Appendix 1: Bat detector surveys in Greater Stockgrove in 2015

Transcription

1 Appendix 1: Bat detector surveys in Greater Stockgrove in 15 Bat detector walking surveys and static recordings in 15. (KW = King s Wood) Date Area Duration / min Bat passes 1 Bat passes per hour Species recorded th April Stockgrove Lake SP, CP, Noc, Leis, Daub th April Baker s Wood SP, Noc, Myotis sp., Barb 7 th April Stockgrove SP, CP, Noc, Leis, Daub th April Stockgrove Lake SP, CP, Noc, Daub, Natt th April Baker s Wood, Shire Oak Heath & Stockgrove SP, Noc 7 th May Oak Wood SP, CP, Noc, Nyctalus sp., big bat, Myotis sp., BLE, Barb 7 th May Black Pond (static) SP, CP, Noc, Nyctalus sp., Ser, big bat, Natt?, Myotis sp. nd June Baker s Wood SP, CP, Nyctalus sp., Ser, Myotis sp. 1 th June Northwest KW (static) 7-15 th June Southern KW SP, CP, Myotis sp., BLE, Barb 15 th June Baker s Wood (static) 5 1. SP 18 th June Brickhill Rd to Rammamere Heath SP, CP, Myotis sp., Natt? 18 th June Brickhill Rd (static) CP 18 th June Brickhill Rd (static) SP, CP, Ser?, Barb 4 th June Leaf seats area (static) Myotis sp. 4 th June Leaf seats area (static) 7 9. SP, Myotis sp., Barb 4 th June Leaf Seats area SP, CP, Noc, Nyctalus sp., Barb th June near Leaf seats (static) 7 - th June Leaf seats area SP, CP, Noc, Natt, Myotis sp. 9 th June Stockgrove Bottom (static) CP, Noc, Myotis sp. 9 th June Stockgrove Bottom SP, CP, Noc, Nyctalus sp., Ser, Myotis sp., Barb 3 th June Rushmere sheds (static) SP, CP, Noc (Myotis sp. heard) 3 th June Rushmere main drive SP, CP, Noc, Natt, Myotis sp., Barb 3 th June Rushmere Lake (static) SP, CP, NP?, Leis?, Daub, Myotis sp., 3 rd July Big Pond KW (static) Noc, unidentified 3 rd July North and main ride KW SP, CP, Noc, Myotis sp., Barb th July South end of main ride KW (static) 58 - th July Southern edge KW SP, CP, Noc, Myotis sp., Barb 8 th July Grounds of The Grange SP, CP, Ser?, BLE 8 th July The Grange (static) SP, CP, Ser?, Myotis sp. 13 th July 15 th July Western edge KW + Bragenham Wood Lower valley (near Main Drive) (static) SP SP, CP, Noc, Nyctalus sp., Myotis sp., BLE?, Barb 15 th July Rushmere Main Drive SP, CP, Nath Pip, Noc, Myotis sp., Barb 7 th July Stockgrove SP, CP, Noc, Nyctalus sp., big bat, Myotis sp., BLE 4 th August SE Rushmere (static) SP, CP, Natt, Myotis sp. 4 th August SE Rushmere SP, CP, Noc, big bat, Natt, Myotis sp., BLE, Barb 4 th Sept Oakwood Cotts. (static) SP, CP, Noc, Nyctalus sp., Myotis sp., BLE, Barb 4 th Sept The Grange (static) SP, CP, Natt SP= Soprano Pipistrelle; CP= Common Pipistrelle; Nath Pi = Nathusius Pipistrelle; No = Noctule; Leis= Leisler s Bat; Ser= Serotine; Natt = Natterer s Bat; Daub = Daubenton s Bat; BLE = Brown Long-Eared Bat; Barb= Barbastelle; big bat= Noctule, Leisler s Bat or Serotine.

