Yorkshire Dales National Park Authority Conservation Research & Monitoring Report No. 24

Transcription

1 Yorkshire Dales National Park Authority Conservation Research & Monitoring Report No. 24 Butterfly transect monitoring in the Yorkshire Dales National Park in 2012 I.R. Court 1 T.M. Whitaker 2 April 2013 Correspondence addresses: 1 Yorkshire Dales National Park Authority, Colvend, Hebden Road, Grassington, Skipton, North Yorkshire, BD23 5LB ian.court@yorkshiredales.org.uk 2 T.M Whitaker, 4 Crowtrees, Lancaster. LA2 7EE t.whitaker1@btinternet.com

2 CONTENTS Page No. Executive summary 3 Introduction 3 Methodology 4 Results 6 Discussion 16 Acknowledgements 18 References 19 Appendices 1. Monitoring butterfly numbers by the 23 transect method summary information for recorders 2. Field guidance notes for butterfly transects 24 2

3 EXECUTIVE SUMMARY In the Yorkshire Dales National Park (YDNP) six existing and one new full species monitoring transects were surveyed as part of the United Kingdom Butterfly Monitoring Scheme (UKBMS) in 2012, with one former single species transect discontinued. All transect survey work was coordinated by Butterfly Conservation and Yorkshire Dales National Park Authority staff. The results from the five transects with continuous data show that in 2012: The population of the Small Pearl-bordered Fritillary Boloria selene on Swarth Moor SSSI is stable. The combined trend for Small Heath Coenonympha pamphilus in the YDNP using data collected up until the end of 2011 shows that the population is increasing. The monitoring of Northern Brown Argus Aricia artaxerxes populations are heavily influenced by weather conditions and show large fluctuations in observed numbers. At Lea Green-Bastow Wood the population is stable or slightly increasing but on Scar Close the population appears to be in slight decline. Overall, there are insufficient transects to currently determine a population trend for the YDNP. The Yorkshire Dales Butterfly and Moth Forum concluded, in 2012, concluded that the current populations of the two other Biodiversity Action Plan priority species that occur in the Yorkshire Dales National Park: Wall Lasiommata megera and White Letter Hairstreak Satyrium w-album are too small, and have such a limited distribution that an appropriate monitoring program cannot be established. INTRODUCTION The monitoring of butterfly populations using transects is primarily undertaken to determine changes in the abundance of butterflies across the country. Increasing the number of monitoring sites in these upland areas has been a key objective of the UKBMS as there is limited information on the status of many common butterfly species in upland areas of the country. The scheme is also intended to monitor rare species with a localised distribution. In the latter category, Northern Brown Argus, Small Pearl-bordered Fritillary and Small Heath are also priority species in the National and Local Biodiversity Action Plan (LBAP) for the Yorkshire Dales National Park Nature in the Dales 2020 Vision. The results of the transect monitoring contribute towards the LBAP objective of determining population trends for these species in the YDNP. The populations of the two other Biodiversity Action Plan priority species that occur in the YDNP: Wall Lasiommata megera and White Letter Hairstreak Satyrium w-album are too small, and have such a limited distribution that an appropriate monitoring program cannot be established. The butterfly transect monitoring follows the standard methodology for monitoring butterfly populations and involves weekly counts along a fixed route during the season within set guidelines for time of day, temperature, wind speed and amount of sun. In the YDNP, five transects have been monitored for a number of years, at Ballowfield, Bastow Wood, Craven Limeworks, Scar Close and Swarth Moor. An additional single species transect at 3

