paul Camp, Mike Winzer, Jessica Rushton (National Trust); Mike Edgington and Flemming Ulf-Hansen (English Nature); David Lloyd (Exmoor National Park); Noel Alien, Caroline Giddens, Michael Hankin and Douglas Bond (Exmoor Natural History Society); Dudley Cheesman, David Land, Richard Fox and Roger Sutton (Butterfly Conservation), Dave Boyce (freelance ecologist) and the owners/tenants who gave management information.

Tom Brereton's input to the project was funded under a grant from the Ministry of Agriculture, Fisheries and Food (BD1427). We would also like to thank Ralph Clarke at the Centre for Ecology and Hydrology, Dorset (CEH) who gave statistical advice and helped with the production of Figure 3.3. Figure 3.1 was produced using Dmap for Windows, © Dr Alan Morton.

6.0 REFERENCES

ADAS. (1997). Environmental Monitoring in the Exmoor ESA 1993-1996. ADAS Report to MAFF.

Barnett, L.K. and Warren, M.S. (1995). Species Action Plan: Heath Fritillary Mellicta athalia. Butterfly Conservation, Wareham.

Boyce, D.C. (2000). A Review of the Importance of Dartmoor's Common Land and Wet Pastures for Priority and Threatened Invertebrates. An Unpublished Report for Butterfly Conservation, Dartmoor National Park and English Nature.

Brereton, T.M., Warren, M.S. and Roberts, R.E. (1998). Action for the Heath Fritillary: Status, Monitoring and Conservation Progress 1996 & 1997. Butterfly Conservation, Wareham.

DOE. (1995). Biodiversity: The UK Steering Group Report. HMSO, London.

ENPA (Exmoor National Park Authority). (2001). Exmoor Biodiversity Action Plan. Exmoor National Park Authority.

Feber, R., Bourn, N., Brereton, T. and Warren, M. (2000). Site Dossier and Status of the Heath Fritillary (Mellicta athalia) on Exmoor in 1999. Butterfly Conservation, Wareham.

Gilpin, M. and Hanski, I. (Eds) (1991). Metapopulation dynamics: Empirical and theoretical investigations. Academic Press, London.

Langbein, J. (1997). The Ranging Behaviour, Habitat-use and Impact of Deer in Oak Woods and Heather Moors of Exmoor and the Quantock Hills. University of Southampton -Biodiversity and Ecology. Moss, D. and Pollard, E. (1993). Calculation of Collated Indices of Abundance of Butterflies based on Monitored Sites. Ecological Entomology 18, 77-83.

Warren, M.S. (1985). The Ecology and Conservation of the Heath Fritillary (Mellicta athalid). Unpublished Report - Nature Conservancy Council.

Warren, M.S. (1987). The Ecology and Conservation of-the Heath Fritillary (Mellicta athalid). II. Adult Population Structure and Mobility. Journal of Applied Ecology 24, 483-498.

Warren, M.S. (1989). National Heath Fritillary Survey and Progress Report, 1989. Unpublished Report to WWF (World Wide Fund for Nature).

Warren, M.S. (1991). The Successful Conservation of an Endangered Species, the Heath Fritillary Butterfly (Mellicta athalid), in Britain. Biological Conservation 55, 37-56.

Warren, M.S., Thomas, C.D. and Thomas, J.A. (1981). The Heath Fritillary. Survey and Conservation Report. Report for the Joint Committee for the Conservation of British Insects. Warren, M.S., Thomas, C.D. and Thomas, J.A. (1984). The Status of the Heath Fritillary Butterfly Mellicta athalia Rott. in Britain. Biological Conservation 29 pp. 287-305. 7.7 Appendix Seven- Questions asked to Farmers/Landowners during the Management Survey

GENERAL MANAGEMENT OVER PAST 20 YEARS: • Details of numbers of stock grazing and rough locations • Type of stock grazing • Times of year • Amount of supplementary winter feeding and pasture land available • Valuable areas of the moor for animal grazing and shelter

ESA: Are you entered into the ESA? How have things changed since being in the ESA scheme? • Numbers of stock grazed: • Types of stock grazed: • Time of year of grazing: How do you think the ESA scheme has benefitted you?