2 Ba passes recorded per hour Number of species recorded Appendix : Evaluation of Methods Bat detector surveys Detector surveys were of three types, all involving recording for later sonogram analysis to determine species. Some static surveys were carried out at convenient locations using an Echometer Touch and ipad, while others were carried out at selected locations using a Batbox Griffin. Roving detector surveys also used a Batbox Griffin. In ten cases, static and roving Griffin surveys took place simultaneously in the same general area. Analysis of Griffin recordings enabled quantitative comparisons to be made. The average duration of roving and static surveys was similar, but there was more variation in the static surveys (from 31 to 13 minutes) than in the roving surveys (from 47 to 9 minutes). Levels of bat activity varied enormously between surveys, but it was noticeable that roving surveys recorded both higher levels of bat activity (expressed as the number of bat passes per hour) and a greater diversity of bats (expressed conservatively as the number of bat species which could be clearly identified as different). The 15 surveys using the Echometer Touch did not lend themselves to similar analysis because they tended not to record in a continuous way and they are not comparable the Batbox Griffin in sensitivity or mode of triggering. Comparison of roving and static detector surveys using a Batbox Griffin Roving Static Number of surveys 17 1 Median duration/min Minimum bat passes/h 11.5 Maximum bat passes/h Median bat passes/h Median no. of bat species 5 The variation between survey areas, assessment of which was the primary aim of carrying out the surveys, tended to mask differences resulting from the two modes of using the BatBox Griffin (roving and static). However, in the ten pairs of recordings which can be matched, the static and roving recordings were made on the same nights, at approximately the same times and in approximately the same areas. It is therefore possible to compare each pair of recordings in order to make some evaluation of the two methods. Because the surveys were not planned for the purpose of this evaluation, there were some differences in methodology which need to be borne in mind. In particular, the lengths of the surveys were not always matched. In seven out of the ten pairs, the durations differed by 5% or less but in the remaining three cases the difference was much greater. Two of the roving surveys were more than twice as long as the matched static surveys. Three static surveys were longer than the corresponding roving surveys, but six were shorter and one was almost exactly the same length. 3 5 Roving Static 7 Roving Static In every one of the matched pairs of surveys the number of bat passes per hour was greater in the roving survey than in the static survey. This is a significant difference (Wilcoxon test for matched pairs, two tailed, p =.). The number of species was never greater in the static survey than in the corresponding roving survey and was smaller in eight out of the ten pairs. This, too, was significant (Wilcoxon test for matched pairs, two tailed, p <.). The most likely explanation is that the roving surveys have a much greater chance of encountering bats because they cover more ground. Static surveys have a lower chance of detecting bats unless they happen to have been sited in a bat hot spot. This is relatively unlikely except where the choice of location was informed by prior information (as it was in the case of Oak Wood) and even then a hot spot for some species will not necessarily be a hot spot for others. It is interesting that when two static surveys were carried out simultaneously in the Leaf Seats area (not included in the matched pairs because there was no corresponding roving survey on

3 Bats caught per hour the same night), one recorded much more bat activity than the other. A roving survey would have taken in both locations and many others in addition. The difference in the number of species could be related to differing durations of surveys: it is noticeable that in the two cases where the number of species recorded was the same, the static survey was either the same duration as the roving survey or, in the case of Oak Wood, was significantly longer. It seems much less likely that the frequency of bat passes is caused purely by the differing durations of the surveys. Nonetheless, static surveys have their value because they can help to identify significant locations, and they have the advantage that they are unattended and can therefore be done while other survey work (e.g. trapping) is taking place. Trapping methods A benefit of relatively large scale trapping as was carried out in Greater Stockgrove in 15 is that the number of captures is large enough to look for some significant patterns in results. The BatMap weekend involved trapping from sunset (approximately :3 BST) until some time between : and 3:. Time of night: Analysis of the total Breakdown of bats caught at time periods during BatMap numbers of bats caught during the First hour To midnight After midnight three time periods reveals that Approx duration: 1 hour.5 hours.5 hours Total 8 during the first hour after sunset Common Pip (. bats/hr) and the period Noctule between this time and midnight capture rates were very similar Soprano Pip 1 (3.8 bats/hr). After midnight, the capture rate fell to about half of the earlier rate (14. bats/hr.). The pattern is significant (Χ = 1., degrees of freedom, p<.1). When the data are examined species by species (graph below), the drop in Natterer s Daubenton s Brandt s Whiskered Brown L-Eared Barbastelle Total captures after midnight is evident Note: The Myotis caught by the Crossroads team is excluded in every case. A comparison between capture rates in the first hour and between 1:3 and midnight reveals three apparent patterns. Captures were greater between 1:3 and midnight in Brown Long-Eared Bats (Exact Binomial Goodness-of-Fit Test, two-tailed, p=.5) and in Common Pipistrelles, none of which were caught in the first hour (Exact Binomial Goodness-of-Fit Test, two-tailed, p=.). Daubenton s Bats, Natterer s Bats and Barbastelles showed a higher capture rate in the first hour and a lower rate between 1:3 and midnight, but the difference was significant only for Daubenton s Bat (Exact Binomial Goodness-of-Fit Test, two-tailed, p=.). Of the remaining species, only Soprano Pipistrelle had sufficient number of captures to discern a pattern and this showed no significant difference in capture rate First hour To midnight After midnight 4 3