4 Northern Brown Argus at Long Ashes (Threshfield) was not surveyed in 2012 and may be permanently discontinued but a new transect, monitored by National Trust staff has been established in 2012 at Yockenthwaite. METHODOLOGY The standard transect methodology for monitoring butterfly populations (Pollard and Yates, 1993) was used at all sites and is summarised in appendix 1 and 2. A trend for Northern Brown Argus and Small Heath in the YDNP has been calculated by Butterfly Conservation using the TRIM (TRends & Indices for Monitoring data) software package, using data from transect sites where these species are present and has been collected to the Butterfly Monitoring Scheme methodology (Biological Records Centre, 2006). Monthly weather summaries for 2012 have been derived from seasonal summaries provided by the Met Office (2012). A summary of the monitoring transects in the YDNP is as follows: Long Ashes (SD977647) Length 1650m Unfortunately the Long Ashes transect has been discontinued. Ballowfield (SD992895) Length 831m This is a small grassland local nature reserve area near Carperby, Wensleydale on an area of lead mining spoil. The transect then crosses Eller Beck into the Ox Close Site of Special Scientific Interest (SSSI), designated for its assemblage of metallophytes and other plants tolerant of metal-rich soils. The site also has an important woodland component where Small-leaved Lime Tilia cordata and Large-leaved Lime Tilia platyphyllos are present along with wet flushes and limestone grassland. Parts of the site support colonies of Northern Brown Argus and although it was original intended that the transect would incorporate monitoring of one of the larger colonies, it was not possible to negotiate access permission for that particular area. Surveyors: Ian Court, Hannah Fawcett and Mark Hewitt. Lea Green & Bastow Wood, Grassington (SD995657) Length 2950m This transect covers an area of Carboniferous Limestone near Grassington, Wharfedale that supports flora typical of limestone grassland including Common Rock Rose Helianthemum nummularium. The transect route passes through one of only two Ash- Hazel woodland pastures in the Yorkshire Dales National Park. Surveyors: Ian Court, Mark Hewitt and Ian Powell. Craven Limeworks, Langcliffe (SD824662) Length 1027m This site near Settle, Ribblesdale is dominated by Stainforth Scar and the Langcliffe Quarry face indicating the long history of lime production at the site, with the well preserved remains of the Hoffman Kiln at the centre of this important archeological site. The transect covers areas of calcareous grassland supporting herbaceous plant communities adjacent to areas of broad leaved woodland and was set up as an all species transect. 4

5 Surveyors: Stuart Armitage, Craig Bellwood, Jill Buckler, Ian Court, Steve Hastie, Pat Higginson, Cat Kilner, Brian Shorrock, Ian Sim and Rhona Thornton. Scar Close, Ingleborough (SD7577) Length 2389m Within the Ingleborough National Nature Reserve the transect goes across Scar Close, an area of sparsely wooded limestone pavement supporting a wide diversity of calcareous grassland species. The site is unique in having areas of peat on the pavement that support more acidic tolerant species. The transect was established primarily for Northern Brown Argus but in recent years has proven to be the largest colony of Dark Green Fritillary Argynnis aglaja in Yorkshire (Whitaker, 2006). The discovery of Small Pearl-bordered Fritillary in 2007 highlights the importance of transect monitoring some of the key butterfly species in the uplands. Surveyors: Simon Bullough, Emma Coombs, Andrew Hinde, Colin Newlands, John Osborne and Terry Whitaker. Swarth Moor National Nature Reserve, Helwith Bridge (SD807693) Length 1504m Situated adjacent to the Ingleborough National Nature Reserve (NNR), Swarth Moor SSSI comprises an area of raised bog, fen and small areas of carr woodland. This site is the core site for Small Pearl-bordered Fritillary in the Yorkshire Dales National Park with the transect having been established primarily to monitor this species. Surveyors: Ian Court, Steve Hastie, Gerald Light, David Sharrod, Brian Shorrock, David Tayler, Terry Whitaker and Royanne Wilding. Yockenthwaite, Langstrothdale (SD910790) Length 2192m This was the first year for a new transect on National Trust land in Langstrothdale and runs between Yockenthwaite and Strans Wood and is predominately calcareous, species rich grassland with scattered trees and scrub. There are a number of Northern Brown Argus colonies along the transect route. Surveyors: Chris Gibbons and Peter Katic. 5

6 RESULTS Monthly weather summaries for 2012 have been derived from seasonal summaries provided by the Met Office (2012) and were as follows: March It was a very warm and dry month with the mean UK temperature 2.3 C above the average, resulting in the warmest March since 1957 with near record temperatures. There was also very low rainfall making it the driest March since April - It was the coldest April since 1989 with a mean temperature of 0.6 C, below the average. In many areas average rainfall was two or three times the monthly average making it provisionally the wettest April on record across the UK. May - The cool and wet conditions from April continued into the first three weeks of May with temperatures rising only in the last week of the month. June - There was no change in weather conditions during the month with heavy rain and strong winds early in the month, resulting in the wettest June since July - Another cool month with high precipitation with the mean UK temperature 1.0 C below the average and many areas having over twice their average rainfall. August - Further prolonged periods of heavy showers or longer periods of rain continued throughout the month with higher than average rainfall in many areas. September - A notable change in the first half of the month with fine and reasonably warm weather, but it became much cooler with significant rainfall and high winds at the end of the month. October An unsettled month with rainfall and sunshine total close to long-term averages but mean temperatures were 1.3 C below the average, with provisional results suggesting it was the coldest October since Transect Monitoring Results The results of monitoring at Ballowfield in 2012 are shown in Table 1 and Figure 1. The results of monitoring at Lea Green - Bastow Wood in 2012 are shown in Table 2 and figure 2. The results of monitoring at Craven Lime Works in 2012 are shown in Table 3 and Figure 3. The results of monitoring at Scar Close in 2012 are shown in Table 4 and Figure 4. The results of monitoring at Swarth Moor in 2012 are shown in Table 5 and Figure 5. The results of monitoring at Yockenthwaite in 2012 are shown in Table 6 and Figure 6. 6