GENERAL IMPRESSIONS OF CHANGES OF THE MOOR OVER THE PAST 20 YEARS: Any thoughts about significant changes on the moor over the last 20 years, particularly in relation to vegetation changes, abundances of animals, situations of farmers/tenants etc:

ANY OTHER THOUGHTS IN RELATION TO MANAGEMENT AND CONSERVATION:

7.8 Appendix Eight - Case Studies of Exmoor Heath Fritillary Sites

HALSE COMBE (SS895456)

In 1993 Halse Combe supported the largest Heath Fritillary population on Exmoor, estimated to be around 11,600 individuals. In 2000 only one individual was seen which gave an estimated population size of 25, one of the smallest populations in that year.

Habitat Examination of aerial photographs of the area show scrub invasion and a general increase in the amount of tall vegetation present. Slides taken in 1984 reveal dense patches of bilberry with a small amount of scrub and heather cover. Slides in 1987 show fairly dense bracken cover with many open areas of bilberry and cow wheat. Pictures taken last year indicate widespread scrub and bracken with small amounts of open areas. The vegetation changes from the early 1980s to 2000 has been an increase in the amount and height of the vegetation, including scrub.

Analysis of aerial photos, old slides and interviews with site managers suggest that the amount of cow-wheat present has greatly reduced over the last 10 years. In the late 1980s cow-wheat was widely distributed throughout the combe and occurred quite a distance up the slopes towards the top of the combe. During the 1999/2000 surveys cow-wheat was only found in one small area, which was also where the only Heath Fritillary was seen in 2000. There was no detailed vegetation monitoring at Halse . Combe in 1989 from which to make comparisons, but there has been a significant reduction in the amount of cow-wheat present. The average vegetation height in 2000 was 80cm. The general trend on all sites in vegetation height and bracken coverage data is a significant increase since 1989, which supports the evidence seen from photos and slides at Halse Combe.

Grazing During the period in the 1980s before 1987 a Red Devon suckler herd of 60-70 animals grazed the area (Ley and Crawler Hills). The farmer reports that the cattle were extremely good at breaking up the bracken beds when they were present in these numbers. 25 years ago bracken was cut and used for animal bedding. Between 1987 and 1993 the herd consisted of 30-40 animals. The cattle over-wintered on the moor and were fed throughout the winter. Roughly 200 ewes were also over-wintered from November until spring and some early weaned lambs from July onwards.

After the introduction of the ESA there has been no winter grazing (apart from the occasional Exmoor pony). There is very little keep (appetising grasses etc.) in the combe and therefore any free-ranging stock are not encouraged to go down to feed. The Red Devon herd was replaced with Black Herefords that sometimes graze the moor in the summer. 150 ewes could graze the area according to ESA rules, but there is no consistent summer grazing by cattle or sheep in the combe.

Burning The farmer reported a reduction in the frequency of burning of this part of the moor. This may be due to stricter guidelines on when burning is allowed and the difficulties in safely controlling a burn in this area. There is now much more material to actually

burn, making it practically more difficult. Burning was carried out on the Heath Fritillary site in 1987 and 1998 and is planned for 2001. Even given the possibility of over-looking some accidental burns in this analysis, the level of burning is not a 10-15 year cycle for the whole of the combe.

A general increase in the height and density of the vegetation has been noted at Halse Combe, which is backed up by the vegetation analyses undertaken in Section 3.5. After Halse Combe entered the ESA no winter grazing was undertaken and now there is very little keep in the combe to even encourage the occasional Exmoor pony. There has also been very little burning in the combe.

HADDON HILL (SS975286)

Haddon Hill holds the largest population on Exmoor in 2000 with an estimated population size of 3652 individuals. The site also had a large population (estimated size of 9843) in 1989. It is one of the largest but most isolated of all the Heath Fritillary sites, and is situated south of the Brendons near Wimbleball Lake.

Habitat and Burning There are several patches of good quality habitat on Haddon Hill. On the west side of the site there is some very suitable habitat which was burnt four years ago. There are some patches of very dense cow-wheat and the bracken is open and patchy. Slides from 1989 show a similar picture with dense cow wheat in patches, bracken with open areas and some heather.

Vegetation analysis was undertaken in 1989 and since then there has been an increase in the amount of cow-wheat present, an increase in vegetation height of one and a half times, an increase of about one quarter of both heather and bracken and a third reduction in the amount of bilberry present.