4 Bats caught per trap or net Harp traps with lures versus mist nets: With a total of 55 trapping locations over the two nights of the BatMap weekend, it is interesting to compare the use of harp traps (with ultrasonic lures, generally placed in dense woodland away from rides and paths) and mist nets (without ultrasonic lures, generally placed across rides or paths or on probable bat commuting routes). There were 85 captures in harp traps and 57 in mist nets. However, one mist net was used with an ultrasonic lure, which complicates the comparison. Removing the results for this net gives a total of 85 captures from 19 harp traps and 49 captures from 35 mist nets. 1 out of 19 traps (84%) caught bats compared with only 3 out of 35 mist nets (%). A Chi-Squared test on the numbers caught, adjusting expected values according to the different numbers of traps and nets and using Yates correction, shows the difference to be significant (Χ = 45.5, p<.1). The pattern seems to apply across most species. Of the 5 Brown Long-Eared Bats caught, 8 were caught in nets and only in traps. However, eight of the bats caught in nets were caught in the one mist net which was used with an ultrasonic lure. After these bats are removed from the totals, a similar Chi-Squared test shows that significantly more were caught in traps than nets (Χ = 4.7, p<.5). The notable exception to the pattern was Barbastelles, all 13 of which were caught in mist nets. This is also a significant difference (Χ = 5., p<.5) Harp (lure) Net (no lure).4.. CP SP Natt Daub Brandt's Whisk BLE Barb Noc Despite the difference in capture rates, harp traps with ultrasonic lures and mist nets showed the same pattern of captures over the night. Summary of captures by time of night Bats caught by the net used with a lure are excluded. Harps + lures Nets Total First hour 1 (18.8%) 1 (.4%) (19.4%) To midnight 4 (54.1%) 3 (1.%) 7 (5.7%) After midnight 3 (7.1%) 9 (18.4%) 3 (3.9%) Total

5 Appendix 3: Locations of bat boxes 5

6 Bat boxes in Rushmere Country Park Red dots 1FF boxes; black dots FN boxes; black squares - Stebbings/Walsh wooden boxes.

7 Appendix 4: Ringing of Brown Long-Eared Bats During 15, 99 Brown Long-Eared Bats were ringed during bat box surveys and trapping sessions in King s and Baker s Woods, and there were 9 finds of bats already ringed, either earlier in the year or from the 13 bats ringed in King s Wood in 14. In King s Wood, a total of 14 bats have now been ringed, and over the two years of the ringing project there have now been 77 of these bats (47%) found again at least once. The netting and trapping of bats during the BatMap weekend in August gave an opportunity to investigate where bats forage in the wood as well as where they roost. In addition, 38 Brown Long-Eared Bats using boxes 7, 9 and 71 in Baker s Wood and Stockgrove were ringed. There have been only three recaptures of these bats, but the majority of them were ringed late in 15. So far, there has been no exchange of bats between King s Wood and Baker s Wood/Stockgrove. Finds of ringed Recaptures Brown Long- Ringed 1 1 recapture 77 Eared Bats in the recaptures 4 boxes have 3 recaptures 18 confirmed the 4 recaptures 5 three social 5 recaptures 1 groups of bats suspected from results in 14. The Eastern Group has used 1 different boxes on the east of the wood, with 54 bats ringed in 14 and a further 19 bats ringed in 15 (another possible box for this group is not confirmed). The Central Group has used 7 boxes in an area containing the main ride in the central core of the wood ( bats ringed in 14 and 14 more in 15). The Northern Group has been found only in 4 boxes in the north-western part of the wood (19 bats ringed in 14, 15 more ringed in 15). There have been no finds of individuals roosting in boxes used by a different social group from the one with which the bat was originally found. This is a remarkable demonstration of loyalty to the social group and to specific roosts. 4 bats ringed in 14 and a further 15 bats ringed in 15 cannot yet be assigned to a social group, either because they have been found only once in a box in the boundary area between two groups or because they were netted or trapped while foraging and have not yet been found in a bat box. Netting and trapping at the BatMap weekend has shown that these bats are not confined to their roosting areas when foraging there have been four instances of bats trapped while foraging well away from their roosting areas, in locations close to boxes used for roosting by another group. The map above shows boxes with ringed Brown Long-Eared Bats by circles (14) and squares (15). Blue - Northern Group, green - Central Group, red - Eastern Group. 7

8 Appendix 5: Locations of known roosts in buildings and trees since 1989 Red dots represent tree roosts, black squares building roosts and black triangles underground (hibernation) roosts. Labels indicate the species that have been found using the roost (BLE = Brown Long-Eared Bat; CP = Common Pipistrelle; Daub = Daubenton s Bat; Noc = Noctule; Pip. sp. = unidentified pipistrelle; Whisk/Brandt s = whiskered Bat or Brandt s Bat). Asterisks indicate roosts which are no longer used or have become structurally unsuitable. Roosts located as a result of the BatMap weekend are the Brandt s and Common Pipistrelle roost in the building west of Rushmere Lake, near to the southern edge of the map, and the roost containing a pipistrelle in Baker s Wood. 8

9 Appendix : Trees with potential roost features identified Trees with PRFs in Baker s Wood within the Country Park (left) and in the north-east of King s Wood (right). Grid squares are 1m. x 1m. in both maps. Examples of PRFs are shown in the photographs, both taken in King s Wood. On the left is a woodpecker hole, as used by Noctules, Daubenton s Bats and Brown Long-Eared Bats. On the right is a split in a branch. No such splits have been found to have bats present in Greater Stockgrove, but they are used by bats in other locations. Barbastelles, in particular, favour this type of cavity in trees. 9