7 Table 1. The results of transect monitoring at Ballowfield in Week Total Index Weak Index Mean Temp Mean Sun Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Northern Brown Argus Common Blue Small Copper Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Dark Green Fritillary Wall Meadow Brown Ringlet Small Heath Speckled Wood Total

8 Figure 1. Butterflies recorded on the Ballowfield transect in Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Northern Brown Argus Common Blue Small Copper Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Dark Green Fritillary Wall Meadow Brown Ringlet Small Heath Speckled Wood Figure 2. Butterflies and Cistus Forester Moth recorded on the Lea Green-Bastow Wood transect in Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Green Hairstreak Small Copper Northern Brown Argus Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Dark Green Fritillary Speckled Wood Wall Meadow Brown Ringlet Small Heath Cistus Forester 8

9 Table 2. The results of transect monitoring at Lea Green-Bastow Wood in Week Total Index Weak Index Mean Temp Mean Sun Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Green Hairstreak Small Copper Northern Brown Argus Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Dark Green Fritillary Speckled Wood Wall Meadow Brown Ringlet Small Heath Cistus Forester Total

10 Table 3. The results of transect monitoring at Craven Limeworks in Week Weak Index Index Total Mean Temp Mean Sun Small Skipper Large Skipper Brimstone Large White Small White Green-veined White Orange-tip Small Copper Northern Brown Argus Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Dark Green Fritillary Speckled Wood Wall Meadow Brown Ringlet Small Heath Total

11 Figure 3. Butterflies recorded on the Craven Limeworks transect in Small Skipper Large Skipper Brimstone Large White Small White Green-veined White Orange-tip Small Copper Northern Brown Argus Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Dark Green Fritillary Speckled Wood Wall Meadow Brown Ringlet Small Heath Figure 4. Butterflies recorded on the Scar Close transect Small Skipper Large Skipper Clouded Yellow Large White Small White Green-veined White Orange-tip Northern Brown Argus Common Blue Small Copper Red Admiral Painted Lady Small Tortoiseshell Peacock Small Pearl-bordered Dark Green Fritillary Meadow Brown Ringlet Small Heath Wood Tiger Green Hairstreak Silver Y 11

12 Table 4. The results of transect monitoring at Scar Close in 2012 Weak Index Index Total Week Mean Temp Mean Sun Small Skipper Large Skipper Clouded Yellow Large White Small White Green-veined White Orange-tip Northern Brown Argus Common Blue Small Copper Red Admiral Painted Lady Small Tortoiseshell Peacock Small Pearlbordered Fritillary Dark Green Fritillary Meadow Brown Ringlet Small Heath Wood Tiger Green Hairstreak Silver Y Total

13 Table 5. The results of transect monitoring at Swarth Moor in Weak Index Index Total Week Mean Temp Mean Sun Small Skipper Large Skipper Large White Small White Greenveined White Orange-tip Green Hairstreak Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Small Pearlbordered Fritillary Dark Green Fritillary Meadow Brown Ringlet Small Heath Total

14 Figure 5. Butterflies recorded on the Swarth Moor transect in Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Green Hairstreak Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Small Pearl-bordered Dark Green Fritillary Meadow Brown Ringlet Small Heath Gatekeeper Wall Figure 6. Butterflies recorded on the Yockenthwaite transect in Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Green Hairstreak Small Copper Northern Brown Argus Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Speckled Wood Meadow Brown Ringlet Small Heath Dark Green Fritillary 14

15 Table 6. The results of transect monitoring at Yockenthwaite in Week Total Index Weak Index Mean Temp Mean Sun Small Skipper Large Skipper Large White Small White Green-veined White Orange-tip Green Hairstreak Small Copper Northern Brown Argus Common Blue Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Speckled Wood Meadow Brown Ringlet Small Heath Dark Green Fritillary Total