Burning is undertaken very regularly on the site. Between the period 1988 to 1999 planned burning has been undertaken every year from 1989 and 1993 and also in 1999. Accidental burning (which may have been at the wrong time of year for most wildlife) occurred in 1988, 1991, 1992, 1995 and 1999 (see attached map).

Grazing For the past 10 years there has been a management agreement on the site with the private owner and the Exmoor National Park. The private owner is now entering the ESA scheme (the two ends of the hill are privately owned and Exmoor National Park owns the centre section). 10-15 ponies graze the site and there is also summer to autumn sheep grazing every year (of about 100 - 150 individuals). There has not been any cattle grazing.

Haddon Hill has regular but light grazing from ponies all year and sheep in the summer. There is a regular burning regime on this site. Cow-wheat has increased here since 1989 but there has also been an increase in the vegetation height, amount of heather and bracken and a decrease in bilberry coverage.

RODHUISH COMMON (SS994402)

Two individuals were recorded here on the 24/6/99 by Dave Boyce but a subsequent visit in 1999 and three visits during the field season in 2000 failed to record any individuals. This indicates that the Rodhuish Common population is in a perilous position. Rodhuish Common is under Countryside Stewardship Agreement, which started in September 1992. The Rodhuish Common area has recently become an SSSI.

Habitat The bracken is extremely dense at this site and there are occasional gorse bushes and other scrub present with trees at the bottom. The farmer notes that the vegetation appears to be much more dense and overgrown than 20 years ago. The heather used to occur down to the bottom of slopes and there was very little bracken and grass along the moor edges. There is a lot more gorse around which seems to grow throughout the winter.

Grazing Before entering the Stewardship Agreement the farmer overwintered 60-70 cattle on the moor and fed them with hay/straw scattered around, sugarbeet and magnesium block. They had sheep on the Common all summer.

In the last 8 years after entering the Countryside Stewardship Agreement, there has been no winter cattle grazing (apart from 6-7 years ago when there was a drought and the cattle were on the Common for about 1 month in September). There are about 60 sheep grazed on the Common in the summer months (end of May to September). The cattle are over-wintered in barns. The farmer has noticed that the soil structure has changed since they have not over-wintered cattle on the moor. The farmer used to graze Red Devon cattle but now has Hereford-Fresian crosses and some continental stock. The sheep have been changed from Dorset Downs to Suffolk crosses and blue-faced Leicester.

The farmer feels that there appear to be a lot more deer in the area than 20 years ago. This could be because deer numbers have increased or simply that their distribution has changed following the banning of deer hunting on the nearby National Trust land.

Burning and other Management At the beginning of the Stewardship Agreement the farmer was given money to assist with mechanical bracken cutting and spraying. There has been no bracken control in the area recently, although funds may be available. The Exmoor National Park burnt an area last spring above the Heath Fritillary site to try to remove some of the gorse. They intend to burn a section every year. In the 1980s they burnt a large section of the whole hill but bracken and scrub is beginning to be a problem again. In areas that are burnt, the heather and cow-wheat have appeared to come back and recover well.

There is dense bracken and scrub at this site with little cow-wheat present. There is only summer sheep grazing and although there was some burning in 1999, little had been carried out before that. At this site it appears that increased grazing pressure by stock is not an agreeable option to improve the Heath Fritillary habitat quality. The proposed programme of burning a section every

year (with an Azulox spray to follow up) will help greatly as would any mechanical scrub clearance. The management needs to be carried out as soon as possible because the Heath Fritillary population seems to be in a precarious position.

YEALSCOMBE (SS792464/SS792459)

The butterfly was last seen on the site in 1998 (J. Holtom pers. comm.), not being recorded during the surveys of 1999 and 2000. The site is divided into two discrete areas, Yealscombe and Yealscombe Water.

Habitat The habitat quality does appear sufficient to support a colony of Heath Fritillaries. There is cow wheat present, especially at the transition zone from woodland to moorland. The cow wheat is particularly dense under the trees and also on the edges of the moorland.

Grazing Yealscombe is part of Brendon Common and there are currently 11 active graziers. Most of these animals are hefted to other areas and Yealscombe is lightly grazed. Heaviest grazing in bad weather when stock move to shelter under the trees. The approximate grazing figures for 1,380 hectares are 1230 sheep and 189 cattle in winter and 189 cattle and 2510 sheep in summer, with 62 ponies all year round. It is difficult to actually assess the grazing levels on the Heath Fritillary sites as the animals have such a wide area to wander across.

