Bailiwick Bat Survey

A citizen science project to map bats across the Bailiwick of Guernsey

Are you batty about bats?

We are looking for volunteers to help us map the distribution and activity of the different bat species across all islands of the Bailiwick. The survey season runs from early April until the end of October, so there is plenty of time to take part. Anyone can get involved – you do not need to be a bat expert! You can borrow a bat detector kit with all the instructions and equipment you will need from one of our Bat Centres in Guernsey, Alderney or Sark. Twice per year, you place it in the area you choose from our online survey map and it will automatically record the ultrasonic calls the bats make. After 3 or 4 nights recording, you then upload the recordings to our website, return the detector kit, and our automated sound analysis will identify each call and send you the results within hours! As a bonus, the analysis will also identify sounds made by bush crickets and small mammals!

We ask volunteers to select one (or more) 500x500m survey squares from an online survey map (there are 360 squares to choose from) and to survey your chosen square twice this year – once before the 15 July and once after 15 July.


Click the map to book your square(s)

Bat Centres

Once you have received confirmation of your square you can book a detector from the Guille Allès Library (Mon-Sat), the Guernsey Biological Records Centre (Mon-Fri), the Alderney Wildlife Trust (Mon-Fri, Sats until 12pm), or the Sark School (Mon to Sun by arrangement).


If you have any queries about the Bailiwick Bat Survey project or equipment, please email the coordinator.

Please do not contact the Bat Centres directly with questions.

Contact Bat Survey Coordinator Sarah Allez


Social Media

Quick Start Guide

Download the Quick Start Guide - it includes instructions on how to register for a BTO account, preparing for the survey, how to set the detector and how to upload the sound recordings for analysis


What do I need?

  1. A smartphone (iPhone or Android) 
  2. A computer with internet 
  3. An account with the BTO to upload the recorded sound files and receive your results! 
If you do not have a smartphone or computer, please email us & we can help.

When to survey

  • You will need to carry out two surveys – once before 15 July and once after 15 July
  • Each survey consists of 3-4 consecutive nights of recordings in your square

Survey steps

  1. Download the Quick Start Guide for instructions to register for a BTO account so you can upload your recordings, and instructions about the app you will need for you smartphone.
  2. Reserve your 500x500m square to survey using the online survey map.
  3. Once accepted by the coordinator, you will be emailed a link to book a detector to use. Ideally book for all of your surveys.
  4. Pick up your detector on your designated day.
  5. Get surveying! If you can please try and place the detector in the middle of the square, although we realise this is not always easy or possible.
  6. Upload the data from the detector’s memory card to your desktop/laptop computer using the memory card reader that will be in your pack.
  7. Once downloaded, our app will manage the upload of the sound recordings from your computer to our servers. This may take several hours to do.
  8. Return detector and all other equipment to us.
  9. Analysis of the sound data will take up to 12 hours (normally less than 2 hours) and results emailed to you.

The success of this project is dependent on volunteers picking up, using, and returning the detector to the bat monitoring centre as arranged.


Please let us know 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 problems with the equipment as soon as possible.

Top tips!

When to visit

Each booking slot allows for up to four nights of recordings in your square, any time between April and the end of October. These should be made on consecutive days. Unless the site is secure with no public access, please put the detector out at dusk and pick it up early in the morning  on each day to reduce the chance of the detector being stolen.



When the weather is bad, bats prefer to stay nice and cosy in their roost. The detectors are weatherproof but if the weather is truly awful (gale force winds / torrential rain), please do not survey bats.  If the weather is awful for more than 2 nights of your allotted period, please feel free to book additional survey days through the web system.


Placement of detector and microphone

Detector and microphone placement is critical for producing high-quality recordings. Please follow the below guidance as much as is practical:

  • Detectors should be deployed on the provided pole at least 5 feet (1.5 meters) in any direction from vegetation or other obstructions.
  • Several species avoid light, so please place the detector away from lighting (e.g. a house with lights) if possible.
  • Where close to water, avoid positioning the microphone directly next to water, to avoid noise reflection from the water’s surface.