16 DISCUSSION The trends of the priority local BAP butterfly species in 2012 in the YDNP are as follows: Small Pearl-bordered Fritillary There are now only seven Small Pearl-bordered Fritillary sites extant in the Yorkshire Dales National Park and all of these are small (Whitaker 2008; Whitaker, Court & Ellis 2009). Swarth Moor SSSI near Helwith Bridge, Upper Ribblesdale is the largest colony in the YDNP and in 2003 was chosen as a site for a monitoring transect to be set up (Whitaker 2002). A very small population of the butterfly was discovered on the transect set up to monitor the Northern Brown Argus on Scar Close NNR but despite a steadily rising population trend, as indicated by the transect analysis (weak index), it is too small for the trends to be considered significant. The total numbers recorded at Scar Close between 2004 and 2012 are given in table 7. Table 7. Small Pearl-bordered Fritillary on Scar Close NNR. YEAR TOTAL On Swarth Moor, if the period between 2004 and 2006 when the summers were particularly benign are excluded, the Small Pearl-bordered Fritillary population appears to be stable (as shown in figure 7). Figure 7. The population index of Small Pearl-bordered Fritillary on Swarth Moor between 2003 and

17 Northern Brown Argus The Northern Brown Argus is found on three of the transect sites in the YDNP: Bastow Wood in Upper Wharfedale, Scar Close NNR on the northwest slopes of Ingleborough and Ballowfield in upper Wensleydale, and the was formerly present at Yockenthwaite in Langstrothdale. The Northern Brown Argus transect at Threshfield (Long Ashes) was not walked in 2012 and will probably be abandoned. The flight season and recording in 2012 was badly affected by the poor and changeable summer weather, especially at the sites where the species flies late in the season. No Northern Brown Argus were recorded at Ballowfield or Yockenthwaite. At Lee Green, good numbers were recorded in 2012 and the weak index between 2006 and 2012 shows that the population was still increasing slightly. At Scar Close, a high altitude site that is relatively exposed, the observation of the species is greatly influenced by the weather with the trends creating large variability in the data the long term population trend is a decline. The overall combined population trend for Northern Brown Argus in the YDNP between 2004 and 2011 is shown in figure 8 but there are insufficient transects to derive a definitive trend. Figure 8. The population trend of Northern Brown Argus in the Yorkshire Dales National Park between 2004 and Population Indices Dales UK Small Heath The Small Heath is recorded on all the six of the Yorkshire Dales transects. Of the sites with extended data, three have a weak index that shows an increasing population trend but two show a declining trend. The combined trend for the YDNP is shown in figure 9 and shows that the population is increasing. 17

18 Figure 9. The population trend of Small Heath in the Yorkshire Dales National Park between 2004 and Population Indices Dales UK ACKNOWLEDGEMENTS The authors would like to thank all the individuals who have contributed to the transect survey work. We would also like to thank Dave Wainwright for his continued advice and support and Ian Middlebrook at Butterfly Conservation for undertaking the trend analysis for Small Heath and Northern Brown Argus population in the YDNP. 18

19 REFERENCES Biological Records Centre Methods for recording butterfly transects. Accessed 7 March Court, I.R. and Whitaker, T. M The status of Small Pearl-bordered Fritillary Boloria selene Butterfly in the Yorkshire Dales National Park. Yorkshire Dales National Park Authority Conservation Research & Monitoring Report No. 10. Grassington. Met Office UK Climate. Accessed 1 Nov Pollard, E. and Yates, T.J Monitoring butterflies for ecology and conservation. Chapman & Hall, London. Whitaker, T. M unpubl. Boloria selene (Denis & Schiffermüller) (Lepidoptera, Nymphalidae) The Small Pearl-bordered Fritillary in the Yorkshire Dales National Park. Private report to the YDNPA (Ref. No. 3802/A400/ Project A4Ecol) & English Nature, Biodiversity Grant Scheme (Ref. Number 03/BGNT/211), 36pp + maps. Whitaker, T. M Population Estimates & Relationship to Population Indices in the Dark Green Fritillary (Argynnis aglaja L.) at Scar Close NNR, Ingleborough Internal report to the Yorkshire Dales National Park Authority and Butterfly Conservation. Grassington. Whitaker, T. M unpubl. The Small Pearl-Bordered Fritillary Boloria Selene in the Yorkshire Dales National Park, Craven outside the YDNP & adjacent areas. Final Report Private report to the YDNPA, Grassington (Ref. No. S0176/PO003955) & to Butterfly Conservation, East Lulworth (Ref. No. R30/PQU689), 30pp. Whitaker, T.M., Court, I.R. & Ellis, S. (2009). Status of Northern Brown Argus Aricia artaxerxes & Small Pearl-bordered Fritillary Boloria selene in the Yorkshire Dales National Park Naturalist 134 (1069):

20 Appendix 1. G1: Monitoring butterfly numbers by the transect method summary information for recorders. 20

21 Appendix 2. G2: Field guidance notes for butterfly conservation published by Butterfly Conservation %20notes.pdf 21

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