Since 1997 attempts have been made to put the area into the ESA scheme and Environmental Cross compliance, which has led to a slight reduction in stocking levels. If the ESA was taken up the stocking would consist of cattle (155) and sheep (1027) in summer and no cattle in winter but sheep numbers would remain the same.

Burning On this site no controlled burning has been carried out (there was an accidental burn in 1998). Some scrub clearance has been undertaken and future burning management is planned.

The habitat appears to be suitable for the Heath Fritillary with fairly dense patches of cow-wheat present in areas. The grazing seems to have been fairly constant in the last 10 years although the actual pressure on the Heath Fritillary site is difficult to assess. There has been no regular burning on this site, although a burning regime is planned for the future.

PORLOCK COMMON (SS859449/ SS860450)

Porlock Common consists of two Heath Fritillary sites, namely Berry Castle and Shillett Combe. The last Heath Fritillary record was in 1998 in Shillett Combe when David Lloyd (Exmoor National Park) saw two individuals.

Habitat Berry Castle has a dense covering of bracken with lots of scrub, especially gorse. Slides from 1989 show that there was quite a dense covering of bracken 10 years ago with significant amounts of heather as well. Shillett Combe has some dense bracken areas and some parts are very shrubby with plenty of gorse present.

Burning Burning records are from 1985, 1990 and 1999. In the past rotational burning was carried out every 6-8 years, but recently the area has become significantly overgrown and Porlock Common is now very susceptible to summer fires.

Grazing 20 years ago Shillett Combe and Berry Castle stocked with 500 sheep and 25 cattle. Cattle were winter fed in different areas (on top of Shillett Wood or down in Hawkcombe). Shillett Wood was fenced 12-13 years ago and cattle were no longer grazed. Until recently it was summer grazed with sheep (July to September). There is an English Nature management agreement but the area is not in Stewardship or in the ESA. The English Nature management agreement allows stocking of the Common at ESA levels (0.225 per ha in summer, 0.1 in winter) but the cattle have to be taken off a month early. In 2000 there were in summer 12 Exmoors and followers, 20 cows and 300 sheep (16/4 - 1/10) and in winter, 300 sheep and 12 Exmoors.

Porlock Common echoes the general vegetation trends seen, with an increase in scrub and the rankness and height of vegetation. The time between cycles of burning has significantly reduced and the level of grazing has been lowered also.

7.9 Appendix Nine - Priority Butterflies and Moorland Management on Exmoor and Dartmoor Notes of Meeting held at Piles Mill, Exmoor on 20th October 2000

Background to the meeting Exmoor and Dartmoor are one of the last strongholds of several priority BAP butterflies, notably the Heath Fritillary, High Brown Fritillary, and Pearl-bordered Fritillary. These species breed in bracken or bilberry habitats around the moorland fringe, which seem to require moderate to high levels of management in the form of grazing or burning. Butterfly Conservation has been monitoring the populations of these species for 10-20 years and there is evidence of continuing population decline.

Aims of the meeting • To share information about these issues. • To discuss the problems and seek possible solutions. • To inform future monitoring and research work conducted by BC and other

organisations.

The Heath Fritillary The Heath Fritillary occurs in sheltered combes on Exmoor where its larval foodplant cow-wheat grows amongst bilberry. In the last 10 years the number of occupied sites has dropped from 30 to roughly 15 colonies. Population data was presented which spanned 1984 to 2000 for each Exmoor site. For most sites it was clear that during the late 1980s and early 1990s the colonies had high population levels but had dropped down to a low level or extinction in the middle to late 1990s. The results for this year's survey were presented which showed 14 occupied sites with some populations at a very low level. In 2000 there were 7 small (10-100 adults) populations, 2 medium (101-250) populations and 5 large (>250) populations.

