BLACKDOWN HILLS 2013 BIG BAT SURVEY

Transcription

1 BLACKDOWN HILLS 2013 BIG BAT SURVEY 1

2 Summary The third Blackdown Hills Big Bat Survey was run by the Somerset Environmental Records Centre (SERC) with the help and support of the Somerset Bat Group (SBG) and the Blackdown Hills Area of Outstanding Natural Beauty Partnership (Blackdown Hills AONB). It was made possible with the generous financial support of the Blackdown Hills AONB through their Sustainable Development Fund. Without these three bodies it would not have been possible. Equally, the whole survey depended on the enthusiasm and expertise of an army of volunteers giving their time to design and walk transects, stumble about in the dark and spend hours at a computer analysing the results. In contrast with the two previous years, there was a large number of passes from small bats (Pipistrelles and Myotis species) recorded in quite open and exposed countryside. The still conditions probably allowed insects to fly well clear of tree cover and their predators followed them out onto the heaths and pastures. The three big bat species (Noctule, Serotine and Leislers Bat) were all recorded but there were fewer passes from them than in Bigger bats can, of course, fly further to find their food than the small ones and it is therefore even more likely that they will not be in the same place every year. The transects design was the work of Cath Shellswell, Lou Pickersgill, Liz Biron and Edward and Helen Wells. The administration and organisation of the survey was carried out by Charlotte Johns, SERC Ecologist. The analysis of recordings was carried out by the authors of this report. Acknowledgements Special thanks to All the volunteers that took part in the surveys: Brian Ahern, Pete Banfield, Conrad Barrowclough, Lucy Bartlett, Linda Bennett, Nick Bentley, Liz Biron, David Blake, Natalie Boote, Simon Peter Briggs, Ros Buckley, Sarah Butcher, Dave Cottle, Chris Couzeks, Jeremy, Kathleen and Tim Cuff, John Daw, Martin and Angela Drake, Harry Fox, John and Valerie Godsmark, Kiff and Ruth Hancock, Kevin Harris, Rob Harrison, David Izzard, Beth Jerrett, Sue Jones, Paul Kennedy, Monique Kors, Chris Lampshire, Philip Lewenz, Philippa Lidyard, David Lloyd, James Locke, Gillian Lowe, Matthew Marshall, Will Molyneaux, Hannah Montag, Daphine Morris, Lila Morris, Jenny Patton, Tim Pitcher, Ed Redgrove, Adam Robbins, Eloise Robinson, Michael Robinson, Andrew Ross, Tony Serjeant, Cath Shellswell, Suzanne Ubink, William and Emma Wake, Edward and Helen Wells, Vernon and Sheila Whitlock Honiton, Martin Wolinski and Lucy Wood. All the land holders that allowed the survey to take place around their holding. All of the people that gave comments on the text of this report. Cover photograph: Daubentons Bat captured at Hawkridge Reservoir in 2010 Paul Kennedy Report Authors: Edward Wells and Cath Shellswell of Somerset Bat Group 2

