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Teil  C  -  Annex

5  Bats
See  Table  5.1  :  Survey  of  bat  migration  activity  in  the  offshore  area.
Process  instruction  for  survey  of  bat  migration  activity  in  the  offshore  area  of  the  Baltic
Sea.
Scope  of  application
The  process  instruction  should  be  seen  as  a  guideline  for  the  qualitative  survey  of  bat  occurrence ­
  and  for  the  relative  estimate  of  bat  activity  in  the  assessment  area  during  bat  migration
times.  In  the  Baltic  Sea  region,  bat  migration  is  expected,  depending  on  the  species,  in  the
period  from  mid-April  to  mid-June  and  mid-August  to  end  of  October  (e.  g.  Ahlén  1997,  Seebens
  et  al.  2013).
So  far,  the  knowledge  base  for  correct  offshore  monitoring  of  bats  is  limited.  This  process  instruction ­
  is  a  first  step  towards  standardised  survey.  It  will  be  evaluated  and  reviewed  with
further  development  of  the  StUK.
The  survey  of  bat  fauna  is  carried  out  in  the  style  of  the  night-time  call  survey  of  migratory
birds  (of.  Table  3.2.2)  and  comprises  the  acoustic  recording  of  écholocation  calls.  The  probability ­
  of  recording  these  calls  depends  on  the  species-specific  call  “volume”  and  on  the  technical ­
  characteristics  of  the  used  acoustic  detectors  (frequency-dependent  sensitivity,  directional ­
  characteristic)  (e.  g.  Adams  et  al.  2012).  Most  species  or  species  groups  can  be  identified
on  the  basis  of  their  call  characteristics  (species  spectrum).  The  number  of  bat  call  sequences
provides  information  regarding  their  relative  activity.

Equipment  for  recording/analysis  of  bat  calls
The  survey  system  presented  below  follows  the  Avisoft  system.  If  other  survey  systems  are
used  in  the  context  of  offshore  surveys,  it  must  be  ensured  that  they  comply  with  the  minimum
requirements  and  equipment  standards  presented  here.
The  survey  system  must  fulfil  the  following  minimum  requirements.  It  must  be  noted  that  only
detector  systems  with  a  high  sensitivity  range  of  16-25  kHz  are  permissible:
Bat  detection  system:
•  Bat  call  recording  per  second
•  Real  time  recording
•  Minimum  sampling  rate  300  kHz
•  External  microphone  port
•  Calibration  possible
•  Option  for  bat  call  filter
Microphones:
•  External  ultrasound  microphones  (e.  g.  Knowles  FG  Electret  Ultrasound  or  CM16/  CMPA)
•  Shielded  microphone  cable  with  shielded  5-pin  XLR  connector
•  Waterproof  microphone  cover  (e.  g.  plastic  tube)
•  Signal  generator  for  testing  functionality  and  for  regular  calibration
•  Microphone  heating  (Note:  microphone  heating  has  the  advantage  of  reducing  condensation ­
  and  thus  salinisation  of  the  microphone)