Nathusius pipistrelle survey - results of 2009 pilot survey
In September 2009, 74 volunteers took part and data were received from 82 sites. A big thank you to everyone who took part and helped make this pilot survey such a success.
At 37 sites the standard survey method was carried out of identifying Nathusius’ pipistrelle in the field in heterodyne mode whilst making frequency division (or in a few cases time expansion) recordings that enabled sound analysis to be carried out in order to verify the field identifications. Sound analysis was focussed on walks and spots where “Nathusius’ pipistrelle”, “Unsure Nathusius’ pipistrelle” or “Other pipistrelle species” were identified in the field in heterodyne mode.
At 16 sites FD detectors only were used (e.g. BatBox Baton or Anabat) which do not tend to enable instant identifications to be made in the field, so for these sites all walk and spot files were analysed to check for Nathusius’ pipistrelle.
At 27 sites heterodyne detectors only were used and the volunteers simply followed the instructions for identifying this species in heterodyne mode. This method does not enable recordings to be made for verification.
At the remaining 2 sites survey forms were sent in but it was unclear which system had been used.
Nineteen volunteers analysed their own recordings using a standard protocol. BCT staff carried out verification on volunteers’ sound analysis and were largely in agreement with the results. All recordings not analysed by volunteers were analysed by BCT staff.
Nathusius’ pipistrelle records were submitted from 24 of the 82 sites (29%). This figure includes unverified heterodyne records as well as broadband detector records that were able to be verified. Nathusius’ pipistrelle presence was verified through sound analysis at 14 sites (17%). Sites with unverified records will be a priority for revisiting with recording equipment in 2010. Equipment will be available for loan to volunteers on request.
Distribution of sites monitored as part of the pilot Nathusius' pipistrelle survey in September 2009.
Verified records are from surveys where recordings were made and Nathusius' pipistrelle presence was confirmed through sonogram analysis.
Unverified records are from heterodyne detectors. "Unsure" records could possibly be common pipistrelles calling at the lower end of their frequency range. A target for 2010 will be to make recordings at all sites with unverified records to enable verification to be carried out.
The aims for the September 2010 survey are:
Repeat the sites surveyed in 2009 in order to begin building up repeat survey data.
Add new sites to the site network in order to build up a more comprehensive picture of species distribution and increase the sample size for future analysis.
- Increase the proportion of sites at which recordings are made in order to verify Nathusius' pipistrelle presence and collect data on other species at lakes. A limited number of frequency division detectors and recording equipment will be available for loan to volunteers to help achieve this.