3 1. INTRODUCTION Whilst a number of specific bat roosts within the Blackdown Hills AONB have been known for many years, the way in which bats use the landscape of this interesting and varied part of Somerset and Devon has been only sparsely studied. Flight records have been largely anecdotal. Accordingly the AONB commissioned SERC to carry out a Batscapes study using aerial photograph interpretation and the Integrated Habitats System (IHS) to map and predict areas likely to be suitable for the various British bat species. This work produced predictive maps for a number of species based on their known habitat requirements and on the distribution of known records. There are 17 species of bat known to breed in Britain and 16 of those are recorded in Somerset. A survey for the National Bat Monitoring Programme of the Bat Conservation Trust in 2010 and 2011 revealed a number of sites for the nationally rare Bechsteins Bat (Myotis bechsteinii) in and near the Blackdown Hills. In addition, droppings analysed from a roost near the Blackdown Hills have recently proved to be Grey Long-eared Bat indicating that this species may also be present within the AONB. Clearly the area could be of great importance for bats. It was in this context that in addition to other surveys SERC agreed in 2011 to set up the Blackdown Hills Big Bat Survey following the model of the highly successful Mendip Hills Big Bat Survey. This not only provides a significant body of data of bat activity in the form of flight records but also encourages local people to find the bats with SERC and enjoy a largely hidden element of their local wildlife at the side of experienced bat workers. The first survey in July 2011 attracted some 63 volunteers; the second survey involved 70 volunteers enabling an additional four new routes to be included during In 2013 even more routes were added bringing the total up to 16. It was felt that the original set of routes rather neglected that part of the Blackdown Hills AONB that was in Devon so the additional routes were all in East Devon. A total of 62 volunteers took part. As bats are highly mobile, their presence is a good indicator of the status of habitats and they can be used to monitor changes in the condition of the wider landscape. For example, Intensive land management can deplete the invertebrate population and bats will move elsewhere. The data acquired by the Mendip Big Bat Survey has already been used to support agri-environment agreements and wider landscape management. The way that the different bat species use the environment, particularly in relation to the use of linear landscape features to commute and feed opportunistically, is still a matter of research and debate but it can only help inform that debate to have comparative data covering a number of years showing where in the landscape bats are encountered. The Blackdown Hills represent an outstanding area in which to collect such data with their un-intensive land use and varied mosaic of habitats supported through high nature value farming and forestry. Public paths were an essential part of the transect route and public roads were avoided wherever possible. It was essential that the route prescribed should be safe and able to be negotiated within a reasonable time. It was equally essential that the surveying did not disturb or put at risk any landowners, their livestock or their crops. The methods used in this survey, whilst providing robust and meaningful data, also provides an opportunity for a large number of people to experience the pleasure of listening for bats. Local naturalists have discovered a whole new world in their own neighbourhood, a world which only comes to life when the sun has gone down. Sixteen transects were surveyed on 19th of July The volunteers were divided between those transects so that no team was less than four people. Heterodyne bat detectors were supplied to those who did not have their own. Before the survey took place Edward Wells ran a workshop on the 28 th June 2013 to help inexperienced volunteers get some idea of how to interpret what they were likely to hear on such a detector. It is unlikely that bats associate the noises from detectors with their own sounds, and they show no sign of being affected. Groups of 4 or 5 people walking the transects represent only a very slight and transient intrusion. Much of the purpose of repeating a survey of this kind over a number of years is to try to iron out inconsistencies caused by variable factors such as weather and farming practice. The 2013 survey night was warm with temperatures in some areas of over 20 degrees. It was also very still with no discernible wind. This was a significant difference from the 2012 survey which was cooler and noticeably breezy. Unlike the 2011 survey however the evening was dry. At least another year and ideally another 3 years are envisaged to get enough information to produce statistically robust results. 3

