Can Passive Acoustic Monitoring of Birds Replace Site Surveys?

Posted byKeiron Derek BrownPosted inBiological recording, Blog, Virtual Symposium, Wilder SensingTags:, , , , ,

The technology used for monitoring the bioacoustics of a site is constantly evolving, with improved hardware, advancing software and growing use of Artificial Intelligence.

Are we heading towards a situation where using sound recorders to passively monitor a site for birds can replace the need for site surveys with human field surveyors?

This blog features presentations from a technology specialist and ecologist, exploring the benefits and limitations of undertaking passive acoustic monitoring of birds on a site. We delve into how these two methods can complement each other and hear case studies where passive acoustic monitoring has been used alongside traditional site surveys.

This blog features two guest presentations:

  1. Wilder Sensing: An Ecologist’s Perspective with Kate Downes (Ethos Environmental Planning)
  2. Wilder Sensing: Innovative Technology To Support Ecologists with Geoff Carss (Wilder Sensing)

Wilder Sensing: Innovative Technology To Support Ecologists

Geoff Carss (Wilder Sensing)

Wilder Sensing is a biodiversity monitoring and reporting tool that uses commercially available sound recorders to record soundscapes, processes the files using Artificial Intelligence to identify what species are present and provides easy-to-use analytic tools to understand the large datasets generated. This enables vast quantities of audio data to be captured and analysed at low cost to ecologists for both short and long-term surveys.

This presentation explores the practicalities and process of bioacoustics together with the results that can be achieved. Geoff Carss will explore some of the issues and limitations such as false positives and negatives, exclusion of under-reported species and bias depending on the species and how to mitigate them. He will also cover how to get long-term time series data sets, how monitoring in urban and industrial environments can cause bias due to background noise and how different filters can limit the identification of scarce species. This session will include a demo of Wilder Sensing where some of these issues will be explored.

Useful links

Q&A with Geoff Carss

  1. Does Wilder Sensing only work for monitoring birds?
    We’ve started with birds as we wanted to develop the model to work well for a single group before branching out. The tool can be used for other groups, but we first need to develop a model for dealing with the sounds created by these groups. The obvious next group would be bats and developing a model to deal with the ultrasonic calls made by various bat species. We’ve been undertaking work to investigate if the tool can be used for specific target species, such as Water Vole, and I’ve got some fantastic recordings of eels using hydrophones that we’re working on. There is also the fascinating emerging subject of soil acoustics, and other organisations looking at pollinator acoustics. The possibilities are vast, but in order for us to produce meaningful outputs we need to first understand the sounds made by various groups and then develop a model to recognise and interpret these.
  2. Do you believe that, with further development, bioacoustics can be used to get measurements of abundance?
    We’ve been recording on one particular site for over two years now. It is a site that has been “re-wetted” and the site managers are interested in how this has impacted the use of the site by Lapwings. We wanted to use the relative frequency of calls as a very rough approximation of abundance, with it being obvious when a flock of Lapwings arrive on the site. We hoped to be able to detect if more flocks were using the site for longer for winter feeding. However, this winter was so wet that the Lapwings were anywhere near the recorder due to the area being flooded out. A direct comparison using core frequency for abundance is pretty sketchy so we’re looking into the benefits of using triangulation, using multiple recorders to establish a measure of abundance. This will be quite the same as what a field surveyor would detect, but it’ll be interesting to see the results of using triangulation.
  3. How much would it cost to get started?
    We’ve deliberately set this up with a simple cost model. We charge a reduced rate of £400 per year for the analysis of data for one recorder for individuals, NGOs and charities. For ecological consultants and other for-profit businesses, we charge £800 per recorder per year. This includes covering the main cost associated with collecting this much data: the storage. We are constantly updating the tool. We don’t provide recorders, but you can use any recorder (such as the Song Meter Micro 2). We are always happy to chat over the Wilder Sensing tool and encourage anyone interested to get in touch.

Wilder Sensing: An Ecologist’s Perspective

Kate Downes (Ethos Environmental Planning)

Traditional field surveys are essential for understanding which species of bird are present on a site and how they are using it. However, these surveys only provide a snapshot in time and are limited by cost and field surveyor availability. Bioacoustic monitoring can monitor a site year-round but may miss things that field surveyors would detect. Kate discusses how Ethos Environmental Planning has developed a hybrid programme of bioacoustic and field surveys for undertaking ornithological site monitoring.

Kate Downes is an Ecologist at Ethos Environmental Planning and an Associate Member of the Chartered Institute of Ecology & Environmental Management. Kate’s specialism is ornithology, in her role at Ethos she leads the design and implementation of bird surveys across the seasons. Her previous work includes studying the Mauritius Kestrel as a field biologist and current work with barn owls helping the South Glos Owl and Bird of Prey Conservation Group (SGOBPC) monitor the species.

Useful links

Q&A with Kate Downes

  1. How does the bioacoustics approach compare financially to the traditional field survey approach?
    That’s an interesting question, and not as straightforward to answer as you might think. We employed a hybrid approach, so we were using Wilder Sensing to complement our field surveys and this past year has very much been a trial for us. For smaller sites, it probably worked out cheaper as we were undertaking fewer field surveys and using the acoustics analysis to inform our reports. For the bigger sites, the recorders were an additional monitoring aspect on top of the usual field surveys and therefore were an additional expense, but gave us so much more data and enabled us to produce more robust reports.
  2. Did you just use Wilder Sensing to analyse the acoustic data, or did you also undertake analysis?
    We only used Wilder Sensing for the projects that I referenced in my talk. However, we did have a validation process for the data provided by Wilder Sensing. For example, if Wilder Sensing included a record of a Curlew at a site where this seemed unlikely we would check that using our own knowledge of as well as other bioacoustic analysis software.
  3. How many recorders would you need for different habitats?
    The guidance mentioned in the talk (see the links above) provides information on this and brings together all of the literature and experiments on this. There are lots of different things to consider here, including cost as each recorder and the data it produces has a cost associated with it. We set all of our recorders a minimum of 250 metres apart to reduce the chance of double counting as advised in the guidance.

Wilder Sensing ecoTECH blogs

  1. How Can We Use Sound to Measure Biodiversity: https://biologicalrecording.co.uk/2024/07/09/bioacoustics-1/
  2. Can Passive Acoustic Monitoring of Birds Replace Site Surveys blog: https://biologicalrecording.co.uk/2024/09/17/bioacoustics-2/
  3. The Wilder Sensing Guide to Mastering Bioacoustic Bird Surveys: https://biologicalrecording.co.uk/2024/11/26/bioacoustics-3/
  4. Bioacoustics for Regenerative Agriculture: https://biologicalrecording.co.uk/2025/03/31/bioacoustics-for-regen-ag/
  5. AI-powered Bioacoustics with BirdNET: https://biologicalrecording.co.uk/2025/07/08/birdnet/

Event partners

This blog was produced by the Biological Recording Company in partnership with Wilder Sensing, Wildlife Acoustics and NHBS.

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Published by Keiron Derek Brown

A blog about biological recording in the UK from the scheme organiser for the National Earthworm Recording Scheme.

2 thoughts on “Can Passive Acoustic Monitoring of Birds Replace Site Surveys?”

  1. Pingback: The Wilder Sensing Guide to Mastering Bioacoustic Bird Surveys – Biological Recording
  2. Pingback: Bioacoustics for Regenerative Agriculture – Biological Recording

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