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bat passes of any species in total (the highest levels of activity recorded) on one night were surveyed whilst light levels were still high enough to see the bats.
The rationale was that the surveyors could observe whether the activity is either lots of bats commuting from a roost early on in the evening (generally all travelling in the same direction), or smaller numbers of bats making repeat passes (going backwards and forwards foraging along the hedge). All surveys commenced 15 minutes before sunset and continued until 1.5 hours after. Two surveyors surveyed each location and were positioned at either end of the liner feature. Dates, times and weather conditions recorded are given in Table 2. below.
Table 2: Dates, times and weather conditions recorded during manual activity surveys
Date
Sunset Time
09/07/2012 21.14 11/07/2012 21.13
Start Time
21.00 21.00
End Time
22.50 22.27
Temp at start
15.8 14.2
Temp at end
15.1 13.5
Cloud cover at start
3 3
Cloud cover at end
6 8
Wind speed at start
0 1
Wind speed at end
0 4
Rain conditions
0%
Rain at end of survey
Emergence surveys were conducted by RSK personnel trained and experienced in carrying out such surveys, including Paul Barnes and Sarah Brooks.
Frequency division and time expansion bat detectors (Duet and Pettersson) enabled surveyors to accurately identify most bat species by their unique echolocation calls. Identification was confirmed where necessary by recording bat calls onto minidisk or digital Edirol R-01 recorders and analysing the calls using BatSound software. Further methods of identification included observation of bat flight pattern and behaviour.