4 2. METHOD The 2013 Blackdowns Big Bat Survey is a landscape survey to collect comparable data across the Area of Outstanding Natural Beauty: (a) 16 predetermined routes (figure 1) were walked simultaneously comprising a series of six walking sections and six stationary points. Each team of volunteers listened to bats using heterodyne, time expansion or frequency division bat detectors and listed what they heard in each section. (b) At the same time one person in each group undertook a continuous recording on a wave recorder using a frequency division Batbox Duet bat detector. The recordings were assigned to separate tracks for each section and then analysed to count the number of bat passes in each section and, so far as possible, assign those passes to species Survey Sixteen transects were surveyed (Figure 1). All were completed and good frequency division sound data was collected from each route. Each walk consisted of six stops of 5 minutes and six walked sections lasting an average of about 10 minutes. The stops were chosen strategically where there were potentially significant landscape features and the walks were mainly along established footpaths for the comfort and safety of the volunteers. Each transect was walked in their normal configuration (2012 was a reverse route year to record the transect back-to-front in case of differences in bat activity depending on the time of evening). For clarity in comparing years, on the maps and tables of this report the numbering of stops and walks has been shown the same for all years and a note has been made for 2012 when the survey was walked in reverse. To create each route, a walk was drafted using OS Explorer Map 115, 116 and 128. The transect was subsequently checked to measure the timings of the sections at a steady walking pace and define the different habitats at the stops. The volunteers were provided with maps of the transect they were undertaking, a risk assessment and asked to walk the route in daylight for safety prior to the survey. All landowners along each transect were asked for permission to access their land and none denied permission. Further information that was provided to volunteers is available from the Somerset Environmental Records Centre. Before starting the surveys, the volunteers met for a brief health and safety talk and then travelled to the beginning of each transect. 4-6 individuals with a mixture of bat experience from beginner to very experienced were assigned to each group. The surveys started at 21:30 and finished at approximately 23:30. A chosen volunteer in each group, usually the group leader that was recording the transect, returned to the Village Hall in Bishopswood to report that they had completed the transect in safety and to hand-in the recordings and survey forms. 2.2 Sound Analysis Each transect s recordings were analysed using BatSound software. The number of bat passes made by each species or group was counted to provide a measure of bat activity along each walk section and stop section. A bat pass is a continuous stream of echolocation calls indicating a bat flying past. The number of bat passes is therefore best understood as an index of bat activity rather than the absolute number of bats in the area. Except for the bats of the genera Myotis and Plecotus (long-eared bats), each species has a spectrogram which is usually sufficiently distinctive. 2.3 Limitations of the Survey There are several factors that may affect the results and comparison between the routes: Differences in the range of individual bat detectors individual detectors of the same type can vary in range depending on factors such as local environmental conditions and battery strength. Changes in environmental conditions such as weather can be compensated by carrying out the surveys at the same time on the same night, and new batteries can be used. Observer error misidentifying bat passes and counting the number of bat passes the standard procedure for counting bat passes was followed; however there is scope for error if more than one bat of the same species / genus is passing the bat detector at one time. There is also the potential to misidentify species, particularly if the call is faint. Human error the bat passes for Transects 5 (Otterhead Lakes) and 8 (Dunkeswell) were not recorded in frequency division but in heterodyne. Equipment failure there were cases of passes heard by the surveyors that were not recorded due to the need to replace batteries and in that situation we have relied on the written notes. There is a lower level

5 of confidence in the identification of the species missed in this way but given the experience of the recorders concerned we considered it appropriate to accept their identification even though it could not be subjected to objective verification by sound analysis. There is a greater danger of inaccuracies in identifying species from bat passes from heterodyne recordings, and individual bat passes are more difficult to distinguish if more than one bat is flying past the bat detector at the same time resulting in counting errors. Faint recordings - occasionally the echolocation on the recording was too faint to identify the bat species. Faint recordings also make it difficult to extract a peak frequency for the echolocation calls of pipistrelle species. Where the genus of bat was uncertain the recording is marked in the report as unknown bat species and where there is sufficient confidence to assign a recording to the genus Pipistrellus but not to a species the recording is marked as Pipistrelle sp. Figure 1: Map of the bat transects undertaken as part of the Blackdowns Big Bat Survey 3. RESULTS AND SOUND ANALYSIS 3.1 Overall summary As in 2011 and 2012 the most frequently recorded bat species was the Common 45 khz Pipistrelle. This species represented 61.7% of all bat passes recorded (Table 1). Myotis sp and Soprano 55 khz Pipistrelles were recorded the second most frequently (12.7% and 12.2% respectively). One interesting contrast with the two previous years was the significant number of passes from small bats (Pipistrelles and Myotis species) recorded in quite open and exposed countryside. The still conditions probably allowed insects to fly well clear of tree cover and their predators followed them out onto the heaths. The three big bat species (Noctule, Serotine and Leislers Bat) were all recorded in similar quantities to 2011 and far greater than in 2012 which had very adverse weather conditions. Bigger bats can, of course, fly further to find their food than the small ones and it is therefore even more likely that they will not be in the same place every year. Long-eared bats are generally difficult to record due to their tendency to use passive hearing to catch prey rather than 5