Slides were presented by Martin Warren that showed gross vegetation changes over time on several Heath Fritillary sites. Aller Combe (which was grazed in the past) has much more scrub now than in 1980 and the bracken is increasing and becoming denser. The numbers have dropped significantly from a large population in the 1980s to a small one today. The same is noted at Bin Combe where the heather has spread, the bilberry is taller and the vegetation is getting thicker and denser, but Bin Combe still supports a large population. Horner Side has suffered from significant gorse encroachment and the population there is extinct. Alcombe Common has been regularly burnt and been grazed by deer and is one of the few sites that still supports a large population. Haddon Hill has also been regularly burnt and has some minimal grazing and now supports a large population.

The High Brown Fritillary The High Brown Fritillary occurs on bracken slopes where violets are present. On Exmoor there are only a small number of colonies (e.g. Bossington Hill and Trentishoe Common) but Dartmoor holds two thirds of the British resource of colonies. Dave Boyce (a freelance ecologist) carried out a survey of all known sites on Dartmoor this summer and found the butterfly in 7 out of 16 sites, with one new site. He believes that poor weather (and in some cases a lack of management) has caused the High Brown Fritillary to retract into a number of core sites where there is optimal breeding habitat. Some of the unoccupied sites were on higher land, where

cold and wet spring weather would have had more of an impact. The High Brown Fritillary has disappeared or is doing badly on sites in the Teign Valley which may be due to the lack of appropriate management on some sites. Dave Boyce believes that on Dartmoor there are three or four metapopulations and two of them support very low numbers.

The Pearl-Bordered Fritillary The Pearl-bordered Fritillary also inhabits bracken slopes with violets growing out of the bracken litter. There are few Pearl-bordered Fritillary sites on Exmoor but there are a good number on Dartmoor. The Pearl-bordered Fritillary is another species that is in severe decline all over the country.

Research Needs Although we have some information about population estimates for these species over time, we have comparatively little information about vegetation changes and the role this will have on the butterfly populations. It is a goal to set up more research projects to investigate some of these problems and to have vegetation monitoring baselines that can be compared again in the future. Butterfly Conservation has established some baseline recording of vegetation on all known High Brown sites and need to do the same for Heath Fritillary and Pearl-bordered Fritillary. Good research will be invaluable for those trying to manage the fritillary habitats.

Management Issues Affecting Other Priority BAP Invertebrates Dave Boyce mentioned other endangered invertebrates that occur in similar habitats to the threatened fritillaries. In the Aish Tor area on Dartmoor several BAP species exist including the hornet robber fly, Kugelannis beetle and the blue ground beetle. Interestingly the blue ground beetle is heavily dependent on winter grazing to produce suitable habitat. A number of other rare invertebrate species are affected by undergrazing on moorland habitat. Fie is preparing a report on this topic for English Nature, Dartmoor National Park and Butterfly Conservation.

Role Of The ESA And Relevent Moorland Prescriptions Richard Andrews, project officer for the Exmoor ESA, spoke about FRCA's concern of intensification of the moor and the importance of balancing all interests including ecological, agricultural, archaelogical and landscape issues. He explained that the ESA has prescriptions to prevent under or over-grazing and mentioned how supplementary winter feeding had been a significant problem in the past. In order to conserve and increase the amount of heather moorland, no winter grazing is allowed currently (excepting Exmoor ponies). The National Trust and the ESA officers said that they had been concerned over the state of the moor when winter grazing was allowed. Changes of breeds of sheep and cattle, (in response to increased headage subsidies) that can withstand winter conditions, may have led to overgrazing in certain areas.

Grants can be given out for bracken and scrub control but the maximum grant is 80%, which cannot be afforded by some farmers. Problems with the ESA policyholder being different to the farmer who actually carries out the work was mentioned. Derogations are possible if there is a good reason to have winter stocking on a site, for example. There is a need for better communication about what flexibility already exists within the ESA. The Exmoor ESA has been monitored through several

reviews, including one where 13 grazing units have been monitored. The results showed that the reduction in stocking rates have been marginal on Exmoor but have been reduced by up to 50% on Dartmoor.

Management A well-managed High Brown Fritillary site will have a dense cover of bracken in the summer but in the spring the litter will be a patchy mosiac with grass, due to grazing. The parameters in a well managed Heath Fritillary site are less known but it is important to have plenty of cow-wheat growing amongst bilberry in sheltered conditions.

