Survey methods

Your bat square                                                                               

We ask that you request a 1-km square/s (e.g. TG1243) to survey through our Norfolk sign up map.

After you have requested a square, you will automatically be emailed a link to a web site, where you can book and borrow a detector to use for the survey from a Norfolk Bat Monitoring Centre of your choice.

You may need to ask permission to access private land on your square, and a standard letter requesting access can be obtained.

The most valuable information comes from squares that are surveyed over a number of years, as this consistency allows bat distribution and numbers to be accurately compared.  We would therefore be pleased if you could consider your 1-km square a long-term project.

Importantly the success of this project is dependent on volunteers picking up, using, and returning the detector to the regional bat monitoring centre as arranged.   Please return the detector if you are unable to carry out a survey, so there are not periods when the detector is not being used.   Please also report any problem with the equipment as soon as possible.

Where and when to survey

Recording form – When you borrow the equipment, this will include a field recording sheet.  It is extremely important that the field recording sheet is completed and returned to the BTO using the supplied FREEPOST envelope, along an equipment check-list with the SD memory card containing recordings in the provided plastic storage case when you have completed the survey.

The field recording sheet will ask you to record the dates that the detector was left out to record, and the grid reference (point location) identifying where the detector was left out to record on each night.

If you have a GPS, please use this to determine the grid reference to show where the detector was left out each night, or use the quick map viewer to allow us to identify (as closely as possible) where the detector was left out on each night, but substituting ‘TL8585’ with the grid reference for your own square.   Where possible please record an OS grid reference e.g. TL 85015 86014 (ideally a two letter, ten number grid reference).

Your survey points – Please choose three different points to survey within your 1-km square.   Ideally the three survey points should be placed at least 200 meters apart, although we allow for some flexibility in remote areas.

When to visit – The three survey visits (nights of recordings) to a 1-km square can be carried out any time between May and the end of September. For logistical purposes, we suggest that the three visits (nights of recordings) to different points within a 1-km square are made on consecutive days.     Unless the site is secure with no public access, please put the detector out at dusk and pick it up at first light, to reduce the chance of the detector being stolen.    We advise all volunteers to read our leaflet – Health and Safety for Volunteer Fieldworkers.

Weather – Please do not survey bats in persistent heavy rain, strong wind or if the nightly temperature is predicted to fall well below 7oC, which would significantly reduce your chances of recording bats.   You can check the nightly temperature by entering the name of the closest town in the Find a Forecast section on the BBC weather web site. Note: depending on the weather you may want to book additional survey days through the web system. However please ensure that the detector is not already booked for these days.

Where bad weather intervenes, it may not be possible for the three survey nights in a square to be consecutive.  It is important, however, that all three surveys are completed. Please re-book replacement nights for the first available opportunity but it will not matter if several weeks elapse between surveys.

Detector and microphone placement – Detector and microphone placement is critical for producing high-quality bat sequences for later analysis. Whilst not always practical ideally:-

  • Detectors / microphones should be deployed at least 5 feet (1.5 meters) in any direction from vegetation or other obstructions.
  • Place away from lighting (e.g. a house with lights). This is likely to reduce the diversity of species recorded, where several species avoid light.
  • Where close to water, avoid positioning the microphone directly next to water, to avoid reflection from the water’s surface.
  • Because bats will often follow linear landscape features like hedgerows or tree lines and are attracted to water, we recommend that detectors are placed adjacent to these features where possible.