6 echolocation and no passes were recorded in 2013 from these two species. The more obvious contrasts will be highlighted in the notes on each transect but it is still far too early to draw any firm conclusions from the data. Table 1 shows the number of bat passes and proportion of total calls for all the species recorded, and the following maps show the cumulative presence of species recorded across the Blackdown Hills. The results only show presence of bats identified from the recordings and can not indicate the absence of a particular species as the survey does not cover the entirety of each square kilometre, and, consequently, there is the possibility that species may have been missed. The addition of four new transects in 2012 means that the results between 2011 and are not a direct comparison. Table 1: Number and proportion of bat passes recorded for each species / group results should not be directly compared to 2012 and 2013 as it contains four fewer transects Species /Species Group 2011 Bat Passes 2011 Total (%) 2012 Bat Passes 2012 Total (%) 2013 bat Passes 2013 Total (%) Lesser horseshoe Common 45 pipistrelle Soprano 55 pipistrelle Pipistrelle sp Serotine Noctule Leisler s <0.1 Myotis sp Long-eared Bat Barbastelle Unidentified bat species TOTAL

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10 3.2 Bat passes recorded along each transect route The recordings from each transect were analysed separately and divided into the walk and stop sections shown in the following tables and maps. It is, of course, impossible to draw any conclusions from three sets of data and the following observations must be treated with caution and can at best merely highlight possible areas of comparison for next year and the ensuing years. 10

11 3.2.1 Transect 1: Buckland Wood and Quants Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Myotis sp Unidentified bat passes * Lesser Horseshoe Pipistrelle Myotis sp Unidentified bat passes Lesser Horseshoe Pipistrelle Pipistrelle 1 1 Myotis sp Serotine 5 5 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. Unfortunately there was an issue with the recording on the 2013 survey. A wire had become disconnected in the lead between the bat detector and recorder, which caused the recording to be skipped, gradually becoming worse from Walk 3 onwards. Walk 6 is almost entirely taken from the survey form filled in by the group. This is an excellent example where the survey form was incredibly useful to decipher results which would otherwise have been missed. The five Serotine passes at Stop 2 are of note as this is not a section which would appear to be typical Serotine habitat. It is however a large and very mobile species. The large number of Common Pipistrelle passes at Walk 2 is notable although it may be the results of a few very active individuals. As in 2012 there is a Lesser Horseshoe Bat recorded suggesting a summer roost somewhere nearby. 11

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13 3.2.2 Transect 2: Sampford and Black Down Commons Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Myotis spp Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle sp Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. As noted in the 2012 report, most of this transect is higher than 250m above sea level, the ends of the route follow tree-lined lanes and hedges whilst the centre of the route is particularly exposed on the open common. The evening was very warm and still which may have enabled bats to find food and hunt out on the open moorland recorded between Walk 3 and Stop 4. The lack of big bats in 2012 and 2013 is a little surprising as the habitat is of a kind often associated with Noctules and Barbastelles. If such species do use the moor it may be that they do so later in the night, and there are observations from Blackdown Common on the Mendip Hills, a fairly similar acid grassland bracken lowland heathland mosaic that bats may use the open areas during the small hours of the night. It may also be possible that mass hatchings of specific prey insects might make these open areas more favourable at specific times of the year (depending on the weather and 2013 was a delayed summer due to a lengthy cold period during April delaying plant growth) or at specific times of the night. What is quite clear is that if the weather is suitable open land is as good for bat activity as woodland. The table above is from the recordings made by the transect team leader but another volunteer walking this transect also recorded using the same equipment and methodology. This provides an interesting comparison. Some passes recorded by one detector were missed by the other but that is entirely to be expected as the two were some yards apart and not necessarily pointing in the same direction. For comparison the results of the second set of recordings is shown below. Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Unidentified bat passes