Technical bits


How does the bat detector work?

The Wildlife Acoustics ‘Song Meter Mini Bat’ have settings that  record an hour before dusk and turn off an hour after dawn pre-installed on the detector. When it ‘hears’ a bat, or a small mammal or bush-cricket, it starts recording and saves a sound file (.wav file) on its memory card. These recordings are what we need to analyse to identify which species are present.

Why do I need a smart phone?

We need to know the exact location of where your bat detector is recording. To record the detector’s location we need you to download the Song Meter Mini Configurator [Android | Apple] to your smartphone so your phone can use its GPS to communicate, via Bluetooth, the exact location (latitude and longitude) to the detector


If you do not have a smart phone, the location can be entered manually when you upload the data to the BTO website.


How do I upload my recording to be analysed?

Once finished, take the SD memory card with recordings from the detector, and insert it into the supplied card reader or into an internal SD card reader, if you have one in your computer. You will need to install a small program, called the ‘Desktop Upload Client’, which manages the uploading of sound recordings (with information about the location and dates/times) for processing. It will download the sound files from the SD memory card to your computer and store them safely until your computer finishes uploading them to our servers for analysis.

  • When you reserve out a bat detector, you will be given a web link which will allow you to register/create a BTO Acoustic Pipeline account and then to add the Bailiwick Bat Survey to your account.
  • Once you have an account, log into your BTO Acoustic Pipeline account and click on the ‘Get the Desktop Upload Client’ web link.
  • Install the correct version (Windows or for Apple Mac) for your computer. Links are given for both.
  • The Desktop Upload Client will make a folder on your hard drive where recordings will be stored temporarily during uploading.


Q1. What is in the bat detecting kit?

The kit is contained in a small plastic box and has everything you need to undertake the survey. It contains full instructions (also downloadable here), the bat detector, a metal pole for mounting it on (the detector needs to be c. 7 feet up in the air), 2 sets of rechargeable batteries, a battery charger, an SD card reader to download the recordings to your computer to upload to us, and various other odds and ends.

Q2. How does the detector work?

The settings to record an hour before dusk and turn off an hour after dawn are already pre-installed on the detector. When it ‘hears’ a bat, or a small mammal or bush-cricket, it starts recording and saves a sound file (.wav file) on its SD memory card. These recordings are what we need to analyse to identify which species are present.

Q3. How long will it take to find out what species were recorded?

Once you upload the recordings, we hope to be able to get back to you with a summary of species recorded within a day.

Q4. Will 4 nights of recordings in a 500m square pick up all the species that use my square during a season?

Using previous surveys in the UK, we have learnt this amount of effort will give a good idea of the species present, whilst still allowing for broad coverage.

Q5. I have heard some species of bats are very difficult to identify from recordings. How well is the BTO Acoustic Pipeline able to distinguish species ? The pipeline will provide a first automated unverified analysis of recordings and return of results, but it can make mistakes. For this reason, further critical manual checking of the results will be carried out at the end of the season.

Q6. I have had a problem trying to reserve my square using your online map. What can I do?

If you have a problem, please email us directly at, letting us know what square or squares you are interested in covering. Each square has a unique reference number (e.g. WV3178NW) which can be seen when you double click on a square in the online square sign up map.


Q7. How can I help the bats in my areas?

There are a few simple things you can do to help that bats in your area:

  • Reduce pesticides – all bats that live in Guernsey eat insects. You can help feed them by minimising your use of pesticides
  • Promote natural habitats – leave non-hazardous dead or dying trees, they make great homes for bats.
  • Put up a bat box – they are an easy homes for bats to rest
  • Avoid disturbing bats – If a bat is disturbed during hibernation, it may become active and burn through its fat reserves.