Where bracken has encroached on the moor in Heath Fritillary habitat, one option is to burn and then spray the following year to prevent even stronger growth of bracken. The recent run of wet winter/spring weather means that it has been more difficult to find suitable days to burn the heather. Practical constraints like this and public perception make burning even more difficult to accomplish over a wider area. We await the results from the recent programme of burning carried out by the National Trust in Bin Combe to make the habitat more suitable for Heath Fritillary. There has already been a good regrowth of bilberry. The results may help the Exmoor ESA review of management agreements in 2003. Burning is an important strategy that needs pursuing as bilberry and cow wheat respond well to it. However the post-burn spraying cannot be done if the farm is organic. The bracken bruiser could be considered in some areas. Also creative use of feed blocks can direct animals to areas where they are most needed.

Site Visit To Halse Combe In 1989 the butterfly was found all over the combe but in 1993 it had retreated lower down the slopes. Because access to the combe is difficult there has been little controlled burning although there have been several 'accidental' summer burns. The bracken stands are much denser than in the past and there are less short, open areas. Deer have kept some areas more open and this is where the main Heath Fritillary breeding habitat remains. Most of the year the grazing levels are below that required by the ESA agreement. Management options were discussed and it was felt that patchy burning and then spraying would be a good option. The burn should attract grazing animals in to trample other bracken areas. Some paths could be cut but there are restraints on getting some machinery onto the site. It is also necessary to produce more grass keep within the combe to make grazing animals stay there.

Conclusions • The meeting has highlighted the importance of heavily grazed moorland habitats, not

just for several threatened butterflies but also for other BAP Priority invertebrates. • The vegetation on the moorland fringes seems to be subtly changing on Exmoor and

it is important that management prescriptions maintain the ecotones in the combes and woodland edges.

• Agri-environment schemes may be a rather blunt instrument in changing moorland management to help biodiversity - but BAP targets are being incorporated and important mechanisms are in place (e.g. biodiversity grants, derogations, and Moorland Management Plans).

The broad prescriptions within the ESAs are targeted mainly at the moorland itself, not the moorland fringe where many of these priority invertebrates breed. There has been a major decline in cattle grazing in the UK and ESAs may have to address issues of under-grazing of moorland in the future (rather than current emphasis on preventing over-grazing). We need to know more about the possible impact of the Hill Farm Allowance Scheme (replacing HLCA) on future grazing levels on moorland habitats. More dynamic vegetation management is needed within the ESA, but small scale management will be difficult to achieve, especially given present bleak economic situation facing farmers. However, more emphasis should be placed on scrub clearance, burning, use of bracken spaying and bracken-bruising machines, use of ponies to achieve necessary grazing levels, use of feed blocks to influence grazing patterns. It would be helpful to have a series of demonstration sites to show examples of good management for threatened fritillaries (and other priority invertebrates), including some privately owned sites as well as NT sites etc. Grants for biodiversity are currently 80%, but in the current economic climate it may be necessary to rethink this and increase to 100% if take up is poor. Butterfly Conservation will investigate specific ways in which it can help inform these issues in the future, including: continuing existing monitoring programmes; establishing vegetation monitoring on key sites; preparing maps showing metapopulation areas where management should be targeted; documenting management experiments being done on important butterfly sites (with help of partner organisations); providing data on key butterfly sites to go onto GIS systems used by FRCA and NPs.

ATTENDEES: Paul Camp - National Trust Holnicote Warden Nigel Hestor - National Trust • Richard Morris - National Trust Holnicote Property Manager Matthew Gates - National Trust Conservation Advisor Richard Andrews - FRCA Exmoor Project Officer David Glaves - FRCA Ecologist GeoffRadley - FRCA Ecological Policy Advisor Pete Stevens - FRCA Dartmoor Project Officer Majory Taylor - FRCA Exmoor Project Officer David Lloyd - Exmoor National Park Ecologist / Dave Boyce - Freelance Ecologist Mike Edgington, English Nature (Somerset Team) Nigel Bourn - Species Action Co-ordinator, Butterfly Conservation [•Catherine Stewart - Threatened Fritillaries Project Assistant, Butterfly Conservation Martin Warren - Head of Conservation, Butterfly Conservation

MINUTES ALSO TO BE CIRCULATED TO: David Smallshire - FRCA Ecologist Norman Baldock - Exmoor National Park Ecologist Philip Collins - EN Devon Conservation Team Manager Gavin Saunders - Devon Wildlife Trust

David Westbrook - Somerset Wildlife Trust