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15 3.2.3 Transect 3: Bolham Water Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis spp Serotine 5 5 Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. This transect continues to show a great deal of Pipistrelle activity in the second half of the circuit although nothing quite like the quantity of passes in the previous two years. Conversely the small bridge over the stream at Stop 2 which always looked as though it ought to be good for Daubentons Bats lived up to its promise. Stop 4, which also had a number of Myotis passes in both 2012 and 2013, is at a larger bridge further along the same watercourse. Although as usual Myotis bats were not identified to species level there is a very strong probability that most or all of these passes were of Daubentons Bat. 15

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17 3.2.4 Transect 4: Castle Neroche Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Barbastelle Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine 2 2 Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Barbastelle Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. This transect was lead in the first two years by the late Lou Pickersgill, Somerset s authority on finding Barbastelles. She would have been pleased to see 10 passes from this elusive species at Stop 3 not least because having been detected in 2011 none were picked up last year. The Neroche Forest is almost perfect foraging habitat for this species. The Lesser Horseshoe Bat which was found at Stop 6 in both the last two years was not heard this time but that does not mean it was not there as the high pitched echolocation calls only cover a very short distance and the bat may have been just out of range. This transect continues to deliver plenty of Common Pipistrelle activity and a great deal less sign of Soprano Pipistrelles in 2013 compared with That is consistent with the theory that the later species is more associated with water, one habitat element that is lacking at Castle Neroche. 17

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19 3.2.5 Transect 5: Otterford Lakes Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis spp Noctule Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis sp Serotine Long-eared bat sp 1 1 Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 2 2 Myotis sp Noctule 1 1 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. A problem with the recording along this transect meant that only the written form and heterodyne recordings were available. That has almost certainly reduced the totals recorded significantly especially in relation to non-pipistrelle species. The high number of unidentified bat passes is a product of not being able to analyse the recordings in the way that frequency division recordings can be scrutinised. Even with this recording issue, the lack of activity at Stop 2 is very surprising and it will be interesting to undertake this survey again as bat activity was very busy at this location in 2012 when the weather conditions were not as favourable and the route was walked in reverse. Stop 2 is over-looking a large body of water and has over many decades been a reliable place to observe Daubentons Bats, Pipistrelles and Noctules. The later part of the transect, which is largely along a road past coniferous plantations, seems to have been quite busy this year. 19

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21 3.2.6 Transect 6: Staple Hill Plantations Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Myotis spp Serotine Unidentified bat passes * Lesser Horseshoe Pipistrelle Myotis spp Unidentified bat passes Pipistrelle Pipistrelle 4 4 Myotis sp Serotine 4 4 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. This is another exposed transect and quite high up. As with Transect 1 the still air seems to have worked to the bats advantage with more passes than in either of the previous two years. Given that the transect was walked in reverse in 2012 the consistent hot spot for Common Pipistrelles at Walk 6 may be a genuinely preferred hunting ground. The results for 2011 and 2013 look quite similar and 2014 may start to show whether that is a feature of the direction of travel (i.e. the time at which each point is reached) or the result of warmer weather and more insects on the high ground. 21

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23 3.2.7 Transect 7: Thurlbear Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Noctule Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle This portion of the survey was Pipistrelle sp 1 1 missed in 2012 Myotis sp Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine Noctule * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. The big bats that were absent from the recordings in 2012 were back in It is possible that this may reflect the lack of grazing during the wet summer of 2012 but it is encouraging that Serotines were recorded in four of the twelve sections. Noctules were present as well. It is harder to explain why Soprano Pipistrelles, which only contributed nine passes in 2011 and 2012 combined, produced a total of 29 passes this year. It could be due to a few individual bats at Stop 1 flying towards Walk 2 increased the number of Soprano Pipistrelle passes, but the calls seemed to be more spread out than this presented scenario. It will be interesting to see if there are any Soprano Pipistrelle passes in significant numbers in

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25 3.2.8 Transect 8: Dunkeswell Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle 3 3 Myotis spp Noctule 2 2 Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Myotis spp Noctule 1 1 Long-eared Bat sp Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Noctule 1 1 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. There was a problem with the recording along this transect and only the heterodyne signals and the written form were available to analyse. This means that a number of bats, though probably not many Pipistrelles may have been missed and identification of bats as Myotis or Pipistrelle should be given a lower confidence level. The same applies to assigning calls to the two different common Pipistrelle species. None the less the table above is the best that can be produced within those caveats. Although the overall figures are lower, the proportions of the different species are quite like those in If a further survey is undertaken on a warm evening, it should be possible to tell whether the differences in 2011 were a feature of conditions or a result of walking the transect in reverse. 25

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27 3.2.9 Transect 9: Yarcombe Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle 3 3 Myotis sp Serotine Barbastelle Unidentified bat passes * 45 Pipistrelle Myotis sp Serotine 3 3 Unidentified bat passes Pipistrelle Pipistrelle Myotis sp Serotine Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. Although this transect was properly recorded in frequency division the recording level was very high and the resultant noise made identification a little difficult. This is reflected in the high number of unidentified bat passes. Also present is another case of an increase in Soprano Pipistrelle activity. During the Mendip Hills Big Bat Survey, there was one year in which there was a sudden increase of this species and we may be seeing the same thing in the Blackdown Hills. The Barbastelles which were such a feature of this transect in 2011 did not appear, but Serotines have remained consistent from year to year. 27

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29 Transect 10: Membury Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis spp Noctule Leisler s 5 5 Serotine Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine Noctule Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. Although Common Pipistrelle activity was lower, this transect seems remarkably consistent both in the species recorded along the route and in their position on the walk. Walk 3 to Walk 4 has continuously been good for Pipistrelles. The outstanding feature this year is the Serotine passes, far higher than anywhere else in the survey thanks to an extraordinary 33 passes at Stop 2. Since this was a stop rather than a walk it suggests that the detector was placed right where one or more Serotines were feeding it is an excellent total. 29

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31 Transect 11: Wambrook Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 Lesser Horseshoe Pipistrelle Pipistrelle Myotis sp Noctule 1 1 Serotine Brown Long-eared Bat 3 3 Unidentified bat passes * Lesser Horseshoe Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Unidentified bat passes Lesser Horseshoe Pipistrelle Pipistrelle 1 1 Myotis sp Serotine 1 1 Leislers 1 1 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. The question posed in the 2012 report was whether an absence of passes in Walk 1 was a result of the reversal of the direction in which the transect was walked. As there were no passes at this point again in 2013 it would appear not. Numbers of passes generally were down on the previous two years and it is interesting to note that the Lesser Horseshoe Bat passes recorded at Walk 6 and Stop 6 in 2011 and 2012 were not recorded this time. Two Lesser Horseshoe Bat passes were recorded from this species at Stop 2 almost as far away from the known maternity roost as the transect goes. Even small bats can clearly cover quite a distance soon after emergence. 31

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33 Transect 12: White Staunton Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total Pipistrelle Pipistrelle Myotis sp Noctule 2 2 Serotine Unidentified bat passes * 45 Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp Serotine Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 4 4 Myotis sp Serotine Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. The results from the first section of this transect, Walk 1, should to be treated with some caution. There was a deviation from the prescribed route and whilst the first two passes, both of Common Pipistrelles, were on the route the remainder may not have been. The results of the entire sections recording is shown in spite of this caveat. Unusually, this transect recorded markedly fewer passes in 2013 and 2011 than in the difficult summer of 2012, although the route was reversed during the middle year which may account for some change in activity. The areas in which the bats were recorded were fairly consistent from year to year except in the case of the few Myotis bats which were previously noted in the second half of the transect but not this time. In all years, the route between Stop 2 and Stop 4 less activity than the ends of the ends of the routes, and this part of the transect appears to pass through fairly open farmland. 33

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35 Transect 13: Broadhembury Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine 2 2 Unidentified bat passes Pipistrelle Pipistrelle 1 1 Myotis sp Serotine Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. Some problems were encountered with this transect. Only a small part of Walk 3 and Stop 4 recorded properly and the number of passes for Walk 3 is taken from the written form. A Myotis sp pass was recorded at Stop 5 as having been heard but not recorded and this pass is also included. As with Transect 12 the numbers are very much lower in 2013 with all Pipistrelles recorded at only 29% of their 2012 level. The activity seems in both years to be concentrated on the lower parts of the route as one might expect but it is always possible that the bats are going further afield in better conditions and spreading out further. Clearly two years of data are not enough to start to make any assumptions, especially with only one route change in direction. 35

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37 Transect 14: Upottery Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle Pipistrelle sp Myotis sp Serotine Barbastelle 2 2 Long-eared Bat 1 1 Unidentified bat passes Pipistrelle Pipistrelle Pipistrelle sp 1 1 Myotis sp 1 1 Serotine Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. In 2012 this transect was the richest route in terms of bat passes, but this has not continued in Pipistrelle passes were less than a quarter of their total the previous year. Myotis bat passes were down to 1 from an encouraging 26 and Serotine to 2 from 32. The Barbastelle was not recorded again this year. Next year s results will be particularly interesting to see if the dip in bat activity continues or whether the situation reverses along with a reverse in route direction. The weather may have also played a role in the change in activity and perhaps the bats were seeking good foraging habitat away from exposed locations in 2012, such as the path between Walk 1 and Stop 2 and woodland edge at Stop 4 during the inclement weather of that year, whilst there were better foraging locations available elsewhere in It is, of course, worth remembering that bat passes do not equate to the number of bats present and a continuous pass lasting some minutes will still only be recorded as one pass. 37

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39 Transect 15: Cotleigh Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle 3 3 Myotis spp Serotine Pipistrelle Pipistrelle 1 1 Myotis sp Serotine 1 1 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. In the 2012 report we expressed some mystification at the low level of activity in what looked like ideal habitat s data are much more what one would expect. The Myotis passes recorded were very similar but the Pipistrelles were much more active. Walk 2 to Walk 4 seems to be the best part of the route for bat passes and Walk and Stop 1 the quietest part of the route. 39

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41 Transect 16: Netherclay Year Bat Species Transect Section Walk 1 Stop 1 Walk 2 Stop 2 Walk 3 Stop 3 Walk 4 Stop 4 Walk 5 Stop 5 Walk 6 Stop 6 Total 2011 This transect was not undertaken in * 45 Pipistrelle Pipistrelle Myotis spp Noctule 1 1 Unidentified bat passes Pipistrelle Pipistrelle Myotis sp Serotine Noctule 1 1 Unidentified bat passes * The 2012 survey was completed in reverse starting at Stop 6 and finishing at Walk 1. The number of Pipistrelle passes are virtually identical for the two years of survey, but Serotines, which were not recorded in 2012, are present in good numbers over the middle part of the transect. At the same time Myotis passes have gone down from 147 to 12. The absence of Serotines in 2012 may be related to the disruption of grazing during the wet summer and 2013 may prove to be a more typical year. It is possible that Myotis bats may avoid direct competition with the much larger Serotines, but we are not aware of any firm evidence that the two genera interact negatively. Next year the pattern may well be different again as the transect swaps round to the other direction or depending on weather conditions. 41

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